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PREFACE. 

'his publication has been called for by many inquiries addressed 
to the Editor of " COMPRESSED AlR " asking for various papers, 
some of them original and others compiled, which have been pub- 
lished in that little magazine during the first five years of its 
existence. 

The supply of the early issues having been long since exhausted 
and the demand continuing, an effort has been made to present in a 
single book of reasonable size all the important practical informa- 
tion contained in the first five volumes. 

No attempt has been made to introduce new matter, but the 
various papers, editorials and notes have been selected and arranged 
under suitable headings so that any one seeking information on this 
subject may be afforded facilities for finding it properly classified. 

The principal claim to recognition rests on the practical char- 
acter of the material, as the little magazine from which these papers 
have been compiled has endeavored to record the every-day experi- 
ences of engineers familiar with the handling of compressed air 
apparatus. These experiences cover a wide field and are not simply 
the opinions of a few men, but those of many, hence it is believed 
that the collection of this data in one book will prove of service to 
the engineer and student. 

Full credit is given to the different authors for all abstracted or 
contributed articles, and the editor wishes to acknowledge his in 
debtedness to Mr. J. J. Swan for his valuable assistance in compiling. 

New York, Jan. 12, 1903. W. L. SAUNDERS. 



PRODUCTION. 



AIR POWER. 

The power of air is shown in the cyclone and whirlwind uprooting the 
stanchest trees and exhibiting a power that has been estimated to be beyond any 
that is within the control of man. 

The power of air is shown when the sail of the ship is made to drive thou- 
sands and tens of thousands of tons weight through the waves of the sea. What 
power has done greater service to mankind than this? Air power has been the 
means by which continents have been discovered and populated. It has done more 
for civilization than most of us realize. 

The power of air when applied to the rock drill is shown in the building 
of great tunnels and in the development of mines. The "Hoosac," "Sutro" and 
New York Aqueduct Tunnels would have been almost impossible but for com- 
pressed air. The great piers of the Brooklyn Bridge required compressed air in 
the caissons to enable them to reach solid rock foundations. By no other means 
known to engineers could this bridge have been built ; and so with most of the 
great bridges and tunnels of the world. 

The power of air is shown in the Bessemer converter and in the blast 
furnace producing iron and steel, the most useful metals known to mankind. 

Air power is shown in the brakes on the train, when hundreds of tons, 
moving fifty miles an hour, are brought to a standstill within a few hundred feet. 
Think of the power required to do this ! The little air compressor perched on the 
side of the great engine brings all this about. Think of the lives that have been 
saved by the air brake ! 

The power of air is shown in the gas engine which uses a combination of 
air and gas as an explosive mixture of great force. The hot air engine produces 
power with air alone. 

Air power is used to move railroad switches and signals more than twenty 
miles from the source of supply. Air hoists, air jacks and air lifts are valuable 
auxiliaries. Water is raised from subterranean sources and delivered to the reser- 
voir by compressed air. The power of air drives the shell from the dynamite gun. 
Granite is cut and carved by the pneumatic tool. Air power is used to raise 
sunken ships. The fall of water converted into air power is used miles away to 
produce useful results. 

Air power in shops is used to clean castings, for punching, caulking, tap- 
ping, drilling, reaming, chipping, riveting and painting. 



As an interested reader of your magazine, I find its terse and pithy articles 
have the effect of sharpening my appetite for more information concerning the 
subject of Air Power, which to the non-expert, like myself, is like an "undis- 
•'overed country." A host of questions arise in my mind, suggested by your 



' 



6 PRODUCTION. 

magazine. But I venture now to ask one which is purely scientific and funda- 
mental, viz: In compressing air, why is it that heat is generated, or, to put it 
conversely, why does the heating of air expand it? 

Doubtless these questions may seem to you very simple, but I am free to 
admit, that while I have a theory about this matter, I cannot prove it scientifically. 

NEW YORK. INQUIRER. 

Our correspondent asks two questions — i. Why is it that heat is generated? 
and 2. Why does this heating expand the air? 

1. In compressing air, heat is produced because the piston does work upon 
the air which, being confined, does no work in return; hence there is a direct con- 
version of work into heat. We do not believe that there is any such thing as 
heat, but that what we call heat is the sensible effect of vibration. A moving 
piston, being the vibration of a mass, may be converted into moving molecules of 
air. Prof. Tyndall, in his book "Heat a Mode of Motion," illustrates the point by 
dropping a lead ball from the ceiling to an anvil on the floor, heat being pro- 
duced and measured in the ball. "The motion of the lead," says Prof. Tyndall, 
"as a mass has been transferred to the atoms of the mass, producing among them 
the agitation we call heat." It is following this law of nature that heat is pro- 
duced when a target is struck by a shot. In the fire box of a locomotive wc pro- 
duce heat which is converted through the boiler to the engine and into the m.o- 
tion of the train. This motion may be converted back again into heat and the train 
brought to a standstill by friction in the axles, and this result is sometimes 
brought about by hot boxes on a train. 

2. Heat expands air as it affects almost all bodies. It is supposed that this 
expansion is caused by the increased vibration acting to pull apart the atoms ox 
the substance. It tends to destroy the cohesion in the particles. 



EARLY PNEUMATICS. 



The application of the old time-honored saying, "There is nothing new 
under the sun," meets with no more striking illustration than in the harnessing of 
that mighty element— the air— to do man's bidding. 

The seventeenth century demands and very justly merits our warmest 
admiration for one of its great inventions, the "air pump," and its creator, the 
famous burgomaster of Magdeburg, Otto von Guericke, was the wonder of his 
age; yet we are told that Galileo, not long before, made the discovery of the 
underlying principle of that and all such experiments, namely, that air is ponder- 
able. However, could these and other great scientists have suspected that their 
knowledge was antedated more than a thousand years by a certain Heron of 
Alexandria, who lived, invented and died under the mummied Ptolemies, Phila- 
delphus and Euergetes, they would doubtless have been not a little disconcerted. 
But they had no means of obtaining such information— happily for the peace of 
mmd of their shades— for it has only been in recent years that any knowledge of 
the Egyptian inventor has come down to us, and this through such rare channels, 
that in a treatise by a noted French "savant," M. Duteus, on the "Origin of Dis- 
coveries Attributed to Modern Inventors," a work in which the author tries to 
make the best possible case for the Ancients, the name of Heron is not even men- 
tioned. 



PRODUCTION. 

^Of late, however, the investigation of some of Heron's discovered writiogs, 
scanty as they are, and the finding of a few scattered notices bearing on his won- 
derful inventions, have developed a keen interest in their author, and established 
his claim to be ranked with the leading lights of the world, among men of science 
and antiquaries in generaL 

Nothing is known of his life beyond the facts that he flourished between 
284 and 221 B.C., and that he was the pupil of Ctesibus. Even his name is 
shrouded in mystery, so that while some speak of him as Heron, others feel 
justified in omitting the final "n." A certain popular celebrity has accrued to his 
name through the common pneumatic experiment called "Hero's Fountain," in 
which, as every student of Natural Philosophy will remember, a jet of water is 
sustained by compressed air. 

Another claim to recognition is a steam engine of his invention — one spoken 
of at some length in his writings. This remarkable machine worked precisely on 
the principle of "Barker's Mill." A boiler with arms having lateral orifices is 
made to revolve around a verticle axis. The steam issues from the lateral orifices, 
and the uncompensated pressure upon the parts opposite the orifices turns the 
boiler in the direction opposite to that of the issue of the steam. 

Still another engine described in Heron's Pneumatics, has also a double 
forcing pump used for a fire engine, and various other applications of the elasticity 
of air and steam have all tended to secure him that position In the scientific world 
which has been attained by a few of the Ancients and- is unanimously sustained 
by the cheerful readiness of us Moderns to recognize, appreciate and applaud the 
"divine spark" when discovered not only in our own times, but over the lapse of 
centuries. 

At a time when a work on "the Seven Wonders of the World," was 
more or less a record of contemporaneous history but with just enough flavor of 
antiquity to make the era of 250 B. C. seem comparatively young and progressive 
— in that complacent, tolerant way, with which human nature is wont to view 
past achievement In the light of present possibility — Philon of Byzantium wrote 
his "Ancient History," recorded the work of his beloved Master Ctesibius, chron- 
icled some truly marvelous discoveries and inventions of his own and completed 
the mission of his destiny on the field of battle, 212 B. C. 

His descriptions of "The Hanging Gardens of Assyria," "the Pyramids of 
Egypt," "the Statue of Jupiter Olympus," "the Colossus of Rhodes" and all the 
other wonderful creations of the early genius of man, which constitute the world- 
famous "Seven Wonders,' are set forth with a grace and elegance worthy of pres- 
ent imitation, but, In many places, with a too-studied regard to rhetorical effect 
which robs the writings of that directness of simplicity without which no work 
can hope to live. In its first freshness forever. Therefore, it is that musty book- 
shelves and worm-eaten tomes must be consulted to learn of Philon the "litera- 
teur" — but Philon the mechanician and ancient authority on the besieging and 
defending of cities, seems quite another personage. 

Two of his books on military engineering, are on the general subject of 
the manufacture of missiles, while a third covers a wide range, including the 
arming of harbors, the use of levers and such mechanical powers, as also other 
contrivances connected with the storming and resisting of towns. In the latter, 
he advocates a strange and barbarous system of warfare, advising that on the 



8 PRODUCTION. 

appix>ach of the enemy through an open country, all springs and grain be pois- 
oned. For this policy, even in ancient times, he was severely censured. 

But modern attention has been directed to him chiefly through his notice 
of an invention of Ctesibius — that master mind, for the sake of whose teachings 
Philon left his home and removed to Alexandria to become, like Heron, his in- 
structor's devoted disciple. 

This invention was an instrument of war, and consisted of a tube out of 
which an arrow was shot by means of compressed air. This is one of the oldest 
applications of that mysterious force, the modern air-gun being an evolution of 
Ctesibius' ingenious machine. 

Over sixteen centuries elapsed between the first invention and the next 
model, and in 1560 we find that the new gun had a butt end of hollowed metal 
containing a reservoir in which air was compressed by means of a force pump. 
The balls were placed in the little receptacle, which was furnished by a stop-cock, 
and as one shot was sent off, the stop-cock was opened and a fresh projectile in- 
serted. Naturally, the force of projection diminished as the reservoir of com- 
pressed air emptied, so that after every few discharges, it became necessary to 
re-compress the air. 

Some years later this model was improved upon, but even in its best form, 
it has left much to be desired in point of time saving, and furnishes a golden op- 
portunity to some nineteenth century genius to make the air-gun a more deadly 
weapon than its rival in fire-arms — or better still, to devise a machine of such 
dimensions that so vast a quantity of air could be compressed within it, that its 
liberation would annihilate the largest army ever massed together iamong the 
nations. 

Thus might the possibility of war be averted by the appalling consequences 
of facing an unchained element m.ade obedient to tli^ operation of a single in- 
dividual. 

That genius of human progress who presides over the rapid supplying of 
man's needs, passing over electricity, water and steam, selects air as the force 
best adapted to serve his ends. 

This benign spirit appeared in the person of a certain Dr. Denys Papin, 
who lived nearly two centuries ago in the quiet town of Blois, and under the rule 
of "le grand monarque," in beautiful France. 

To this distinguished Frenchman we are indebted for the first suggestion 
of conveying compressed air through pipes as a means of transmitting power; 
and toward the end of the century, his fertile brain conceived the idea of pro- 
jecting parcels through a tube by means of compressed air. Never before, in the 
history of inventions, did the application of this principle to such an end take 
form in the minds of the world's great scientists. Dr. Papin, therefore, stands to- 
day as the pioneer in that field. 

After the death of the doctor, we are told, the invention took a sleep of a 
hundred years— which might be a long sleep for anything else, but is, for an in- 
vention, only a reasonable nap. 

We do not hear again, therefore, of any atmospheric system of propulsion 
until 1810, when George Medhurst, a mechanical engineer, took out a patent in 
England "for a means of conveying goods, letters, parcels and passengers by 
means of a tube and a blast of compressed air." 



PRODUCTION. 9 

In the same year he published a pamphlet on "A New Method of Conveying 
jtters and Goods with Great Certainty and Rapidity," in which appear the first 
Practical suggestions for the introduction of what is now known as the "Pneu- 
latic System." This work foreshadows almost everything since discovered in 
mnection with the subject of air propulsion. 

A little later in the year appeared another pamphlet by Medhurst, entitled, 
*A System of Inland Conveyance for Goods and Passengers." In the latter, un- 
jfortunately, the zeal of the inventor carried him beyond his limitations, and as a 
result, he made a failure of the car system — as, indeed, did Vallence, his English 
rival, and Pinkus, a clever American., 

However, the system for conveying light goods, such as letters, parcels, etc., 
iroved a complete success, and now in its perfected form it operates by connecting 
le tubes containing the carriers, one with a vacuum chamber and the other with 
compressed air chamber, air being condensed behind the carrier in one and ex- 
hausted before it in the other at the same time by a double-barreled air pump, 
operated by an engine of one horse-power and attaining a speed of about forty 
miles an hour. 

The first line of this system was controlled by "The Pneumatic Dispatch 
Tube Company" of London, in 1859, between Euston Square Station and the Post 
Office in Eversholt street, later extending its charter to Holborn. ' The entire 
distance covered is 3,080 yards, laid with easy gradiants. 

The telegraph offices of London were the next to eagerly adopt the new 
system for communicating with the central office. At each way station of the line 
is a receiving apparatus consisting of two short barrels, parallel with the main 
tube, either of which may be put in or out of connection with the line by means 
of a lever ; one of these is open at both ends so as to allow a carrier to pass 
through unimpeded, but the other is almost entirely closed at one of its ends, so 
that when it is switched into line with the main tube it intercepts the carrier. 
Of course, the time when a carrier is expected to arrive is telegraphed to the re- 
ceiving station. 

To-day every great city in the world has its commerce facilitated by this 
ingenious device ; and it would require only a little time and thought on the part 
of the inventors of this age to perfect the passenger tube to such an extent as to 
make a luxurious pneumatic railway solve the burning question of transportation. 

At first electricit}'^ dazzled the scientist and inventor by the fascination of 
her indefinite and mysterious possibilities, but the silent depth and power of her 
equally fair sister, compressed air, is now taking so firm a hold upon the imagi- 
nation and judgment of the thinkers of to-day, that she bids fair to outstrip her 
rival in the race for dominion. 

One of the first applications of the force of compressed air in this century 
was the pneumatic dispatch tube, and its inventor, George Medhurst, was re- 
garded by his English compatriots as occupying an unenviably conspicuous posi- 
tion on the Vv'rong side of that partition which, according to the poet, divides 
great wits from madness. 

The success of his tubes for the conveyance of letters and light parcels, 
however, completely vindicated him from all taint of mental unbalance, and even 
though he failed in establishing an effective pneumatic railway in Great Britain. 



lo PRODUCTION. 

the Britons ended by admiring the man and standing in respectful attitude 
before the unlimited possibilities of the force. Indeed, such a hold did this power 
gain on the English mind that a proposition was considered by the Government 
of connecting Ireland and England by the "Pneumatic Dispatch Tube System," 
laid beneath the waters of the Irish Channel in order to facilitate and expedite 
mail carrying. But the times were not ripe for its perfection, so the operations 
of the plan were suspended. 

However, a line between the London and Glasgow telegraph stations was 
established, and an amusing anecdote is told of how an American at the Scot- 
tish town, who afterwards wrote his experience to the "Boston Transcript," first 
made acquaintance with the system. 

Thinking that an error had been made in the transmission of his message 
to London, the gentleman in question desired to see the original blank. The 
operator, with an amused smile, told him that his message was then at the Lon- 
don main office. Pie replied, "Yes, yes, 1 know; but I want my own copy that 
I wrote out here about a half an hour ago." The clerk answered, "I understand 
what you mean, sir; but your copy has been in London for the past half hour, 
and if you will step here and apply your ear to this opening, I think I can con- 
vince you, in a few .seconds, of the truth of my statement and show you your 
message." The operator then sent a dispatch, and presently the astonished lis- 
tener remarked a peculiar whirring sound, and — he writes — "seventeen seconds 
later I heard the tinkling of a little bell announcing the arrival of the carrier, 
close at my ears, and in a moment more I had my original message in my hands." 

He straightway became an ardent disciple of the new system, and led, 
doubtless, by the enthusiasm which characterizes most zealots, the American gen- 
tleman made several small misstatements, among them that of the time said to be 
consumed between the London and Glasgow stations. In point of fact, the car- 
rier would have been required to attain a speed of four miles a second in order 
to cover the distance in question, and would have, moreover, been rendered red 
hot before the expiration of the first second. But allowance must be made for 
all converts, and as he was correct in his essential statements, let the mantle of 
charity, by all means be extended. 

Since the success of Medhurst's invention, America, that liberal patron of 
the best in every branch of advancement has lent her encouragement to all new 
applications of the magnificent force of compressed air, and as a result, we have 
our coal and gold mined by this power, canals dug, rocks drilled, sunken vessels 
raised, sheep sheared, carpets dusted, cars cleaned, clocks and sewing machines 
run, ships steered, locomotives propelled, stone carved, and street railways 
operated. One is therefore constrained to ask, "Could electricity do more?" 

FRANCIS MALOY. 



VIEWS OF A NON-EXPERT. 



These remarks are presented as the views of a non-expert, who has, never- 
theless, been impressed for years with the possibilities of compressed air as a 
motive power in conjunction with an adequate mechanical medium. 



-m 



PRODUCTION. Ti 

The present advanced development of the power was foreshadowed from 

the beginning of the century ; but the knowledge of the latent force of air in this 

mdition far antedates even that period. As with nearly all the great powers of 

'ttiodern science and mechanics, progress has gone by slow and painful steps, 

through many failures, many apparently insurmountable difficulties, into the 

region of practical, urviversally acknowledged success. 

The best known compressed air engine in the early years of the century 
was that invented by Dr. Sterling and his brother, James Sterling, C. E., of Edin- 
burgh, Scotland, in the year 1816. The air was compressed for this machine to 
the pressure of from eight to ten atmospheres but, as in the case of the early steam 
engines, the machine was not a commercial success. It had the effect, however, 
of stimulating interest and invention. 

Captain Ericsson, who had not yet come to the United States to begin his 
work of revolutionizing modern war vessels, took up the idea and at length pro- 
duced a working machine. It differed from Sterling's in being of much lower 
pressure. Its bulkiness, in proportion to power, and the intense heat evolved, were 
serious defects and rendered it only another link in the chain of experimentation. 

In 1867 Sir George Cayley and Philander Shaw showed a machine at the 
Paris Exhibition of simple construction and greatly increased power. In this 
machine the compressed air was delivered into the furnaces, where, combined 
with the fuel, it formed the gases of combustion. The greater heat thereby pro- 
duced was used to act upon the pistons and was then discharged. This machine 
avoided the defect of Ericsson's, in which the intense heat evolved acted as a 
destructive agent upon the machine itself. The heat "economizer" was also intro- 
duced. Through its medium the heat which is rejected by the fluid when it falls 
in temperature is saved and made to do work in conjunction with the direct 
power of the compressed air. A great difficulty has been the formation of ice in 
the pipes by the freezing of the water in the air; but this has been practically 
overcome. 

In work in mines, tunnels and confined situations, compressed air has 
demonstrated its great superiority over steam or any other power. Thus in the 
boring of the great Mt. Cenis tunnel, air was compressed by water power and 
carried in pipes to the heart of the mountain to work the boring machines. In 
that situation steam would have been intolerable, owing to its discharge in the 
confined space. The compressed air also possessed another immense advantage, 
namely, the ventilation and cooling of the tunnel. As the compressed air was 
discharged it expanded to the status of the surrounding air, and as it expanded 
it fell in temperature, thus cooling the surrounding air and causing ventilation. 

These earlier uses of compressed air were, however, only preparatory to the 
development of the power to-day. 

Who can deny that this power has a great future before it? Its forces are 
drawn from the inexhaustible storehouse of the atmosphere; its economy is 
expressed, in part, by the old phrase, "as cheap as air," 

Power and economy — the economy of power — is the great desideratum of 
industry and mechanics, the real philosopher's stone that will transmute all things 
to gold, and the chained energy of the air — chained to the perfected machine of 
this day of mechanicnl triumphs — is surely an ideal solution of the age-long 
problem. john j. rooney. 



12 PRODUCTION. 

COMPRESSED AIR PRODUCTION. 

Compressed air is air under pressure. It is usual to define compressed air 
as air increased in density by pressure, but we may produce compressed air by 
heat alone, as illustrated by the discharge of a cork from an empty bottle when 
heated. Though one of the oldest of the sciences, compressed air is, in its develop- 
ment and use, one of the youngest. Hero, of Alexandria, a century before Christ, 
experimented and wrote upon 'Pneumatics," calling special attention to the influ- 
ence of heat in expanding and contracting air. It is said that Hero put into 
practical use an invention by which the opening and closing of temple doors was 
effected by the alternate rarefaction and condensation of air which was brought 
in contact with heated and cooled surfaces of altar tops. Yet the science of 
pneumatics played no important part in industrial progress until scarcely more 
than a century ago it came into general use for diving bells, and was later on 
applied by Brunei to caisson work. 

In 1830 the French Academy of Sciences gave a medal to Thilorier for his 
method of compressing gases by stages. In 1849 the Baron von Rathen suggested 
the use of .compressed air at 750 pounds pressure per square inch in locomotives. 
It is a singular fact that the Baron, in describing the method by which he pro- 
posed to attain this high pressure, advised compound compressors with inter- 
coolers. The special advantages of cooling the air between the different stages 
of compression were set forth. This stage compression and inter-cooling is one 
of the most important recent improvements made in air-compressing machinery. 

Until recent years the use of compressed air in America has been confined 
almost exclusively to mining, tunneling, bridge-building, or to work in a confined 
space for which no other power was available. Electricity has recently become a 
competitor of compressed air in that it, too, may be used in confined spaces, and 
may be transmitted long distances and distributed. Until such competition arose 
the question of producing compressed air economically was but little agitated. 
The attention of engineers was mainly devoted to the development of an apparatus 
for using compressed air, it being taken for granted that air was an expensive 
power at best. The manufacturer sought to perfect his compressor on lines of 
low first cost, light weight, economy of space and general availability. Dry, pure 
air, delivered at a sufficient pressure by a machine which could be depended 
upon, has been the controlling consideration. 

Compressed air and air-compressing machinery have been considered, and 
the science developed by two classes of men — the practical men and the engineers. 
The practical men confined their work to the machine. The confusing diagrams 
and figures of the engineers were not considered, because they were not under- 
stood. The engineers took occasional plunges into compressed air theories, pro- 
ducing figures controverting certain well-established and so-called practical facts, 
and almost invariably basing the conditions of compressed air economy upon 
questions of thermodynamics. The problems produced by the engineers were too 
mathematical for the practical compressed air men. These men knew too little of 
the theory of compressed air, hence progress in the science has been slow. 

During recent years an impetus has been given to compressed air develop- 
ment by the strides made by electricity, and by the increased use of compressed aii 
in the arts. Electricity, although apparently a competitor, has really played the 



PRODUCTION. n 

part of a friend in pointing out the possibilities of transmission and use of air in 
[.directions before unknown ; thus a market has been created. 

The perfection of the air compressor on lines of economy naturally followed 
the wide use of compressed air in competition with steam and electricity. The 
best steam engine practice has been applied to the compressor. Compound con- 
densing Corliss engines are now used in connection with air cylinders of new 
design. 

The whole subject of compressed air may be divided into three heads: 

Production. 

Transmission. 

Use. 

No better evidence is needed of the obscurity of the science, even among 
engineers, than the fact that it is the usual thing to look upon compressed air as 
an expensive power, because of the great loss which is suffered during trans- 
mission. The great losses and the serious difficulties encountered in reality do 
not belong to transmission. Compressed air power may be transmitted and dis- 
tributed with no greater difficulty than the distribution and transmission of illumi- 
nating gas. It is a question of the size of pipe, volume and the pressure. There 
is not a properly designed compressed air installation in operation to-day that 
loses over five per cent, by the transmission alone. The question is altogether one 
of the size of pipe, and if the pipe is large enough the friction loss is a small item, 
is undoubtedly true that there are places where a conduit has been laid for a 
certain volume of air, and where the supply has been increased without increasing 
the size of the conduit, the result of this being that more air is forced through 
the pipe than its sectional diameter will admit economically ; hence the velocity 
of flow is increased, and as the friction is in direct proportion to the velocity the 
loss of power is also increased. The largest compressed air long-distance power 
plant in America^ is that at the Chapin Mines in Michigan, where the power is 
generated at Quinnesec Falls, and transmitted three miles. This is not an 
economical plant, but the loss of pressure, as shown by the gauge, is only two 
pounds, and this is the loss which may be laid strictly to transmission. During 
the construction of the Jeddo Tunnel, near Hazelton, Pa., compressed air at 60 
pounds pressure was conveyed 10,860 feet from the central station. The writer 
was called upon to explain a mysterious condition which existed on both ends of 
the line. The pressure gauge recorded the same figures and the gauges were sent 
to the shops for repairs, because everybody was convinced that "something was 
wrong." The result was not changed when the gauges had been "repaired," it 
being evident that this apparently perfect economy of transmission was due to the 
fact that a large pipe (nearly six inches in diameter) was used at that time to 
convey so small a volume of air that the velocity in the pipe produced so small a 
friction loss that it could not be recorded on the gauge. 

Having defined compressed air we must next define heat, for in dealing 
with compressed air we are brought face to face with the complex laws of Ther- 
modynamics. When we produce compressed air we produce heat, and when we 
use compressed air as a power we produce cold. Based on the material theory of 
heat, it was said that when we take a certain volume of free air and compress it 
into a smaller space we get an increase of temperature, because we have the 
heat of the original volume occupying less space ; but no one at this date accepts 



14 PRODUCTION. 

the material theory of heat. The science of Thermodynamics teaches that heat 
and mechanical energy are only different phases of the same thing, the one being 
the motion of molecules and the other that of masses. This is the accepted 
theory of heat. In other words, we do not believe that there is any such thing 
as heat, but that what we call heat is only the sensible effect of motion. In the 
cylinder of an air compressor the energy of the piston is converted in molecular 
motion in the air, and the result or the equivalent is heat. A higher temperature 
means an increased speed of vibration, and the lower temperature means that this 
speed of vibration is reduced. If we hold an open cylinder in one hand and a 
piston in the other, and place the piston within the cylinder, we here have a con- 
fined volume of air at normal temperature and pressure. These particles of air 
are in motion and produce heat and pressure in proportion to that motion. Now. 
if we press the piston to a point in the center of the cylinder, that is, to one-half 
the stroke, we here decrease the distance between the cylinder head and the pis- 
ton just one-half; hence each molecule of air strikes twice as many blows upon 
the piston and head in traveling the same distance, and the pressure is doubled. 
We have also produced heat (about ii6 degrees), because we have expended a 
certain amount of work upon the air ; the air has done no work in return, but we 
have increased the energy of molecular vibration in the air, and the result 
is heat. 

But what of this heat? What harm does it do? If we instantly release 
the piston which we have forced to one-half stroke, it will return to its original 
position less only a fractional part, due to friction. We have, therefore, recovered 
all or nearly all the power spent in compressing the air. We have simply pressed 
and released a spring, and this illustration shows what a perfect spring com- 
pressed air is. We see also the possibility of expending one horse-power of 
energy upon air and getting almost one horse-power in return. Such would be 
the case in practical work if we could use the compressed air power immediately 
and at the point where the compression took place. This is scarcely possible, as 
the heat in the air is soon lost by radiation, and we have lost power. 

Thirteen cubic feet of free air at normal temperature and barometric pres- 
sure weigh about I pound. In the illustration referred to about ii6 degrees of 
heat are liberated at half stroke of a compressor. The gauge pressure at this point 
reaches 24 pounds. According to Mariotte's law, "the temperature remaining con- 
stant, the volume varies inversely as the pressure," we should have 15 pounds 
gauge pressure at half stroke. The difference, 9 pounds, represents the effect of 
the heat of compression in increasing the relative volume of the air. 

The specific heat of air under constant pressure being 0.238, we have 
0.238 X 116 = 27.6 heat units produced by compressing one pound, or 13 cubic 
feet, of free air into one-half its volume; 27.6 X 772 (Joule's equivalent) =21,307 
foot pounds. We know that 33,000 foot pounds is one horse-power, and we see 
how easily about two-thirds of a horse-power in heat units may be produced and 
lost in compressing one pound of air. Exactly this same loss is suffered when 
compressed air does work in an engine without reheating, and is expanded down 
to its original pressure. In other words, the heat of compression and the cold of 
expansion are in degree equal. 

Figure i is a sketch designed to indicate graphically the effect of heat and 
cold in compression and expansion of air. 



PRODUCTION. 



15 



the sketch illustrates an open cylinder, which may serve both as an air 
compressor and an air engine. The piston at the point shown is supposed to 
confine a volume of free air in the cylinder and at a temperature of 60 degrees ; 
let it be pressed down until it reaches the point indicated by 45 pounds, and the 
pressure will follow the dotted lines marked "Adiabatic." This is, of course, as- 
suming that the heat, which is invariably produced by compression, is suffered to 
remain in the air and to influence the pressure. We here have a confined volume 
of compressed air at a pressure of 45 pounds and a temperature of 320 degrees. 
Let there be no absorption of heat and the piston if released will return to the 
starting .point, the pressure following exactly the line indicated during com- 
pression and the temperature returning to 60 degrees. In such a case we assume, 
of course, that^the piston is frictionless. This points to the fact that com- 




.g>»\.<Si>»-X.vt i»L|i»t\»v»'rv » I 
e- » ii n ^ a- 

FIG. I. 



O VSoWe V wvoV. >Tt4.SUTe4. 



POAtCtv oV ItTOV) 



pressed air is a perfect spring, and that the heat of compression when utilized 
can be made to return its full value of energy. 

An Air Compressor provided with no cooling device would show a pres- 
sure line following closely that marked "Adiabatic" on Fig. i. The hot com- 
pressed air confined in the cylinder at the 45-pound point, if transferred through 
pipes to an air engine and maintained hot until used, would be available for 
work in the sam.e proportion (less a little friction) as we have shown in the 
theoretical case where the piston, used as a compressor, is driven back to the 
starting point. Practically, it is impossible to convey hot compressed air any 
distance from the compressor, for air, though very slow in taking up heat, has 
so low a specific heat that it parts with its temperature rapidly. Steam having 
a higher specific heat may be conveyed as a power even through naked pipes, and 
this fact has led to mistakes in regard to the possibilities with compressed air. 

Returning to Fig. i, let us imagine that the piston has been stopped at the 
45-pound point, and that the compressed air, which, as we have seen, has a tern- 



i6 



PRODUCTION. 



perature of 320 degrees, is transferred into a receiver and used at a point say half 
a mile distant. The temperature will now be reduced to that of the surrounding 
medium, or to the initial temperature, which the sketch shows to be 60 degrees; 
and if the system is well designed, that is, if the pipes are large enough and there 
are no leaks or other irregularities, we will have nearly 45 pounds pressure on 
the other end of the line, as there is a direct elastic medium between the two 
points. But the volume will be reduced in size, because of the reduced tempera- 
ture, and will correspond with the space underneath the lowest dotted line in the 
figure marked "Volume I." If it is now used "without reheating to do work in 
an engine, the line of reduction in pressure will follow the lower dotted line 
marked "Adiabatic" until it reaches the point marked 201 degrees, which repre- 

Table I. — Of the volume and weight of dry air at different temperatures 

UNDER A CONSTANT ATMOSPHERIC PRESSURE OF 29.92 INCHES OF MERCURY IN 
THE BAROMETER (ONE ATMOSPHERE), THE VOLUME AT 32° FAHRENHEIT BEING I. 



3 tfl 


•^ "dl 




a 

s 


.S ti 


.0 


s 


•5 ti 









"^ 


<-> U5 


"H D 


■- 


4-> in 


— 1) 


•'" 


pera 

in 
gree 




II 


2 a S! 


IS 


|l 


S a 5i 




II 


1 ' 


If 


V 


1 ' 


II 


V 


a V 

1 ' 


II 




32 


1-000 


0-0807 


275 


1-495 


0-0540 


1,300 


3-585 


0-0285 


42 


l-()20 


0791 


300 


1-546 


0-0522 


1,400 


3-789 


0218 


52 


1-041 


0-0776 


325 


1-597 


0-0506 


1,500 


3-993 


0-0202 


62 


1-061 


0-0761 


350 


1-648 


0-0490 


1,600 


4-197 


0-0192 


72 


1082 


0-0747 


375 


1-689 


0-0477 


1,700 


4-401 


0-0183 


82 


1-102 


0-0733 


400 


1-750 


0-0461 


1.800 


4-605 


0-0175 


92 


1122 


0-0720 


450 


1-852 


0-0436 


1,900 


4-809 


0-0168 


102 


1-143 


0-0707 


500 


1-954 


0.0413 


2,000 


5-012 


0-0161 


112 


1-163 


0694 


550 


2 056 


0-0384 


2,100 


5-216 


0-0155 


122 


1-184 


0-0682 


6C0 


2-158 


0-0376 


2,200 


5-420 


0149 


132 


1-204 


0-0671 


650 


2-260 


0-0357 


2,300 


5-624 


0142 


142 


1-224 


0-0660 


700 


2-362 


0-03:^8 


2,400 


5-828 


0-0138 


152 


1-245 


0-0649 


750 


2-464 


0328 


2,500 


6-032 


0-0133 


162 


1-265 


0-0638 


800 


2-566 


0-0315 


2,K00 


6-236 


0130 


172 


1-285 


0-0628 


850 


2-668 


0303 


2,700 


6-440 


0-0125 


182 


1-306 


0-0618 


SOO 


2-770 


0-0292 


2.800 


6-644 


0121 


192 


1-326 


0-0600 


950 


2-872 


0-0281 


2,900 


6-847 


0-0118 


202 


1-347 


00600 


1,000 


2-974 


0-0-268 


3,000 


7-051 


0-0114 


212 


1-367 


0-0591 


i.ino 


3-177 


0-0254 


3,100 


7-255 


0111 


230 


1-404 


00575 


1,200 


3-381 


0-02.39 


3,200 


7-459 


0-0108 


250 


1-444 


00559 















sents the theoretical temperature of the air when exhausted at atmospheric pres- 
sure. We now see that the piston, instead of returning to the starting point, has 
only had power enough behind it to return it to a point about half way. 

The illustration points to the importance in compressed air economy of re- 
ducing to the lowest point practicable the temperature of the air before and dur- 
ing compression and conversely increasing to the highest point the temperature 
before and during use or expansion. 

If, in the case referred to, heat had been applied during expansion, the 
pressure would follow the line marked "Isothermal Expansion," and the piston 
might be returned to the starting point. 



PRODUCTION. 



Another case is shown by the sketch in which the air is compressed adia- 
batically to 45 pounds pressure and heat enough is applied during expansion to 
maintain the temperature at 520 degrees until the air is exhausted at atmos- 
pheric pressure. This case is purely theoretical and illustrates the possibility of 
obtaining more power out of a given volume of air after compression than was 
expended at the compressor. 

Experiments made by M. Regnault and others on the influence of heat 
on pressures and volumes of gases have enabled us to fix the absolute zero of 
temperature as about -461 degrees Fahrenheit. This point, — 461 degrees below 
zero, has been taken to be the theoretical point at which a volume of air is re- 
duced to nothing. The exact figures representing absolute zero vary with dif- 
ferent authors, but for all practical purposes -461 degrees F. is near enough. The 
volume of air at different temperatures is in proportion to the absolute tempera- 
lure, and on this basis Box has produced Table i. 

The effect of the heat of compression in increasing the volume, and the 
heat produced at different stages of compression, are shown by Table 2 (Box) : 

A cubic foot of free air at a pressure of one atmosphere (equal to 14.7 

Table 2. — Heat produced by compression of air. 





Pressure. 




1 













)erature of 
he Air 
Ighout the 
5. Degrees 


. 






Pounds per 




1 


Pounds per 


Sq. Inch 


.5 tJ 


SS^ 




Sq. Inch 


above the 


3 

> 


5 a^ 


< 


above a 
Vacuum. 


Atm'sph're 
(Gauge 


1 5g 








Pressure). 




PL. 




100 


14-70 


0-00 


1-0000 


60-0 


00-0 


110 


16-17 


1-47 


0-9346 


74-6 


14-e 


1-25 


18-37 


3-67 


8536 


94-8 


34-8 


1-50 


22-05 


7-35 


0-7501 


124-9 


64-9 


1-75 


25-81 


11-11 


0-6724 


151-6 


91-6 


2-00 


29 40 


14-70 


0-6117 


175-8 


115-8 


2-50 


36-70 


22-00 


0-5221 


218-3 


158-3 


3 00 


44-10 


29-40 


0-4588 


255-1 


195-1 


3-50 


51-40 


36-70 


0-4113 


297-8 


227-8 


400 


58-80 


44-10 


0-3741 


317-4 


257-4 


.5-00 


73-50 


58-80 


3194 


3694 


309 4 


6 00 


88-20 


73-50 


0-2806 


414-5 


354-5 


7-00 


102 90 


88-20 


0-2516 


454-5 


394-5 


8-oa 


117-60 


102-90 


0-2288 


490-6 


430-6 


9-00 


13-2-30 


117-60 


0.2105 


523-7 


468-4 


1000 


147-00 


132-30 


01953 


5540 


494-0 


15-00 


220-50 


205-80 


0-1465 


681 


6210 


2000 


294-00 


279-30 


0-1195 


781-0 


721-0 


25-00 


367-50 


352-80 


0-1020 


864-0 


804-0 



pounds above a vacuum) at a temperature of 60 degrees, when compressed lo 
twenty-five atmospheres, will register 367.5 pounds above a vacuum (352.S 
pounds gauge pressure) will occupy a volume of 0.1020 cubic foot, will have a 
temperature of 864 degrees, and the total increase of temperature is 804 degrees. 
These tables apply to dry air only. The effect of moisture will vary the 
figures of temperature, and to some extent will affect the pressures, but many 
useful deductions may be drawn from the tables. It is seen for instance by 



i8 PRODUCTION. 

studying table i that a volume of dry air will be doubled if its temperature is in- 
creased about SCO degrees, and conversely, of course, if the volume remains con- 
stant an increase of about 500 degrees in temperature will double the pressure. 
The addition of moisture serves to increase these figures, because moisture in- 
creases both the specific heat and the heat conducting capacity of the air. 

The thermal results of air compression and expansion are shown by the 
accompanying diagram (Fig. 2). Both the temperature of the air and its volume 
are shown at different stages of compression. The simplest application of this 
diagram is tliat which gives the gauge pressure represented at different points of 
the stroke. This is shown in the vertical lines. But in compressing air we pro- 
duce heat, and it is important to know the temperature at any given pressure, also 
the relative volume. A.11 of these are shown in the diagram. The initial volume 
of air equal to i is taken and divided into ten equal parts. Each division between 
two horizontal lines, shown by the figures at the right, representing one-tenth 
of the original volume. 

The vertical and horizontal lines are the measures of volumes, pressures 
and temperatures. The figures at the top indicate pressures in atmospheres above 
a vacuum; the corresponding figures at the bottom denote pressures by the gauge. 
At the right arc volumes from one-tenth to one. At the left are degrees of tem- 
peratures from zero to 1,000 degrees Fahrenheit. The two curves which begin at 
the upper left hand corner and extend to the lower right are the lines 
of compression. 

The upper one being the "Adiabatic" curve, or- that which represents the 
pressure at any point on the stroke with the heat developed by compression re- 
maining in the air; the lower is the "Isothermal," or the pressure curve unin- 
fluenced by heat. The three curves which begin at the lower left hand corner and 
rise to the right, are heat curves and represent the increase of temperature corre- 
sponding wath different pressures and volumes, assuming in one case that the tem- 
perature of the air before admission to the compressor is zero, in another sixty 
degrees, and in another one hundred degrees. 

Beginning with the adiabatic curve, we find that for one volume of air, 
when compressed without cooling, the curve intersects the first vertical line at a 
point between 0.6 and 0.7 volume, the gauge pressure being 14.7 pounds. If we 
assume that this air w^as admitted to the compressor at a temperature of zero, it 
will reach about 100 degrees when the gauge pressure is 14.7 pounds. We find 
this by following down the first line intersected by the adiabatic curve to the 
point where the zero heat curve intersects the same line, the reading being given 
in figures to the left immediately opposite. If the air had been admitted to the 
compressor at 60 degrees, it would register about 176 degrees at 14.7 pounds 
gauge pressure. If the air were 100 degrees before compression, it would go up 
to about 230 degrees at this pressure. Following this adiabatic curve until it 
intersects line No. 5, representing a pressure of five atmospheres above a vacuum 
(58.8 lb. gauge pressure) we see that the total increase of temperature on the 
zero heat curve is about 270 degrees ; for the 60 degree curve it is about 370 de- 
grees, and for the 100 degree curve it is about 435 degrees. The diagram shows 
that when a volume of air is compressed adiabatically to 21 atmospheres (294 
lb. gauge pressure) it will occupy a volume a little more than one-tenth; the 



PRODUCTION. 



19 



total increase of temperature with an initial temperature of zero is about 650 
degrees; with 60 degrees initial temperature it is 800 degrees, and with 100 de- 
grees initial it is 900 degrees. It will be observed that the zero heat curve is 
flatter than the others, indicating that when free air is admitted to a compressor 
cold, the relative increase of temperature is less than when the air is hot. This 
points to the importance of low initial temperature. It is plain that a high initial 
temperature means a higher temperature throughout the stroke of a compressor. 
The diagram gives the loss of temperature during compression from initial tem- 
peratures of deg., 60 deg., 100 deg. If we compare the compression line from 
zero with the compression line from 100 deg., we observe that in compressing 
the air from, say i atmosphere to 10 atmospheres, the original difference, which 




Fig. 2. 



at the start was only 100 deg., has now been about doubled; that is, it has reached 
200 deg., and in carrying the compression to 20 atmospheres the difference now 
becomes about 250 deg. Each horizontal division represented by the figures at 
the left is equal to 100 deg., and the space between any two adjacent horizontal 
lines may be subdivided into 100 equal parts representing i deg. each. 

Where there is a sy.slem of cooling the air during compression, the lines 
on the indicator cards can be traced between the adiabatic and isothermal curves 
on the diagram., In practice the best compressors show a line about midway be- 
tween these two curves. Compressors using a .'^pray of water for cooling show a 
pressure line a little nearer the isothermal, but for reasons which will be referred 
to later on, spray compressors are now but little used. 

For all practicr.1 purposes in using this diagram it is best to follow the 
adiabatic curve in all determinations, except where the exact pressure line is 
known. This diagram will be found convenient to those who are called upon to 
figure the pressure at different points m the stroke of an air compressor, and it 
points oul tlic common error of neglecting to take into consideration in oue",s 



20 



PRODUCTION. 



figures the fact that, at the beginning of the stroke, one atmosphere in volume 
already exists. Beginning at the upper left hand corner, the adiabatic pressure 
curve intersects the first vertical line at that point in the stroke when the pressure 
on the gauge will register 14.7 pounds. 

The next vertical line shows where the gauge reaches 29.4 pounds, and it is 
evident here that the piston of an air compressor travels much farther in reaching 
14.7 pounds than in doubling that pressure or in reaching 29.4 pounds; thus an 
air compressor is an engine of unevenly distributed resistance. During the early 
stages of the stroke it has a slowly accumulating loal to carry, while later on this 






i"^^ oiAvTaiiCuVvch, 






ATn\osj>'\\.ev\c LHtl* 




.r46l°^l>.6olute.2rerp_. , I. ^ ^^^ J 

WoyK b^ J\ <V.v ivl} <xT'-\."c. Co TTvy -t e 66-v<s n. , 
;,« ?re&si;-»e. iB. To ioo^» Ciwg^e Press utc. 



A. Tc \5^^«&^ 



C F»or(v\5 



{^o^>r>"Vv of lA c\\, <sl\><vXv »^ t,)Lp <Xtv^t VjO -vv 



Cja.\)a<t. Vy e«,fevTe. 



-57'+6o'«ll7«xifcV= 21,469 Ft.Mt. 



10. fTom. ioo'V"»»s. cfAuAe PTessvre 



E. -4-Gi°-g7''»4.o»''xiS3.'a 74-,1^4-' rt Wt T- -46l''-S64.°«97">Cl85.^, < 7,799 Ft.PAa. 
Tot*l Can4 E. e5 60i Ft. PA*„ TotrtX D.onA F. «5,^oa Ft. Pia. 

Fig. 3. 

load is multiplied very rapidly. This is one of the reasons for heavy fly wheels 
in air compressors. 

Figui-e 3 is a graphic diagram drawn for the purpose of illustrating the 
fact that the power which is contained in any volume of air at a given pressure 
rs dependent upon its distance in temperature above the absolute zero, and that 
there is as much power in a pound of air at fifteen pounds gauge pressure and 60 
degrees temperature as there is in one pound of air at 100 pounds gauge pressure 
and 60 degrees temperature. Orre pound, or thirteen cubic feet of air at fifteen 
pounds pr-essure and 60 degrees temper-ature, is represented by the space C. The 
available power in this air is 21,469 foot pounds. By available power is meant 
the amount of power which can be irtilizcd when this air is expanded adiabatically 
to atmospheric pressure. The diagram shows that when such pressure is reached 
the tempei-aturc will be— 57 degrees Fahr. There still remains in this air a cer- 



PRODUCTION. 21 

tain amount of intrinsic energy, and the diagrani and figures show that this 
energy is equal to 74,134 foot pounds. This added to the available energy gives 
us 95,603 foot pounds, as the whole energy contained in one pound of air at fif- 
teen pounds pressure and 60 degrees temperature. 

D represents one pound of air at 100 pounds pressure and 60 degrees tem- 
perature. Its available energy is 77,804 foot-pounds, and its intrinsic energy is 
17,799 foot-pounds, or the total energy is 95,603 foot-pounds, which is exactly 
equal to the case just cited. 

These figures show the correctness of that thermodynamic law, which 
states that the power of any elastic gas is in direct proportion to its height of 
fall. So long as the temperature is above the absolute zero, there is as much 
power in the same body of air when expanded adiabatically from a moderate tem- 
perature to an extremely low one, as when expanded from a high temperature 
to a moderate one, and this offers to some extent a limitation to that system of 
reheating which increases the volume without at the same time increasing the 
pressure. 

The development of heat when air is compressed is, perhaps, the best 
illustration of the acknowledged thermodynamic principle that work and heat 
are interchangeable unit for unit. When air is compressed all the work done 
in compression is converted into heat. This heat is capable of being converted 
back again into power. But the question is frequently asked, if it be true that the 
power applied in the steam cylinder of an air compressor is all converted into 
heat in the air cylinder, how is it that power still remains in the compressed air 
after the heat has been lost through transmission? 

In order to get a clear understanding of this, we must know that air is a 
power in itself before compression ; that it contains a certain capacity for work 
due to its elasticity. It is not, however, in a condition available for work until 
compressed. This energy is made available by giving it a height of fall which 
is represented by a difference in pressure between the compressed air on one side 
and the free air on the other. 

If we box up free air at any given temperature and under normal atmos- 
pheric conditions, we have within the enclosure a well defined amount of energy. 
We cannot use it to perform work unless the pressure outside is less than that 
inside the enclosure. This may be accomplished by placing the closed vessel in 
the rarified atmosphere, such as exists at altitudes, but in any case, there is a well 
defined quantity of intrinsic energy within the air itself, the limit being meas- 
ured by the height of fall between the free air in the vessel and absolute zero. 

Compression as now practiced only serves the purpose of placing the 
natural power which we have in the air, into a condition which makes it possible 
for us to utilize it. This points to an undeveloped science in the use of com- 
pressed air. Inasmuch as we lose all the power expended in compression and yet 
have a capacity for useful work equal to from 30 to 50 per cent, of that power, 
it is plain that there arc possibilities in the science which are now misunderstood 
and not realized. 

It is theoretically possible to realize out of compressed air more power 
than was expended at the compressor. This has been shown in Fig. i, but that 



22 PRODUCTION. 

this statement might not be confused with perpetual motion theories, the sketch 
shown in Fig. 4 has been prepared. 

Sulphuric acid in its concentrated form will, when exposed in an open dish 
absorb moisture from the atmosphere to the extent of about double its weight. 
A hypothetical assumption is made of a pump arranged to discharge sulphuric 
acid in the direction shown by the arrow to an open dish, elevated (say) 100 feet. 

The amount of power necessary to discharge a certain quantity of sul- 
phuric acid into this dish is exactly equal to the power which the sulphuric acid 
is capable of giving out when falling back again, less the friction of the pump, 
leakage, etc. Now, let us assume that the sulphuric acid in the open dish re- 
mained there long enough to absorb moisture from the atmosphere until its 
weight has been doubled ; it will thus obviously have twice the amount of power 







Fig. 4. 



in falling back again, and if the friction and leakage losses were not too great, 
it will be capable of driving the pump and of returning an equivalent volume of 
the concentrated acid to the dish. If the same acid is used over again, the 
moisture must be driven out, and lamps are shown in the sketch provided for this 
purpose. The analogy between this hypothetical case of sulphuric acid and one 
of compressed air is, that, as with acid we may draw power from moisture which 
is contained in the air, so with compressed air may we draw upon the intrinsic 
heat energy of the atmosphere. 

If it were practicable to compress air isothermally — that is, without heat — 
we might illustrate the point referred to in the foregoing by placing an air com- 
pressor in a cold room, or what M'ould amount to the same thing, taking in cold 
air to the cylinder of the compressor, this air being taken, for instance, from a 
cold storage room, and on being compressed the temperature being maintained 



PRODUCTION. 23 

at the initial point. This cold compressed air might then be led in pipes, placed 
on the surface of the ground and exposed, say, to the hot sun, so that when used 
its temperature might be largely mcreased above that at the compressor. 

We would here have a case of reheating by natural conditions, and the 
possibility of obtaining more power at the motor than was expended at the com- 
pressor is made apparent. 

All this appears to be but theory, yet the value of the argument lies in the 
fact that it points to what may be accomplished in the future and to the impor- 
tance at present of low initial temperature at the compressor and high temperature 
at the motor. It is a common thing to see air compressors at work in engine 
rooms drawing the air into the cylinder at the temperature of the engine room, 
which, in many instances, especially in winter, is 50 degrees higher in temperature 
than that of the air on the outside. Even where air compressors are used with 
concentrated inlets made for the express purpose of being connected with the 
atmosphere from the outside, this question of economy by low initial temperature 
i:, frequently neglected. For every 5 degrees by which the initial temperature of 
the intake air is lowered, there is a gain of one per cent, in volume. 

It is not a difficult matter to construct an air compressor plant where the 
intake air is made to pass over refrigeration pipes. In cities where ice-making 
plants are in operation, the best point to place the air compressor is alongside the 
ice-making machines, the combination of the two industries being advisable. 

On the other end of the line reheating is of great importance. A perfect 
reheater has not yet been found, though at this time reheaters are in use which 
give practical results. It has already been demonstrated that compressed air may 
be increased in temperature and thus proportionately increased in volume and 
efficiency by the application of heat in a very economical manner, the quantity of 
coal consumed in proportion to the gain in economy being very small. 

Mr. Robert Hardie, in his experiments with a pneumatic motor using a hot 
water reheater, has figured the cost of reheating at one-eighth the coal required at 
the compressor. Professor Haupt, referring to this heater, makes the following 
statement : 

"The power required to compress 1,000 cubic feet of free air to 2,000 pounds 
per minute would be 400 horse-power, consuming 1,200 pounds of coal per hour at 
a cost of $1.80 (at $3 per ton), and the cost of reheating would not exceed 22 
cents to double the work performed. That these statements are not simply theo- 
retical deductions have been proved by actual tests. The Rome air motor when 
using a reheater ran fourteen miles on a consumption of 308 cubic feet of free air 
per mile. When the air was not reheated, the consumption of air per mile was 
661 cubic feet." 

The first loss in air compression, that due to the fact that the heat produced 
cannot be maintained, is an unavoidable loss. The second loss may be called the 
influence of the heat of compression, and is due to the fact that this heat increases 
the relative volume of the air and resists compression. This heat of compression 
has long been the bete noire of air compressor builders. At first it seriously af- 
fected the valves and packing, and this served as an argument in favor of injecting 
water into the cylinder, the claim of manufacturers being that by keeping down 
the heat of compression repairs would be less and accidents due to the destruction 
of parts by heat would be avoided. 



24 PRODUCTION. 

The injection of water into the air cylinder is usually known as the Col- 
ladon idea. Compressors built on this system have shown the highest isothermal 
results. It is plain that the injection of cold water in the shape of a finely divided 
spray directly into the air during compression will lower the temperature to a 
greater degree than to simply surround the cylinder and parts by water jackets. 

Two systems are in use by which it is attempted to absorb the heat during 
compression. These systems divide air compressors into two classes — 

(i) Wet compressors. 

(2) Dry compressors. 

A wet compressor is one which introduces water directly into the cylinder 
during compression. 

A dry compressor is one which admits no water to the air during com- 
pression. 

Wet compressors may be subdivided into two classes — 

(i) Those which inject water in the form of a spray into the cylinder 
during compression. 

(2) Those which use a water piston for forcing the air into confinement. 

The advantages of water injection during compression are as follows: 

(i) Low temperature of air during compression, hence a reduced mean 
resistance and a saving of power. 

(2) Increased volume of air per stroke, due to filling of clearance spaces 
with water, and to a cold air cylinder. 

(3) Low temperature of air immediately after compression, thus con- 
densing moisture at the air receiver. 

(4) Low temperature of cylinder and valves, thus maintaining packing, etc. 

(5) Economical results due to compression of moist air. (See Table No. 4.) 
The first advantage is by far the most important one, and is really the only 

excuse for water injection in air compression. 

The percentage of work of compression (dry air) which is converted into 
heat and lost when no cooling system is used is as follows : 

Compressing to 2 atmospheres, loss 9.2 per cent. 
" 3 " " 15.0 " " 

" 4 " " 19.6 " " 

" 5 " " 21.3 " " 

" 6 " " 24.0 " " 

"8 " " 27.4 " " 

We see that in compressing air to five atmospheres, which is the usual 
practice, the heat loss is 21.3 per cent., so that if we keep down the temperature of 
the air during compression to the isothermal line, we save this loss. The best 
practice in America has brought this heat loss down to 3.6 per cent, (old Inger- 
soll Injection Air Compressors), while in Europe the heat loss has been reduced 
to 1.6 per cent. Steam-driven air compressors are usually run at a piston speed 
of about 350 feet per minute, or from 60 to 80 revolutions per minute of com- 
pressors of average sizes, say 18 inches diameter of cylinder. Sixty revolutions 
per minute is equal to 120 strokes, or two strokes per second. An air cylinder 18 
inches in diameter filled with free air once every half second, and at each stroke 
compressing the air to 60 pounds, and thereby producing 309 degrees of heat, is 



PRODUCTION. 



25 



thus by means of water injection cooled to an extent hardly possible with mere 
surface contact. The specific heat of water being about four times that of air, it 
readily takes up the heat of compression. 

A properly designed spray system must not be confused with the numerous 
devices applied to air cylinders by means of which water is introduced. In some 
cases the water is merely drawn in through the inlet valves. In others it passes 
through the centre of the piston and rod, coming in contact with the interior walls 
of the air cylinder between the packing rings. Introducing water into the air 
cylinder in any other way, except in the form of a spray, has but little effect in 
cooling the air during compression. On the contrary, it is a most fallacious sys- 
tem, because it introduces all the disadvantages of water injection without its 
isothermal influence. Water, by mere surface contact with air, takes up but little 
heat, while the air having a chance to increase its temperature, absorbs water 
through the affinity of air for moisture, and thus carries over a volume of satu- 
rated hot air into the receiver and pipes, which on cooling (as it always does in 
transit to the mine), deposits its moisture and gives trouble through water and 
freezing. It is therefore of much importance to bear in mind that unless water 
can be introduced during compression to such an extent as to keep down the tem- 
perature of the air in the cylinder, it had better not be introduced at all. 

If too little water is introduced into an air cylinder during compression, 
the result is warm, moist air, and if too much water is used it results in a surplus 
of power required to move a body of water which renders no useful service. 

The following Table 3 deduced from Zahner's formula gives the quantity of 
water which should be injected per cubic foot of air compressed in order to keep 
the temperature down to 104° F. : 

Table 3. 





Weight of water to 


Weight of water to 




be injected at 


be injected at 


Compression by 


68'^ Fah. to keep the 


68" Fah. to keep the 


atmosphere above 


temperature at 


temperature at 


a vacuum. 


104° Fah. in lbs. of 


104» Fah. in lbs. 




water and per 


of water for 




lbs. of free air. 


1 cu. ft. of free air. 


2 


0-734 


0-056 


3 


1-664 


0-089 


4 


1-469 


0113 


5 


1-701 


0131 


6 


1-891 


0-145 


7 


2-063 


0-158 


8 


2-204 


0-167 


9 


2-329 


0-179 


10 


2-440 


0-188 


11 


2-542 


0195 


12 


2-634 


0-202 


13 


2-719 


0-209 


14 


2-798 


215 


15 


2.871 


0-223 



Experiments were made under the personal supervision of Prof. Denton 
rat the Stevens Institute of Technology, to determine the relative effects in air 
[compressors of water injection and water jackets. An extended controversy 
I had been carried on in the "Engineering and Mining Journal" between the writer 



26 



PRODUCTION. 



and others upon the question whether or not the injection of water reduced the 
temperature and increased the efficiency. It was claimed by some that the 
efficient indicator cards taken from certain injection compressors were not 
reliable because of leakage. It was only on such grounds that the proximity of 




Fig. 5. 



the pressure line to the isothermal could be explained away. In the Stevens 
Institute tests the greatest care was exercised to secure air-tight pistons and 
valves, and as these experiments were unbiased and in the hands of experts, the 
results may be accepted as conclusive so far as indicating isothermal economy 
by an efficient system of injection. Fig. 5 herewith represents graphically the 
results obtained at the Stevens Institute.* No clearance is shown, because the 
purpose of the illustration is to show the comparative effect of the various 
methods of cooling. The air was compressed to 150 pounds gauge pressure, the 



*Frorn a paper by Mr. R. A. Parke. 



PRODUCTION. 



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28 PRODUCTION. 

work done in each case being represented by the area between the pressure curve 
and the rectangular lines. 

The pressure curve is determined in each case by the formula — 

Pi \V / 

In the case of isothermal compression (assuming no heat produced), the 
exponent N=i. In adiabatic compression (the full effect of the heat of com- 
pression being available), N^i.408. It is obvious that the value of the exponent 
N will vary between the two points i, and 1.408. From a large number of in- 
dicator cards taken at the Stevens Institute the following values were shown : 

Water jacket N=i.35 

Water jet injection N=i. 33 

Water spray injection N=i.25 

It has been demonstrated by experiments made in France that the power re- 
quired to compress dry air has been prepared from the data of M. Mallard, and 
shows that for five atmospheres the work expended in compressing one pound 
of dry air is 58,500 foot pounds, while that for moist air is 52,500 foot pounds. In 
expansion also moisture in the air adds to the economy, but in both cases the 
saving of power is not great enough to compensate for the many disadvantages 
due to the presence of water. Mr. Norman Selfe, of the Engineering Associa- 
tion of N. S. W., has compiled a table which -shows some important theoretical 
conditions involved in producing compressed air. 

There are many serious objections, however, to the use of water within the 
air cylinder. These objections are so serious that it has been found to be the 
best practice to suffer the heat loss during compression, and thus simplify the 
apparatus. Some of the objections may be stated as follows : 

1. The mechanical difficulties involved in introducing the water into the 
cylinder so intimately mixed with the air during compression as to reduce the 
temperature of compression immediately when produced. 

2. Impurities in the w^ater, which, through both mechanical and chemical 
action, destroy exposed metallic surfaces. 

3. Wear of cylinder, piston and other parts, due directly to the fact that 
water is a bad lubricant; and as the density of water is greater than that of oil, 
the latter floats on the water and has no chance to lubricate the moving parts. 

4. Wet air arising from insufficient quantity of water and from inefficient 
means of ejection. 

5. Mechanical complications connected with the water pump, and the dif- 
ficulties m the way of proportioning the volume of water and its temperature to 
the volume, temperature and pressure of the air. 

6. Loss of power required to overcome the inertia of the water. 

7. Limitations to the speed of the compressor, because of the liability to 
break the cylinder head joint by water confined in the clearance spaces. 

8. /\bsorption of air by water. 

Before the introduction of condensing air receivers, wet air resulting in 
freezing was considered the most serious obstacle to water injection; but this 



PRODUCTION. 29 

ifficulty no longer exists, as experience has demonstrated that a large part of 
le moisture in compressed air may be abstracted in the air receiver. Even in 
le so-called dry compressors a great deal of moisture is carried over with the 
)mpressed air, because the atmosphere is never free from moisture. This sub- 
let will be referred to more fully when treating of the transmission of com- 
pressed air. 

A serious obstacle to water injection, and that which condemns the wet com- 
pressor, is the influence of the injected water upon the air cylinder and parts. 
Even when pure water is used, the cylinders wear to such an extent as to pro- 
duce leakage and to require reboring. The limitation to the speed of a com- 
pressor is also an important objection. The claim made by some that the injected 
water does not fill the clearance spaces, but is aerated, does not hold good, ex- 
cept with an inefficient injection system. 

Whether it be water or spray which occupies the clearance space, it is 
impossible for air and spray to occupy the same place at the same time. " 

The writer has increased the speed of an air compressor (cylinders 12 in. 
and 12 in. by 18 in., injection) ten revolutions per minute by placing his fingers 
over the orifice of the suction pipe of the water pump. The boiler pressure re- 
mained the same, the cut-off was not changed and the air pressure was uniform, 
hence this increase of speed arose from the fact that the water was restricted 
and the clearance spaces were filled with compressed air, which served as a 
cushion or spring. While the volume of compressed air furnished by this com- 
pressor would be somewhat reduced by the restriction of the water, yet the in- 
crease in speed which was obtained without any increase of power, fully com- 
pensated for the clearance loss. 

Unless the water of injection can be used efficiently as a cooling agent, its 
value for clearance does not compensate for the disadvantages attending its use. 
Tn some of the early types of air compressors water was introduced through the 
inlet valves during the suction stroke; but this is an objectionable plan, because 
it has little effect on the heat produced until the discharge of the air, and fur- 
thermore, there is the danger of introducing too much water, and thus reducing 
the volume of air and endangering the cylinder heads. 

The presence of moisture in the air reduces the heat loss, hence, as shown 
by Table No. 4, less power is required to compress moist than dry air. It is not 
necessary to inject water during compression in order to gain this advantage, as 
the atmosphere is usually moist. The presence of moisture in the air has an im- 
portant bearing upon the compression, transmission and use of air. Be- 
fore compressed air became generally used, its value was thought to be prohib- 
itive, mainly because it was said that the air would freeze. This freezing was. 
of course, nothing more than the formation of ice due to the presence of moist- 
ure in the air, this moisture having been first deposited in the shape of water by 
expansion and cooling, and afterwards, the temperature going down below the 
freezing point, it l)ecanic ice. This has some time since ceased lo be a serious 
matter, and on the whole the presence of the moisture has been found to be more 
beneficial than otherwise, because by increasing the .specific heat of the body 
with which it is in contact, it reduces the temperature during compression and 
lends to increase it during expansion. In transmission it is simply necessarv 
to keep the temperature from falling below the dew point, or to put in suitable 



30 



PRODUCTION. 



receivers for draining the pipes. Where reheaters are used, the presence of 
moisture is decidedly advantageous. 

The amount of moisture in the atmosphere varies with the climate. Air 
is never perfectly dry; never, except in rare instances, does it contain less than 
25 per cent, of the moisture necessary to saturate it. It is not an uncommon thing 
to read in the meteorological reports in the newspapers during the summer that 
the moisture during an oppressively hot day reached 98 per cent., and even 99 
per cent. In winter it is usually 80 or 85 per cent. At 65 per cent, we consider 
it moderately dry; 50 per cent, being commonly called dry air. 

Otto Van Guericke invented the air-pump in 1650. In 1753 Holl used an 
air engine for raising water. At Ramsgate Harbor, Kent, in the year 1788, 
Smeaton invented a "pump" for use in a diving apparatus. In 185 1, William 
Cubitt, at Rochester Bridge, and a little later an engineer, Brunei, at Saltash, 



»tStl>VOllt 




Fig. 6. — Sommeiller Air Compressor used at the Mt. Cenis Tunnel. 



used compressed air for bridge work. In 1852, Colladon patented the application 
of compressed air for driving machine drills in tunnels. The first notable use of 
compressed air is due to Prof. Colladon, of Geneva, whose plans were adopted 
at the Mont Cenis tunnel. M. Sommeiller developed the Colladon idea and con- 
structed the compressed air plant illustrated in Fig. 6. 

The Sommeiller compressor was operated as a ram, utilizing a natural 
head of water to force air at 80 pounds pressure into a receiver. The column of 
water contained in the long pipe on the side of the hill was started and stopped 
automatically, by valves controlled by engines. The weight and momentum of 
the water forced a volume of air with such shock against a discharge valve that 
it was opened and the air was discharged into the tank; the valve was then 
closed, the water checked ; a portion of it was allowed to discharge and the space 
was filled with air, which was in turn forced into the tank. The efficiency of 
this compressor was about 50 per cent. 



PRODUCTION. 



31 



At the St. Gothard tunnel, begun in 1872, Prof. Colladon first introduced 
the injection of water in the form of spray into the compressor cylinder to ab- 
sorb the heat of compression. 

Fig. 7 illustrates the air cylinder of the Dubois-Francois type of compres- 
sor, which was the best in use about the year 1876. This compressor was exhib- 
ited at the Centennial Exposition and was adopted by Mr. Sutro in the construc- 
tion of the Sutro tunnel. A characteristic feature seems to be to get as much 
water into the cylinder as possible. The water which flooded the bottom of the 
cylinder arose from the voluminous injection; this water was pushed into the 




Fig. 7. — Dubois & Francois, 1876. 



end of the cylinder and some of it escaped with the air through the discharge 
valve. 

An improved pattern of this compressor is shown in Fig. 8. 

The first air compressor used on a large scale for practical work in Amer- 
ica is shown in Fig. 9. 

This machine was used at the Hoosac Tunnel, being built a little prior to 
1866. The design was made under the direction of the Massachusetts State Com- 
mission, of which Mr. John W. Brooks was chairman and Mr. Thomas Doane, 
chief engineer for tunnel construction. It is believed that Mr. Doane deserves 
the largest share of credit for the invention and development of this compressor, 
and it is to the credit of these early designers to note that after the completion 
of the Hoosac Tunnel the compressor was transferred to the Marble Quarries, at 
Sutherland Falls, Vt. (now called Proctor), and that it has been used continu- 
ously up to the present time, compressing air to about 40 pounds to the square 
inch. Rock drills and channeling machines of modern construction are now 
using this air for quarrying the beautiful marble of Vermont. 

The first channeling machine was tried in this quarry perhaps with com- 
pressed air furnished by the Hoosac Tunnel compressor. 

The compressor is so simple that it may be readily understood by looking 
1 the plan. It consists of 4 horizontal air cylinders, the pistons of which arc 



32 



PRODUCTION. 



propelled by a turbine wheel. The cylinders are single acting, the air being ad- 
mitted through poppet valves placed in the piston. Each cylinder is 13 in. in 
diameter by 20 in. in stroke. It was originally intended for a speed of 120 revolu- 
tions per minute, but it has been run over 70 revolutions. The cooling arrange- 
ment applied to this compressor was simply an injection of water through the 
inlet valves into the cylinders, though since its use at Hoosac Tunnel, injection 




Fig. 8.— Dubois & Francois, 1884. 



has been abandoned, and a simple stream of water from a jet is allowed to play 
upon the cylinders. 

These illustrations are interesting from an historical point of view, as indi- 
cating the line of thought which early designers of air compressing machinery 
followed. As the necessity for compressed air power grew, inventors turned 
tiieir attention to the construction of air-compressing engines that would t:ombine 
tmciency with light weight and economy of space and cost. The trade demanded 
compressors at inaccessible localities, and in many cases it was preferred to sac- 
rifice isothermal results to simplicity of construction and low cost. 

It IS evident that an air compressor which has the steam cylinder and the 
air cylinder on a single straight rod will apply the power in the most direct man- 
ner, and will involve the simplest mechanics in the construction of its parts. It 
IS evident, however, that this straight line, or direct construction, results in an 
engine which has the greatest power at a time when there is no work to perform. 
At the beginning of the stroke, steam at the boiler pressure is admitted behind 
the piston, and as the air piston at that time is also at the initial point in thv 



PRODUCTION. 



33 



roke, it has only free air against it. The two pistons move simultaneously as 
le resistance in the air cylinder rapidly increases as the air is compressed. To 
[■et economical results it is, of course, necessary to cut off in the steam cylinder 
so that at the end of the stroke, when the steam pressure is low, as indicated by 
the dotted line (Fig. lo), the air pressure is high, as similarly indicated in the 
other cylinder. The early direct-acting compressor used steam at full pressure 
throughout the stroke. The Westinghouse pump applied to locomotives, is built 
on this principle, and those who have observed it work have perhaps noticed that 
its speed of stroke is not uniform, but that it moves rapidly at the beginning. 




Fig. 9. 



gradually reducing its speed, and then seems to labor until the direction of stroke 
is reversed. This construction is admitted to be wasteful, but in some , cases, 
notably that of the Westinghouse pump, economy in steam consumption is sacri- 
ficed to lightness and economy of space. 

Many efforts were made to equalize the power and resistance by con- 
structing the air compressor on the crank shaft principle, putting the cranks at 
various angles, and by angular positions of steam and air cylinders. Several 
types are shown in Fig. 11. 

Angular positions of the cylinder involve expensive construction antl un- 
steadiness. Experience has proved that there is nothing in the apparent djffi- 



34 



PRODUCTION. 



ciilty in equalizing the strains in a direct-acting engine. It is simply necessary 
to add enough weight to the moving parts, that is, to the piston, piston rod, fly 
wheel, etc., to cut off early in the stroke and secure rotative speed with the most 
economical results and with the cheapest construction. It is obvious that the 



PrtO-CLpla o'r \>vTctt C o n\ i^f e-s-b vo' 




J\ vv 



inc.. TO. — DIRECT COMPRESSION ILLUSTR.\TED IN THE STRAIGHT LINE AIR COMPRESSOR, 
IN WHICH THE MOMENTUM OF THE FLY WHEEL EQUALIZES THE PRESSURE. 



\Yc\t\a\J 



^ eVcvv ^.Y^ne, 




C^^^'do' 



Fig. II. 



theoretically perfect air compressor is a direct-acting one with a conical air cylin- 
der, the base of the cone being nearest the steam cylinder. This, from a practical 
point of view, is impossible. Mr. E. Hill in referring to the fallacious tendencies 
of pticnmatic engineers to equalize power and resistance in air compressors, says: 



PRODUCTION. 



35 



"The ingenuity of mechanics has been taxed and a great variety of devices 
have been employed. It is usual to build on the pattern of presses which do their 
work in a few inches of the end of the stroke and employ heavy fly wheels, 
extra strong connections, and prodigious bed plates. Counterpoise weights are 
also attached to such machines; the steam is allowed to follow full stroke, steam 
cylinders are placed at awkward angles to the air-compressmg cylinders and the 
motion conveyed through yokes, toggles, levers; and many joints and other 
devices are used, many of which are entire failures, while some are used with 
questionable engineering skill and very poor results." 

Fig. 12 illustrates the theory of Duplex Air Compressors. The hydraulic 
piston or plunger compressor is largely used in Germany and elsewhere on the 
Continent of Europe, but the duplex may be said to be the standard type of 
European compressor at the present time. It is also largely used in America. 
Fig. 12 shows the four cylinders of a duplex compressor in two positions of the 
stroke. It will be observed that each steam cylinder has an air cylinder con- 
nected directly to the tail rod of its piston, so that it is a direct-acting machine, 



>\' .^ 






bTfAnx 


*-m 






1 --J 






1 










r=Pf^- '-^ 


y 


■-.-.] 




:■■ 




' 










Fig. 12. 



except in that the strains are transmitted through a single fly wheel, which is 
attached to a crank shaft connecting the engines. In other words, a duplex air 
compressor would be identical with a duplex steam engine, except in, that the 
air cylinders are connected to the steam piston rods. The result is, as shown in 
Fig. 12, that at that point of the stroke indicated in the top section, the uppei^ 
right hand steam cylinder, having steam at full pressure behind its piston, is 
doing work through the angle of the crank shaft upon the air in the lower 
left hand cylinder. At this point of the stroke the opposite steam cylinder 
has a reduced steam pressure and is doing little or no work, because the 
opposite air cylinder is beginning its stroke. Referring now to the lower 
section, it will be seen that the conditions are reversed. One crank has turned 
the center, and that piston which in the upper section was doing the greatest work 
is now doing little or nothing, while the labor of the engine has been transferred 
to those cylinders which a moment before had been doing no work. 

This is the theory of the Duplex Compressor, but it can hardly be said 
to l)c true when applied in practice, because of the heavy fly wheel which is placed 
"11 the main shaft. This wheel lakes up and equalizes the power imparted by the 



36 PRODUCTION. 

steam pistons, and in fact it is the fly wheel which really does the work of com- 
pression at or near the end of each stroke. Heavy fly wheels are therefore essen- 
tial in order to produce the best results with duplex compressors. 

In the duplex pattern, the crank shafts being set quartering, as is the usual 
construction, the engine may be run at low speed without getting on the center. 
Each half being complete in itself, it is possible to detach the one when only half 
the capacity is required. 

Commercially the Duplex Compressor appeals to the trade in that one side, 
or a half duplex, is furnished with a fly wheel and outboard bearings designed 
for a complete duplex machine, so that at first, at a little more than half the ex- 
pense, one side is erected and when more air is needed the capacity of the plant 
is doubled by adding the other half. Where large capacities are required, the 
duplex will admit of larger air production with economical engines, and at less 
expense when the cost of the plant is considered in proportion to the volume of 
air furnished. 

Mr. John Darlington, of England, gives the following particulars of a 
modern air compressor of European type: 

"Engine, two vertical cylinders, steam jacketed, with Myer's expansion 
gear. Cylinders, 16.9 inches diameter, stroke 39.4 inches; compressor, two 
cylinders, diameter of piston 23 o inches ; stroke 39 •4 inches ; revolutions per 
minute, 30 to 40; piston speed, 39 to 52 inches per second; capacity of cylinder 
per revolution, 20 cubic feet ; diameter of valves, viz., four inlet and four outlet, 
5>2 inches ; weight of each inlet valve, 8 lbs. ; outlet, 10 lbs. ; pressure of air, 4 to 
5 atmospheres. The diagrams taken of the engine and compressor show that 
the work expended in compressing one cubic meter of air to 4 -21 effective atmos- 
pheres was 38,128 lbs. According to Boyle and Mariotte's law it would be 37,534 
lbs., the difference being 594 lbs., or a loss of i '6 per cent. Or if compressed 
without abstraction of heat, the work expended would in that case have been 
48,158. The volume of air compressed per revolution was 0*5654 cubic meters. 
For obtaining this measure of compressed air, the work expended was 21,557 
pounds. 

"The work done in the steam cylinders, from indicator diagrams, is shown 
to have been 25,205 pounds, the useful effect being 85^ per cent, of the power 
expended. 1 he temperature of air on entering the cylinder was 50 deg. Fah. ; on 
leaving. 62 deg. Fah., or an increase of 12 deg. Fah. Without the water jacket 
and water injection for cooling the temperature it would have been 302 deg. Fah. 
The water injected into the cylinders per revolution was 0.81 gallons." 

We have in the foregoing a remarkable isothermal re§ult. The heat of 
compression is so thoroughly absorbed that the thermal loss is only i -6 per cent. ; 
but the loss by friction of the engine is 14-5 per cent., and the net economy of 
the whole system is no greater than that of the best American dry compressor, 
which loses about one-half the theoretical loss due to heat of compression, but 
which makes up the difference by a low friction loss. 

The wet compressor of the second class is the water piston compressor, 
Fig. 13- 

The illustration shows the general type of this compressor, though it has 
been subject to much modification in different places. In America a plunger is 



PRODUCTION. 



37 



used instead of a piston, and as it always moves in water, the result is more 
satisfactory. The piston, or plunger, moves horizontally in the lower part of a 
U-shaped cylinder. Water at all times surrounds the piston and fills alternately 
the upper chambers. The free air is admitted through a valve on the side of 
each column and is discharged through the top. The movement of the piston 
causes the water to rise on one side and fall on the other. As the water falls 
the space is occupied by free air, which is compressed when the motion of the 
piston is reversed, and the water column raised. The discharge valve is so pro- 
portioned that some of the water is carried out after the air has been discharged. 
Hence there are no clearance losses. 

The chief claim for this water piston compressor is that its piston is also 
its cooling device, and that the heat of compression is absorbed by the water. 




Fig. 13. — Hydraulic or Wet Air Compressor. 



So much confidence seems to be placed in the isothermal features of this ma- 
chine that usually no water jacket or spray pump is applied. Mr. Darlington, 
who is one of the stanch defenders of this class of compressors, has found it 
necessary to introduce "spray jets of water immediately under the outlet valves," 
the object of which is to absorb a larger amount of heat than would otherwise be 
effected by the simple contact of the air with the water-compressing column. 
Without such spray connections, it is safe to say that this compressor has 
scarcely any cooling advantages at all, so far as air cooling is concerned. Water 
is not a good conductor of heat. In this case only one side of a large body of 
air is exposed to a water surface, and as water is a bad conductor, the result is 
that a thin film of water gets hot in the early stage of the stroke, and little' or 
10 cooling takes place thereafter. The compressed air is doubtless cooled before 
it gets even as far as the receiver, because so much water is tumbled over into 
the pipes with it ; but to produce economical results, the cooling should take place 

tg compression. 



m 



38 PRODUCTION. 

Water and cast iron have about the same relative capacity for heat at equal 
volumes. In this water piston compressor v^^e have only one cooling surface, 
which soon gets hot, while with a dry compressor, with water jacketed cylinders 
and heads, there are several cold metallic surfaces exposed on one side to the 
heat of compression, and on the other to a moving body of cold water. 

But the water piston advocate brings forward the question of speed. It 
is said that, admitting that the cooling surfaces are equal, we have in one case 
more time to absorb the heat than in the other. This is true, and here we come 
to an important class division in air compressing machinery high speed and short 
stroke as against slotu speed and long stroke. Hydraulic piston compressors are 
subject to the laws that govern piston pumps, and are, therefore, limited to a 
piston speed of about lOO feet per minute. It is quite out of the question to run 
them at much higher speed than this without shock to the engine and fluctuations 
of air pressure due to agitation of the water piston. The quantity of heat pro- 
duced — that is, the degree of temperature reached — depends entirely upon the 
conditions in the air itself, as to density, temperature and moisture, and is en- 
tirely independent of speed. We have seen that it is possible to lose 21 -3 per 
cent, of work when compressing air to five atmospheres without any cooling ar- 
rangements. With the best compressors of the dry system one-half of this loss 
is saved by water jacket absorption, so that we are left with about 11 per cent., 
which the slow moving compressor seeks to erase. We are quite safe in saying 
that the element of time alone in the stroke of an air compressor could not pos- 
sibly effect a saving of more than half of this, or 5^ per cent. Now, in order to 
get this 5^ per cent, saving, we reduce the speed of an air-compressing engine 
from 350 feet per minute to 100 feet per minute. We must, therefore, in one case 
have a piston area three and one-half times that of the other in order to get the 
same capacity of air, and in doing this we build an engine of enormous propor- 
tions, with heavy moving parts. We load it down with a large mass of water, 
which it must move back and forth during its work, and thus we produce a per- 
centage of friction loss alone equal to twice or even three times the sH per cent, 
heat loss which is responsible for all this expense in first cost and in main- 
tenance, but which really is not saved, after all, unless water injection in the 
form of spray also forms a part of the system. 

It is obvious that cost of construction and maintenance have much to do 
with the commercial value of an air compressor. The hydraulic piston ma- 
chine not only costs a great deal more in proportion to the power it produces, but 
it costs more to maintain it, and it costs more to run it. It is not an uncommon 
thing to hear engineers speak of the hydraulic piston compressor as the "most 
economical" machine for the purpose, but that it is so "expensive" and takes up so 
much room, and requires such expensive foimdations that, unless persons are 
"willing to spend so much money," they had better take the next best thing, a high 
speed machine. 

The hydraulic piston compressor has one solitary advantage, and that is, 
it has no dead spaces. It was conceived at a time when dead spaces were very 
serious conditions. Valves and other mechanism connected with the cylinder 
of an air compressor were once of such crude construction that it was impossible 
to reduce the clearance spaces to a reasonable point, and furthermore, the valves 



PRODUCTION. 39 

'were heavy and so complicated that anything like a high speed would either break 
them or wear them out rapidly, or derange them so that leakages would occur. 
But we have now reduced inlet and discharge valves and all other moving parts 
connected with an air cylinder to a point of extreme simplicity. Clearance space 
is in some cases destroyed altogether by what is, as it were, an elastic air head 
which is brought into direct contact with the piston. All this reduces clearance 
to so small a point that it has no influence of any consequence. The moving 
parts are made extremely simple. 

Mr. Sturgeon, of England, has applied a most ingenious and successful 
inlet valve, which is opened and closed by the friction of the air piston rod 
through the gland. Mr. Sergeant in America has introduced the piston inlet 
valve, which is opened and closed by its own inertia. We have, therefore, 
reached a point at which high speed is made possible. 

In the single or straight line compressor it is difficult to equalize power 
and resistance with long strokes. The speed will be jerky, and when slow the 
fly wheel rather retards than assists in the work of compression. This action 
tends to derange the parts and makes large bearings a necessity. The piston in 
a long stroke compressor travels through considerable space before the pressure 
reaches a point where the discharge valve opens, and after reaching that point it 
has to go on still further against a prolonged uniform resistance. This makes 
rotative speed difficult in single direct acting machines. During the early part of 
the stroke, the energy of the steam piston must be stored up in the moving parts, 
to be given out when the steam pressure has been reduced through an early cut- 
off. With a short stroke and a large diameter of steam cylinder we are able to 
get steam economy or early cut-off and expansion without compounding. 

In compressors of the single or direct acting type with steam and air cyl- 
inders of equal diameter it is possible to obtain a pressure of air twice as great as 
the boiler pressure. This apparent enigma is made plain when it is understood 
that at the beginning of the stroke there is no resistance in the air cylinder. The 
steam end at this point has its greatest power, and the supply may be cut-off and 
the steam expanded in proportion to the pressure required in the air end, and 
the speed of the machine. The indicator card shows a large volume and low 
pressure in the steam end, and a smaller volume and higher pressure in the air 
end, so that what is made up in the air card by high pressure is represented in 
the steam card by greater volume, and the area of one is nearly equal to that of 
the other. This can be seen by referring to Fig. lo. 

If we omit the cut-off on the steam end the pressure, instead of following 
the dotted lines, will be maintained at its maximum throughout the stroke, while 
the air pressure, or resistance, does not reach the steam pressure until the piston 
has passed the center of the cylinder; hence if there is sufficient inertia in the 
moving parts, there will be no difficulty in getting an air pressure higher than 
that of the steam. 

CLEARANCE. 

tThe early designers of air compressors, as shown in the Dubois & Francois 
llustrations (Figs. 7 and 8), mention clearance loss in air compressors as a very 
erious matter. Even at the present time some air compressor manufacturers 
I 



40 PRODUCTION. 

admit water through the inlet valves into the air cylinder, not so much for the 
purpose of cooling as to fill up the clearance spaces. A long stroke involving 
expensive construction is sometimes justified by the claim that a saving is effected 
by reduced clearance losses. 

Clearance in a properly designed compressor is a loss of volume only, not a 
loss of power. Let us assume, for the sake of illustration, that we are com- 
pressing air with a machine which is provided with so efficient a cooling device 
that all of the heat of compression will be absorbed as soon as produced. In 
other words, that we can compress air isothermally. In such a machine as this 
there will be a slight loss of power due to clearance space, because we would 
have a certain volume of air in the cylinder at each stroke, and upon which work 
had been done and heat produced, that heat having been absorbed and the air 
being retained in the cylinder. In other words, we would have a production 
and abstraction of heat, which would represent power lost. Isothermal com- 
pression is practically impossible ; hence we do not abstract the heat from the 
compressed air in the clearance space, but a large portion of this heat remains, 
and<fects expansively upon the air, imparting its power to the piston at the mo- 
ment of reversal of stroke. A reasonable clearance space behind the air piston 
serves a useful purpose in overcoming the inertia of the piston and moving parts 
acting like a spring at the end of each stroke. 

The clearance space in modern air compressors of the best design (includ- 
ing the counter-bore and discharge valve clearance) varies from .002 to .0094 of 
the volume of free air furnished by the cylinder. The variation is somewhat 
dependent upon the length of stroke of the machine. At 75 lbs. pressure, and 
making due allowance for increased volume of air due to heat, the clearance loss 
of volume varies from .01 to .047, or from one to five per cent, of the air when 
compressed. The actual space between the piston and the head at the end of the 
stroke being 1-16". 

It must not be inferred that the designers of an air compressor may 
neglect the question of clearance ; on the contrary, it is a very important con- 
sideration. If we have a large clearance space in the end of an air compressor 
which is used to compress air to high pressures, we may readily understand a 
condition of things that would result in no discharge of compressed air at all, 
because of too large a clearance space. The entire volume of the cylinder might 
be compressed and retained in the clearance space, and the compressor will take 
in no free air on the return stroke, because the clearance space air when expanded 
is sufficient to fill the cylinder at normal or atmospheric pressure. 

Loss in capacity of air compressors by clearance is in direct proportion to 
the pressure. 

Owing to the loss of capacity by clearance in high pressure compressors, it 
is important that the cylinders be compounded. By compounding the air in the 
cylinders the clearance loss is reduced because of the reduced density in the air 
in the clearance space. 

Builders of air compressors employ three methods to reduce the clearance 
loss: (t). By long strokes of piston, so that the percentage of cylinder volume to 
that of clearance space is reduced to a minimum. (2), By filling the space with 



PRODUCTION. 41 

water. (3), By not allowing the full reservoir pressure to accumulate in the 
clearance space above the inlet valve. 

The long stroke plan is the best for reducing clearance, except in machines 
of the single type, where economical compression and rotative speed cannot be 
accomplished with a long stroke. The use of water to fill clearance spaces has 
been referred to previously when treating of water injection. 

The clearance in the initial cylinder is filled with air at a pressure less than 
the receiver pressure; and as the diameter of the high pressure cylinder is small, 
the loss in capacity by clearance is reduced. Mr. E. Hill states that a single type 
of compressor should have a stroke of 68 in., in order that its clearance loss shall 
not exceed that of a compound compressor of 24 in. stroke when both compressors 
are forcing air against 60 pounds pressure. 

Fig. 14 illustrates the effect of clearance in loss of volume in an air com- 
pressor. The diagram illustrates a typical case in compressors of cheap design 
and manufacture, the loss in volume amounting to about 20 per cent. 

Unnecessary complications have been applied to air compressors to over- 
come clearance loss. Mr. Sturgeon has designed an air cylinder with lifting 




Fig. 14. — Showing Effect of Clearance. 

heads, so that the piston slightly raised the head at each stroke, thus reducing 
clearance to an exceedingly small figure. 

A simple method of reducing the clearance loss is by a passage or by- 
pass grooves in the end of the cylinder arranged in such a way that when the 
piston reaches the end of the stroke it passes over the grooves and thus allows 
the high pressure air, which is confined in the clearance space, to pass to the 
other side of the piston. The air in such cases is usually allowed to pass through 
the grooves at a velocity not exceeding 100 ft. per second. This plan is, how- 
ever, subject to objections, and it is doubtful that there is anything gained by 
it. The load on the air piston is suddenly removed when the grooves are un- 
covered, and thus the cushion behind the piston is destroyed, and unless the 
cushion in the steam end is effective the compressor will pound badly at the end 
of each stroke. 

The commonest form of inlet valve applied to air compressors is the pop- 
pet. It is plain that as soon as the piston starts from the extreme point of stroke 
nearest the cylinder head, it is followed by the air confined in the clearance space 
until that point is reached when the pressure in the cylinder is equal to the pres- 
sure outside. From this point the action of the piston is now to produce a par- 
tial vacuum within the cylinder, resulting in opening the poppet inlet valves 



42 PRODUCTION. 

against the tension of the spring which holds them to their seats. The result of 
all this is that the poppet valve construction does not admit of a full air cylinder, 
as no air from the outside is admitted during a portion of the stroke. Even after 
the inlet valves are opened there is more or less friction through the passages 
which reduces the atmospheric pressure. There is seldom less than one pound 
per square inch difference in pressure between the air within and without the 
cylinder. This, though apparently small, results in a very serious reduction of 
efficiency. 

A common defect in air compressor construction is insufficient space for 
proper delivery after compression. The discharge valves and discharge pas- 
sages are so contracted as to offer considerable resistance to the passage of the 
air which should be discharged at the same velocity as that at which the piston 
moves. As the area in the cylinder head is usually small, the volume of valve 
area is restricted to the minimum. Heavy springs are used in order to prevent 
the valves from hammering, and the result of this is a loss of power. It is not 
a difficult matter to admit the air through a valve which is moved by direct me- 
chanical connection, and without springs, but many difficulties are in the way 
of positive movement in discharge valves. The exact point when it is desired to 
admit the air is fixed for all pressures and temperatures, but not so with the 
point of discharge. This varies in proportion to the pressure, and this is effected 
more or less by the conditions of temperature, dryness and density of inlet air, 
and the cooling effect during compression. It would not do to hold the discharge 
valves closed after the pressure in the cylinder has reached the point of pressure 
in the receiver. Equally serious in loss of efficiency would it be to open a dis- 
charge valve before the air in the cylinder has reached the receiver pressure; 
hence the poppet form of discharge valve is generally used. 

Designers of air compressors seldom consider the velocity at which the 
compressed air is discharged from the cylinder. When the discharge valves are 
first opened the piston is moving with considerable velocity, which discharges the 
air in some cases at a velocity of 200 ft. per second. This is, of course, gradually 
reduced as the piston nears the end of the stroke. 

Poppet-valves when used either for inlet or discharge should be small 
in diameter and light in weight. Various designs involving poppet valves of 
large diameter have been applied to compressors, but they have invariably failed 
because the increased inertia of a large valve will pound the seats and break the 
springs. Where poppet valves are used, a large number of small, light valves is 
the best construction. The movement of a poppet valve should be as short as 
possible, in order to minimize the wear which results from constantly striking the 
seat. 

It is important in designing an air compressor to provide ample inlet space, 
so that the cylinder will be filled with air and thus maintain the full volumetric 
capacity of the machine. The usual area of inlet is i-io, the area of the piston, 
though in slow speed compressors this might be reduced considerably. Com- 
pressors provided with a concentrated inlet through which the air is drawn alter- 
nately at one end and the other of the piston, do not require as large an area of 
inlet as the intermittent type, because the air when once started through the inlet 
is maintained constantly moving in one direction and toward the cylinder; thus 



PRODUCTION. 



43 



draft of air is produced which materially aids in piling up the pressure at the 
>int of reversal of stroke. It must be borne in mind that while the piston is 
Irawing the air into the cylinder its speed is variable. At the beginning, when 
irning the centre it is slow, increasing rapidly until it reaches its maximum 
)eed at the centre of the stroke and then decreasing until it reaches the point 
rhen the inlet valve closes. At that point the piston is at a standstill, and inas- 
luch as its speed has been gradually reduced, it is natural to expect that the 
;locity of the air when started at a high rate is to a certain degree maintained, 
isulting in a completely filled air cylinder. 

Table No. 5 gives the proportions of air cylinders, valves and clearance 
)aces in air compressors of the best modern design. In this case the inlet is 
mcentrated; that is, the air is drawn into the cylinder through a piston inlet 

Table No. ;. — Proportions of Air Cylinders. 





Per Ct. 

of 
Clear- 
ance. 


PerCt.of 




Air Inlet. 




Air Discharge 


sizes of Air 


Clearance 
Air Com- 
pressed 
to 76 lbs. 


Cylin- 
der. 












Cylinders. 
















Free 


Sq. in. 


Size Of 


Area of 


Per Ct. 


No of 


Area of 


PerCt. 




Air. 




Pipe. 


Pipe. 


of Area. 


Valves 


Valves. 


of Area. 


10^ in. X 12 in. 


.0094 


.047 


78 


2 in. 


3.14 


.04 


2 


5.4 sq. in. 


.07 


12^ in. X 14 in. 


.0086 


.043 


113 


21^ in. 


4.9 


.043 


2 


88 


.078 


14>4 in. X IS in. 
16H in. X 18 in. 


.0066 


.033 


154 


3 in. 


7. 


.045 


3 


13 2 


.085 


.0066 


.0330 


201 


3>^in. 


9.6 


.047 


3 


13 2 


.065 


1H>4 in. x24in. 


.0<>49 


.0225 


255 


4 in. 


13. 


.0.51 


8 


35.2 sq. in. 


.14 


20>4 in. x24in. 


.0f)49 


.0225 


314 


4^ in. 


16. 


.0.^1 


8 


35.3 


.11 


2214 in. X 24 in. 
30K in. X GO in. 


.0049 


.0225 


380 


5 in. 


20. 


.053 


10 


44. 


.116 


.002 


.01 


707 


6 in. 


28. 


.04 


18 


79.2 


.112 


36>4 in. X 4S in. 


.002 


.01 


IO18 


7 in. 


38.5 


.038 


20 


88. 


.086 



The clearance on the ends of cylinders is 1-16 inch on each end, and is the same on all 
cylinders, for pressure up to 100 Ib.s. On high pressure cylinders the end clearance is reduced 
to o. The percentage of clearance at 75 lbs. is taken as 5 times free air. thus allowing heating. 



tube, hence five per cent, of the area of the cylinder is sufficient for the inlet. 
These dimensions have been practically tested, and in no case, even at the maxi- 
mum speed of the machine, has there been any evidence of contraction. 

The discharge valve area depends upon the speed of the compressor, and 
for the best results should be about ten per cent, of the cylinder area for a piston 
speed of 300 feet per minute, or fifteen per cent, for a speed of 450 or 500 feet. 

In the usual air-compressor plant the free air is taken in from the engine- 
room. This is a mistake which is so apparent that it is difficult to account for 
its existence. It is not only desirable to compress clean, dry air (which is not 
usually found in the engine-room), but the economy and capacity of an air-com- 
pressing plant are largely dependent upon the temperature of the intake air. 
A low temperature increases the capacity, and adds to the efficiency of the 
machine. 

A concentrated inlet connecting the valves with a point outside the engine- 
room is the best construction. A chimney made of wood will serve the purpose 
very well, though cooler air can be obtained by drawing it from a well. The 



44 



PRODUCTION. 



presence of water in the well is no disadvantage, provided the water is cold. The 
intake air might advantageously be passed through cold water, or subjected to a 
spray of water for the purpose of reducing its temperature and destroying the 
impurities. 

For every five degrees that the temperature of the intake air is lowered 
below that of the engine-room, there is a gain of one per cent, in volume. In 
summer only a few degrees difference can be obtained, but in winter the differ- 
ence between the air inside and outside is often fifty degrees. 

Mr. E. Hill has compiled the following table, showing the discharge of a 
compressor having an intake capacity of i,ooo cubic feet of free air per minute; 
the temperature of the intake air varying from zero to iio°, and in each case 
being discharged at a uniform temperature of 62° F., and at atmospheric pres- 
sure : 



Temperature 

of 
Intake Air. 


Volume taken 

into 

Compressor. 


Volume discharged, if 

measured at 62 degrees 

and atmospheric 

pressure. 





1,000 cubic ft. 


1,135 


cubic ft. 


32 


1,000 " 


1,060 




62 


1,000 " 


1,000 




75 


1,000 " 


975 


" 


80 


1,000 " 


966 




90 


1,000 " 


949 


« 


100 


1,000 " 


932 


(( 


no 


1,000 *• 


916 


" 



Mr. R. A. Parke, in a paper read before the New York Railroad Club, 
illustrated the great importance of supplying the compressor with cold air, as 
follows : 

"With an ordinary single-stage compressor, furnished with no cooling 
appliance, the delivery temperature of the air at the compressor is about 437 de- 
grees. It may be assumed that, in every ordinary case of transmission, the tem- 
perature of the air falls to that of the locality where it is used, with an accom- 
panying shrinkage of volume, so that, in the present example, the temperature 
of the air used would be 60 deg., and each cubic foot of air delivered at the com- 
pressor shrinks to .58 cubic feet before being used. If the temperature of the 
atmospheric air received in the compressor were 40 deg. instead of 80 deg., the 
delivery temperature would be but 371 deg., and, when cooled to 60 deg., the 
shrinkage of each cubic foot delivered would be only to .626 cubic feet. Thus 
eight per cent, greater volume of atmospheric air, at a temperature of 80 deg., 
must be compressed than would be necessary if the temperature of the air were 
40 deg." 

Low temperature of intake air is so important that the plants established 
for the purpose of compressing air for power distribution should be located with 
this question prominently in mind. An ice-making plant, or a cold-storage room, 
is the best place for an air-compressor. In such a place as this, with the tem- 
perature of the intake air at or near zero, the compressor, provided with com- 
pound cylinders jacketed by a circulation of cold brine, and thoroughly cooled 



PRODUCTION. 45 

between the stages, we might produce compressed air at a low temperature and a 
high efficiency. This cold, dry air, distributed over or under ground (thus in- 
creasing its temperature in transit), and heated before use, might develop an 
efficiency beyond that which is possible in the use of electricity, hydraulics, or 
any other form of secondary power. 

AIR COMPRESSING MACHINES. 

In describing air pumps or compressors we will endeavor to confine our- 
selves strictly to such machines as are at the present time in practical operation. 
The large field of patented designs, antiquated types and such like, will be 
omitted. 

The simplest form of air pump is the little apparatus with which every one 
is familiar, namely, the pump for inflating the bicycle tire. Fig. 15. 



5««i«iiiPii|iiip^iia »^ "3="^^^ ■ ■- - ^^-:— ::-:' '"^.. 



Fig. 15. — A Bicycle Air Pump. 

This little pump is made both single and double acting, the single acting 
device being the simplest form of air compressor. The piston rod is the dis- 
charge passage, the piston packing being a simple leather washer which is aided 
by the air pressure in forming a perfectly tight joint, the piston is fixed, the 
cylinder being grasped in the hand and forced forward. This little device is 
interesting in that its use reminds us of an important fact in air compressing — 
the development of heat. After a few strokes the heat produced is quite per- 
ceptible. This heat is not due to friction, but it represents the conversion of the 
work done by the hand into heat. When there is little resistance or little air in 
the tire the heating is not noticed because but little work is done. As soon, how- 
ever, as the tire becomes inflated the action of the pump is more difficult to per- 
form and the heat increases. It is not an uncommon experience for this pump 
to fail to act, due to the sticking of the little check valve which connects the 
cylinder through the piston rod with the interior of the tire. When this valve is 
stuck it will be noticed that on pressing the pump cylinder forward and letting it 
go, it is quickly pushed back to its original position, heat has been produced and 
there is evidently a pressure within the cylinder tending to hold its front end 
firmly against the piston. Where does this pressure come from? We had only 
free air and no pressure before giving the stroke to the cylinder, and now it has 
returned to its original position and tends to go further. There has been no 
leakage from the tire because the check valve is tight and immovable. We have 
simply compressed a volume of confined air as we would compress a spring, yet 
unlike a spring it apparently has power to go further than its original position. 
This is because we have done work upon the air, it has failed to get away, heat 
has been produced because the air has done no work in return. This heat ex- 
pands the air, thus giving it additional power to recover, and as the cylinder is 
a light thing it is pushed back to its original position with but little expenditure 
"f energy. If the pump and its confined air are now allowed to cool down to the 



46 



PRODUCTION. 



temperature of the surrounding atmosphere the tension in the cylinder will be 
relieved and the original conditions will be recovered. Even a bicycle pump may 
teach us important lessons in thermodynamics. 

Hand pumps of larger sizes are made for medical service and other uses, 
the principle being simply that of a piston forced backward and forward in a 
cylinder. Where larger volumes of air are required hand pumps provided with 




Fig. i6. 



fly-wheels and operated by one or more men have been introduced and are largely 
used. The commonest pattern is the Vertical Belt or Hand Air Pump (Fig. i6), 
which may be run by hand or by power as desired. 

The High-Pressure, Vertical, Belt Air Pumps are built in response to 
many applications for a reliable and small belt or hand power air pump to com- 
press air to 300 pounds pressure. There have been several more or less impor- 
tant improvements made on the original design, and on the larger sizes the suc- 
tion and discharge pipes are cast solid to the cylinder. 



PRODUCTION. 



47 



They can be bolted against any pillar, wall or strong board, and driven by 
a heavy pulley wheel of such diameter and width of face as required to attain the 
pressure wanted; when required to be worked by hand power they are provided 
with a handle in fly-wheel, which can be run by one or two men to a proportionate 
pressure. 

The air brake pump is the simplest form of power air compressor with 
which we are familiar. Furthermore it is a machine so largely used that it de- 

TaBLE 6. — ^VERTICAL, BELT OR HAND AIR PUMPS. PRICE LIST. 



Number. 


Diameter 

of Air 
Cylinder 
in inches. 


Length of 

Stroke in 

inches. 

6 
6 
6 
6 
6 
6 
6 
6 


Number of 
Revolutions 
per minute. 


Cu. Ft. Meas- 
urement of 

Free Air Com- 
pressed per 
minute. 


Attainable Air i 

Pressure in t,,;„^ 
lbs. per square : ^'^'^^• 
inch. 1 


1 
2 
3 
4 
5 
6 
7 
8 


2 
|M 

4 
5 

8 

8 


150 
150 
150 
140 
140 
130 
130 
120 


2 
3 

,§ 

20 


300 1 $50 
SCO ' 50 
250 60 
200 70 
150 80 
100 90 
50 110 
30 130 



serves more than a passing notice. There are more air compressors used for the 
purpose of operating brakes than for all other purposes combined. It has been 
estimated that 30,000 of these pumps are in service. Fig. 17 illustrates the im- 
proved 9j^-inch Westinghouse pump. 



THE NINE AND ONE-HALF INCH IMPROVED AIR PUMP. 
DESCRIPTION OF THE AIR BRAKE PUMP. 

60. Top Head, complete (Includes parts Nos. 72, "jz^ 74, 75, ^d, 83, 84, 85, 
108, 109 and 8 of no.) 

61. Steam-cylinder, complete. (Includes parts Nos. 90, 91, 92, 93 and 94.) 

62. Center Piece, complete. (Includes parts Nos. 2 each of 95, 96 and 

97.) 

63. Air-cylinder, complete. (Includes parts Nos. 4 of 86, 2 each of 87, 

88 and 89, and i each of 90, 91, 92 and 106.) 
Lower Head. 

Steam Piston and Rod. (Includes 2 each of 67 and 68, 69 and 2 of 70.) 
(Includes 2 of 67.) 



64. 
65. 
66. 

67. 
68. 

69. 
70. 

71. 
72. 

1Z- 



Air Piston, Complete. 
Piston Packing Ring. 
Piston Rod Nut, 
Reversing- Valve Plate. 
Reversing- Valve Plate Bolt. 
Reversing- Valve Rod. 
Reversing- Valve. 
Reversing- Valve Chamber Bush. 



48 



PRODUCTION. 




Fig. 1/ — THE NINE AND ONE-HALF INCH IM.PROVED AIR PUMP. 



74. Reversing- Valve Chamber Cap. 

75. Main Valve Bush. 

76. Main Piston Valve, complete. (Includes Nos. -/-j, 2 of 78, 79, 2 of 80, ' 

81 and 4 of 82.) 

']']. Large Main Valve Piston Head. (Includes 2 of No. 78.) 

78. Large Main Valve Piston Packing Ring. 

79. Small Main Valve Piston Head. (Includes 2 of No. 80.) 
8q. Small Main Valve Piston Packing Rin§. 



PRODUCTION. 



49 



_.^ ^IU.►.V»U^/C Ou.-.~<» 




Fig. 17 — THE NINE AND ONE-HALF INCH IMl'KOVED AlU I'lMI' 



81. Main Valve Stem. 

82. Main Valve Stem Nut. 

83. Main Slide Valve. 

84. Right Main Valve Cylinder Head. 

85. Left Main Valve Cylinder Head. 

86. Air Valve. 

87. Air Valve Scat. 

88. Air Valve Cage, 



50 PRODUCTION. 

89. Valve Chamber Cap. 

go. One and One-fourth Inch Union Stud. 

91. One and One-fourth Inch Union Nut. 

92. One and One-fourth Inch Union Swivel. 

93. One Inch Steam Pipe Stud. 

94. Governor Union Nut. 

95. Stuffing Box. 

96. Stuffing Box Nut. 

97. Stuffing Box Gland. 

98. Air-cylinder Oil Cup. 

99. Short Cap Screw. 
100. Long Cap Screw. 

loi. Upper Steam Cylinder Gasket. 

102. Lower Steam Cylinder Gasket. 

103. Upper Air-cylinder Gasket. 

104. Lower Air-cylinder Gasket. 

105. Drain Cock. 

106. Air Strainer. 

107. One Inch Steam Pipe Sleeve. 

108. Left Main Valve Head Gasket. 

109. Right Main Valve Head Gasket, 
no. Main Valve Head Bolt. 

The air pump was designed without any thought of economy in the use 
of steam, the main consideration being economy of space, light weight and abso- 
lute reliability of action. Economy in the use of steam to compress the air is 
quite secondary to other and more important considerations. The use of a 
crank and fly-wheel is incompatible with economy of space, and a compressor 
with directly operated steam valves is a necessity. Because of this, the clearance 
space in the air cylinder must be about double that required in a fly-wheel ma- 
chine in order to avoid pounding. The steam ports, and especially the exhaust 
ports, must be contracted to prevent too high piston speed and consequent pound- 
ing when the pump is working against low air pressures. For the same reason 
the air discharge valves must also be small. The steam must be used non-ex- 
pansively as the resistance of the air pressure is greatest toward the end of the 
stroke, requiring the highest steam pressure at that time, and having no inertia 
of moving parts to help it around the center. 

Several years ago experiments were made by the Westinghouse Company 
extending over a period of two years, the purpose being to determine the ques- 
tion of steam economy. The eight-inch pump had been designed at a time when 
the average locomotive boiler pressure was about 120 lbs., and in order to 
secure an abundant supply of air the area of the steam piston Avas made about 
15 per cent, greater than that of the air piston. Between that time and the time 
when the tests were begun, the steam pressure of locomotive boilers liad become 
considerably increased, so that the greater area of the steam piston of the air- 
pump was no longer necessary. Experiments were conducted both with a sim- 
ple pump of suitable proportions to meet the changed conditions of service, and 



PRODUCTION. 



51 



with a compound pump, designed to attain the highest steam economy subject 
to the peculiar limitations of the service. 

The following descriptions of these tests are given by Mr. Parke in his 
paper before the New York Railroad Club. 

"The design of compound pump which seemed to best meet the require- 
ments has two steam cylinders, respectively 6 inches and lo inches in diameter, 
and each of lo inches stroke. Live steam is admitted to the smaller or high- 
pressure steam cylinder throughout the entire stroke, and, upon the return 
stroke, it expands into the larger or low-pressure steam cylinder, no live steam 
being admitted to the latter. All the ports of both steam cylinders are con- 
trolled by a single steam valve. There are two air cylinders, the diameters of 
which are respectively 6% inches and 9^ inches, and the stroke of each is lo 
inches. Atmospheric air is drawn into the larger or low-pressure air cylinder, 
and compressed therefrom into the smaller or high-pressure air cylinder. In the 
latter, the air is further compressed and delivered thence to the main reservoir. 
The piston of the high-pressure steam cylinder operates that of the low-pressure 
air cylinder, and the piston of the low-pressure steam cylinder operates that of 
the high-pressure air cylinder. The reversing valve is actuated by the high-pres- 

Table 7 — Steam Consumption. Different Types of Compressors. 



PUXP. 



H inch 

9V6 inch 

Compound 

B-inch Duplex. 



Simple compropsor, operated by simple engine 

Two-stage compressor, operated Dy compound, non-condensing engine. 



Volume of Free Air 

Compressed to 90 lbs. 

and Discharged. 



Per Min. 



26.3 cu. ft. 
44.9 " 



43.3 
29 4 

38.7 



Per Pound 
of Steam 

at 110 lbs. 
Pressure. 



1.85 cu. ft. 
2.49 



4.89 
2.06 



I 13.70 



sure steam piston. By this arrangement, the complete stroke of both the high- 
pressure steam piston and the low-pressure air piston is always assured, so that 
the pump cannot become dead, and a cylinder full of free air is always secured. 
The pump is operative at any steam pressure, the pressure at which the air can 
be delivered, depending, of course, upon the available steam pressure. 

"The design of simple pump resulting from these experiments was what 
is now known as the 9j4-incli pump, which has one steam and one air cylinder, 
v-ach gVj inches in diameter, with a lo-inch stroke. 

"In the tests of the various pumps, as to efficiency and capacity, the slcatn 
was condensed in a surface condenser, at atmospheric pressure and weighed, and 
the volume of air actually delivered was carefully measured. The conditions 
under which the tests were made were those of about the average service to be 
expected on the road; that is, the steam pressure used was 140 pounds and the 
pumps were required to deliver against an ajr pressure of 90 pounds. 



I 



52 ^ PRODUCTION. 

"Table 7 indicates the capacities and efficiencies of the various types of 
air-brake pumps under these conditions. For comparison, this table also indi- 
cates the volume of free air compressed to 90 pounds and delivered per pound 
of steam by a single-stage commercial-compressor, operated by an efficient sim- 
ple engine, and by a two-stage compressor, with intercooler, operated by a com- 
pound non-condensing engine. 

"The most striking feature of this table is the low efficiency of an air- 
brake pump, in comparison with a suitable compressor for a commercial supply 
of compressed air. Steam generation in stationery boilers for ordinary power 
purposes, is comparatively uniform, and the amount of fuel burned is practically 
proportional to the quantity of steam used. Under such conditions, unless the 
volume of compressed air required is very small or is required at irregular in- 
tervals and in imcertain quantities, it is not economy to use an air-brake pump 
in the place of a suitable compressor. 

"At the conclusion of these pump tests, it was decided to place the 9% 
inch pump upon the market, and, although the design of compound pump selected 
proves entirely satisfactory as to capacity, and requires only one-half the steam 
used by any air-brake pump in the market, it was decided to abandon any thought 
of offering it for sale. The reasons for the latter decision were chiefly the fol- 
lowing : 

"While the only working parts added to those of the simple pump are the 
additional pair of pistons and two additional air valves, a long experience has led 
to the conviction that simplification and not complication of air pump construction 
is what the best interests of the railroads require. The increased number of 
parts necessarily implies greater cost of maintenance and renewals, additional 
glands to be kept packed, a considerably increased number of sources of leakage, 
and the additional pair of cylinders materially increases the bulk and the weight of 
the pump. Ihis was regarded as the most serious objection to the introduction 
of a double pump. 

"Another serious objection is heating of the air end of the pump. It has 
been fully explained that compounding, or compressing in stages, is the method 
most to be preferred, when the air is cooled between the stages. It might also 
have been stated that for practical reasons, compounding the air, without cooling 
between the stages, is the worst method. By this method the air is theoretically 
delivered by the high-pressure air-cylinder at about the same temperature as it is 
from the air cylinder of a simple compressor; but the temperature of the air 
taken into the cylinder of a simple compressor is that of the atmosphere, while that 
of the air taken into the high-pressure air cylinder of the compound method (with- 
out cooling), is from 200 to 300 degrees above that of the atmosphere. It is evident, 
therefore, that the mean temperature of the air in the high-pressure air cylinder 
of the compound method, is very much higher than that of the air in a simple 
compressor. Indeed, it several times occurred, during the experiments referred 
to, that when a pump of the two air-cylinder type was allowed to run freely for 
twenty-five or thirty minutes, under the conditions stated, the maple plank upon 
the brick wall of the testing room to which the air cylinders were bolted, took 
fire. Such high temperatures of the high-pressure air cylinder are productive 
of serious evils. The two air cylinders are necessarily cast in one piece, of an 



PRODUCTION. 



53 



^irregular shape, and expansion by heat is inevitably accompanied by distortion. 

^This distortion at the air cylinders is aggravated by the still further increased 

temperature resulting from binding of the pistons. Unless the air pistons are 

)riginally fitted so loosely as to permit them to leak badly, they bind and cut, 

Fcausing great wear *and materially increasing the cost of maintenance. The dis- 

[tortion of the air cylinders always causes a large amount of leakage past the 

)istons, and the actual efficiency of such pumps is far below that calculated for 

lem. As it is wholly impracticable to introduce a cooling chamber upon a loco- 

lotive, in connection with the compound air cylinders, this type of pump seems 

be very imdesirable. 

"The one other important reason for abandoning the compound pump is 
lat steam economy in an air-brake pump is not of importance or value. Such a 



Fig. i8 — Direct-acting Steam Air Compressor. 



[conclusion may at first cause some surprise, but a little study of the conditions 
^ill fully support it. The steam requirements of a locomotive are very difficult 
les to meet, as the demand for steam to operate the engine fluctuates very 
reatly. The steam required by an air-break pump is not only an exceedingly 
mail proportion of the quantity generated, but it also fluctuates between limits 
widely apart. The air-brake pump does its heaviest duty while standing at sta- 
ions and in descending grades. 

"At such times the engines of the l9comotive use no steam, and such 

rteam as is then used by the air-brake pump would otherwise probably escape 

[through the pop valve. It is well known that, with the most careful firing, it is 

jractically impossible to prevent a waste of steam through the safety valve at 

times." 



54 PRODUCTION. 

In connection with a series of tests of a Baldwin compound locomotive 
upon the Baltimore & Ohio R. R., in 1890, the consumption of steam in various 
incidental ways was ascertained. The weights of steam which passed through 
the whistle, the blower and the pop valve, were computed. Instead of allowing 
the pop valve to blow off, a vent pipe from the steam dome was carried into the 
tender, and the weight of steam which would pass through it per second, when 
a valve in the pipe was opened, was ascertained. During the runs, when the 
steam reached such a pressure that the pop valve was on the point of blowing 
off, the valve in the vent pipe was opened, and, by noting the length .of time that 
it remained open, the quantity of steam which so escaped was easily computed. 
The number and lengths of blasts of the whistle were also noted, together with 
the time that the blower was used. The amount of steam used by the 8-inch air- 
brake pump was also computed. It was found that, after the train brake appa- 
ratus had become fully charged, the pump continued to run with an average 
speed of about 62 strokes per minute. This would«seem to indicate a considerable 
amount of leakage in the train pipe and connections. The writer has observed 
the operation of the 8-inch pump upon a considerable number of different trains, 
the air-brake apparatus of which was in such condition as he happened to find it. 
It was found that, after the brakes had been charged throughout the train, the 
number of strokes per minute made by the pump were from 24, for a four-car 
train, to 47 for a seven-car train, the average of all the cases observed being s^. 

During the trials of the Baldwin compound, three separate runs were 
made from Baltimore to Philadelphia, with the same train, making the same 
time, and with the same number of scheduled stops. In the report of Mr. George 
H. Barrus, the steam used in different ways during these runs was computed as 
follows : 

Whistle. Blower. Safety Valve. 

415 lbs 153 lbs 220 lbs. 

503 lbs 198 lbs 99 lbs. 

425 lbs 72 lbs 302 lbs. 

Average, 448 lbs 141 lbs 207 lbs. 

The average computed steam consumption of the air pump, under the con- 
ditions of its actual operation, was 690 lbs. Under the ordinary conditions of 
the brake apparatus in service, with the air pump making about 36 strokes per 
minute to keep up the pressure after the apparatus is once charged, the steam 
consumption, computed upon the same basis as that used in the report of these 
locomotive trials, would have been 400 lbs. It will be seen from these figures, 
therefore, that about the same quantity of steam was used by the whistle as is 
used by the air pump, and that, even in these locomotive trials, where unusual 
care was undoubtedly exercised in firing, the loss of steam by the safety valve 
was about half that w,hich should be used by the air pump. 

Under the ordinary conditions of service, although the steam used by the 
air pump is largely that which would otherwise be lost at the safety valve, it is 
most probable that the amount of steam lost at the safety valve is greater than 
that used by the air pump. 



r 



PRODUCTION. 



55 



It will thus be understood that, with the fluctuating conditions of loco- 
motive service, the steam consumption of the air-brake pump is an insignificant 
factor in the economy of steam production. It has never been demonstrated, so 
far as the writer is aware, that a locomotive hauling an air-braked train, with 
tlio brake apparatus in ordinarily good condition, consumes, in the long run. a 




Fig. 19. 




"■i'vm^w^jm^'r^ 



Fig. 20. 



pound more coal than the same locomotive, without an air pump, would use in 
hauling the same train when braked by hand, and there is no good reason to be- 
lieve that it would. 

Fig. 18 illustrates the simplest type of small air compressor built on the 
Straight Line or Direct Acting plan. The machine is designed for light trans- 
portation and for use in places where a compact, self-contained and very simple 




56 



PRODUCTION. 



compressor is wanted. The steam and air cylinders are connected to a cross- 
head which moves in guides arranged between the cylinders. The fly wheels, 
which are joined by connecting rods to this crosshead, are mounted in bearings 
close to the steam cylinder. Slide valves arc used operated by eccentrics, though 
in some of the larger sizes the adjustable cut-off serves to aid this type of ma- 
chine in fuel economy. The air cylinder is provided with poppet inlet and dis- 
charge valves, and is water jacketed. Simplicity of design is followed in ma- 
chines of this type, no claims being made to high fuel economy. 

Fig. 19 shows another type of simple, low cost, single or direct acting 
compressor. No crosshead is used. A single fly wheel with crank, shaft and 
connecting rod are placed between the cylinders. 

Fig. 20 is shown for the purpose of illustrating the English type of single 
or straight line compressor. The machine shown is known as "Schram's patent." 




A single cast iron bed plate is used, thus making the machine self-contained, and 
the fly wheel's crosshead and connecting rod are placed on the bed, the steam 
cylinder being located between these parts and the air cylinder. This construction 
brings the steam and air cylinders close together, but the machine is not as com- 
pact or as simple as the direct acting compressor of the American type. 

Another form of European compressor on the straight line plan is shown 
in Fig. 21. This machine is made by Messrs. Burckhardt & Co., Basel, Switzer- 
land. The steam and air cylinders are widely separated and are connected by a 
single piston reel joined at or near its centre by a crosshead, to which the con- 
necting rod is attached. 

Fig. 22 illustrates a type of straight line compressor of the larger sizes. 
The following are the specifications on which these machines are built : 

Cylinders. — Steam Cylinder, 14 inches in diameter, by 18 inch stroke. Air 
Cylinder, 1414: inches in diameter, by 18 inch stroke. Cylinders made of the 



PRODUCTION. 



57 



best cast iron suitable for this purpose, and of proper strength and thickness for 
carrjdng lOO pounds pressure, after being re-bored once. 

Water Jacket. — Air Cylinder and heads provided with Water Jackets. 

Bed Plate. — Bed Plate of the Box Girder type, made in a single casting. 
The bed plate to extend throughout the compressor connecting both cylinders 
and all parts, and strong enough to withstand the severest strain of air com- 
pressing work. 

Bearings. — Bearings to form an integral part of the bed plate, provided 
with removable bronze boxes, adjustable, accurately bored, and scraped to a 
true bearing surface. 

Shaft. — Main Shaft of hammered steel, 6 inches diameter in the bearings, 
turned, finished and key-seated, and free from flaws or other imperfections. 

Fly Wheels. — Two square rim Fly Wheels, 6 ft. o in. in diameter, with 
face and edges nicely turned and hubs bored and key-seated to fit shaft. The 
wheels to weigh when finished not less than 3,125 pounds. 




Fig. 22. 

Crank. — Crank pins of best hammered steel and securely fastened in fly 
wheels, and fly wheels counterbalanced. 

"■ Valve Gear. — Valve Gear of the slide valve type, with Meyer adjustable 
cut off gear. 

Piston Rod. — Piston Rods to extend through back head of steam cylinder 
and front head of air cylinder, and securely fastened in cross-head. 

Cross-head. — Cross-head of cast steel and amply strong, provided with 
bronze shoes, and with adjustment for piston rods. 

Material Used. — Piston Rods, Valve Rods, Connecting Rods and Crank 
Pins, of the best forged steel. Boxes for crank and cross-head pins of com- 
position metal. 



5« 



PRODUCTION. 



Throttle Valve. — Steam Cylinder provided with a Globe Throttle Valve, 
with flanges and hand wheel turned and polished. Valve provided with drain 
connection. 

Governor. — The Compressor is provided with an Automatic Pressure 
Regulator and unloading device. 

Indicator Connection. — Provision made on both steam and air cylinders 
for Indicator connections. 

Oiling Devices. — Oil Cups for all wearing parts ; one sight feed Lubri- 
cator for steam cylinder, one IngersoU-Sergeant Lubricator for air cylinder. All 
oiling devices extra large. 

Weight. — Total weight of Compressor ready for shipment, 10,800 pounds. 



^^S 




Fig. 23. — Compound Air Compressor. 



Arrows on the water pipes show the direction of water circulation. When 
pistons move as indicated by the arrow on the piston rod, steam and air circulate 
in direction shown by arrows in the cylinders. 

A — Inlet Conduit for Cold Air. 

B — Removable Hoods of Wood. 

C— Inlet Valve. 

D — Intake Cylinder. 

E — Discharge Valve. 

F — Intercooler. 

G — Compressing Cylinder. 

H — Discharge Air Pipe. 

J — Steam Cylinder. 

K — Steam Pipe. 

L — Exhaust Steam Pipe. 

N — Swivel Connection for Cross-head. 



PRODUCTION. 59 

O — Air Relief Valve, to effect easy starting after stopping with all pres- 
sure on the pipes. 

I — Cold Water Pipe to Cooling Jacket. 

2 and 3 — Water Pipe. 

4 — ^Water Overflow or Discharge. 

5 — Stone on end of Foundation. 

6 — Foundation. 

7 — Space to get at underside of Cylinder. 

8 — Floor line. 

Where larger volumes of air are required the direct acting type gives place 
to the compound and duplex. It is not considered good practice to build single 
compressors with air cylinders larger than 26 inches in diameter except where 
the air is compounded. 

Fig. 23 illustrates a popular type of Direct Acting Compound Compressor. 
The merits of this compressor are referred to by the manufacturers as follows : 

"The large air cylinder on the left determines the capacity of the Com- 
pressor, and for the illustration we have taken its piston at 100 square inches 
area. The small air C3dinder in the center can have an area of 33 1-3 square 
inches. The small piston only encounters the heaviest pressure, and at 100 lbs. 
pressure the resistance to its advance is 3,333 lbs. The resistance against the 
large piston is its area multiplied by the pressure which is caused by forcing the 
air from the large cylinder into the smaller cylinder, which is in this case 30 
lbs. per square inch. But as this 30 lbs. pressure acts on the back of the small 
piston and hence assists the machine, the net resistance of forcing the air from 
the large into the small cylinder is equal to the difference of the area of the two 
pistons multiplied by the 30 lbs, pressure. This is 66 2-3 by 30, and equals i,999 
lbs. Hence, 1,999 ^bs., the resistance to forcing the air from the large into the 
smaller cylinder plus 3,333 lbs., the resistance in the smaller eylinder to com- 
pressing it to 100 lbs., is the sum of all the resistances in the compound cylinders 
at the time of greatest effort. This is 5,333 lbs. The time of greatest effort is at 
the end of the stroke, or when the engine is passing the center. In the single 
machine this resistance is 10,000 lbs., hence we see that in the compound machine 
the maximum strains are less by over 46 per cent., or nearly one-half. By thus 
reducing the work to be done at the end of the stroke, more work is done in the 
first part of the stroke, and the resistance is made nearly uniform for the whole 
stroke. 

"The next step is to render the application of power also uniform for the 
whole stroke. This is accomplished in a very simple and effective manner. The 
steam and air pistons and crosshead are mounted on the same piston rod. These 
parts are purposely given weight enough so that it .requires most of the power 
of the steam over and above the air resistance at the beginning of the stroke to 
start them forward at the required speed. At the end of the stroke, when the 
steam has become weak by expansion, the power stored up in the momentum of 
these reciprocating parts is given out in useful work, and the parts are brought 
to a state of rest by expending their force upon the air in the compressing cyl- 
inders. As the energy which can thus be stored and given out by the reciprocat- 
ing parts depends upon their weight, and the square of the number of revolu- 



6o 



PRODUCTION. 



tions, it is evident that rotative speed is the most important factor. Hence very- 
long strokes are not desirable, because at the same piston speed the machines 
make fewer revolutions than machines of shorter strokes. Therefore, the power 
is not applied to the work so uniformly, and greater strains are brought on 
shafts, connecting rods and other parts, and larger fly-wheels, and frequently 
double engines, are necessary for successful operation, especially when steam 




is to be used expansively. The value of rotative speed for economical steam 
consumption is too well known to need reviewing here. It is of interest, how- 
ever, to note that the quick rotation that is valuable for applying the power uni- 
formly also contributes to steam economy. 

"Uniform resistance and uniform power both applied, as in this com- 
pressor, as direct end thrust and pull upon a straight steel piston rod, do not 
leave much work for fly-wheels to perform. Their presence, however, is neces- 



PRODUCTION. 6i 

sary to regulate the steam valve motions, to control the length of stroke, to even 
up and balance trifling inequalities of power and resistance and to secure a uni- 
form speed to the machine." 

Figure 24 illustrates a common type of Duplex Compressor where the 
steam end is of simple construction, provided with the Meyer valve gear, the 
cut-ofif being adjusted by a hand wheel while the machine is in motion. The 
point of cut-off is indicated by a pointer which moves over a graduated scale. 
The machine is run with a wide open throttle, being controlled entirely by the 
cut-off, which is proportioned in accordance with the steam and air pressures. 
An ordinary ball governor is used to regulate the speed of the engine and to 
prevent it from running away in case of breakage of air pipes or sudden loss 
of pressure. Attached to the ball governor manufacturers usually add a pres 
sure governor or regulator which is used to reduce the speed when the air pres- 
sure reaches the maximum. Various types of frames are used, some of them of 
the Corliss pattern; but for the purpose of insuring stability, freedom from 
breakage, and to resist the sudden strains which are brought to bear during com- 
pression, the frames, bearings and fly wheel are usually heavy. The steam and 
air pistons are in some patterns tied together by a heavy cast iron sole plate and 
tie rod. The bearings are usually of phosphor bronze, are unusually broad, and 
are provided with means for taking up wear. The cranks are usually made of 
wrought iron, and the crank pins, crosshead pin, piston rods, shafts, valve rods, 
links and pins, and all wearing parts, are of steel, and when possible this is 
hardened and ground. The heavy fly wheel gives a smooth, uniform motion, 
and aids in steam economy, by admitting of early cut-off. When running one 
side of the compressor at a time, the fly wheel prevents irregularity of motion. 
In this type of compressor the air cylinders are usually fitted with poppet valves, 
although manufacturers have succeeded in so far perfecting the positive moved 
valve and the piston inlet that they are applied with economy to the Meyer Du- 
plex machines. The air cylinder is sometimes made of hard brass, owing to the 
better conductivity of this material, and is as thin as can be made with safety. 
The cylinders of some machines are provided with jackets for water circulation, 
and the piston and piston rods are hollow. A telescopic water tube is intro- 
duced at the back end of the cylinder, and cold Avater is supplied to aid in keep- 
ing down the temperature during compression. The introduction of cold watei 
in this way undoubtedly reduces the heat of compression, but it is subject to the 
many disadvantages found in water injection. The water, unless free trom 
foreign matter, is liable to destroy the cylinder, and even when pure it is difficult 
to lubricate the parts, the water itself being a bad lubricant. This applies to 
that type where the water passes through the piston and in contact with the walls 
of the cylinder between the rings and completely around the piston. It is ob- 
vious that this leaves a thin coating of moisture in contact with compressed air 
which is at a temperature much higher than that of the water ; and as the voluinc 
of air is so much greater in proportion than that of the water, the result is an 
absorption of the water, which goes off into the air receiver in the form of 
moisture, to be afterwards deposited in the pipes when the temperature of the 
compressed air is reduced in transmission. It is claimed by the makers that one 
of their Duplex Meyer Cut-off Compressors was used and tested at Shaft No. 13 



62 



PRODUCTION. 



on the New York Aqueduct by Prof. James E. Denton, of Stevens Institute of 
Technology, and that it produced, a horse power with a consumption of 25 pounds 
of steam per horse power per hour. 

A duplex compressor can be regulated so as to run at high or low speeds. 
It may even stop and start automatically. Where the air is used intermittently — 
that is, where the use is irregular — a governor is furnished which will adjust 
the machine to a slow speed when little air is being used, stop when no air is 
required, and start again when necessary, thus using the steam only in propor- 
tion as the work is done. 




Fig. 2- 



The following are specifications of a type of Duplex Meyer Cut-off Valve 
Compressor : 

Cylinders. — 2 Steam Cylinders, 14 inches diameter, by 18 in. stroke. 

Two Air cylinders, 1454 inches diameter, by 18 in, stroke. 

Cylinders made of the best cast iron suitable for this purpose, and of suf- 
ficient thickness to safely carry ico pounds pressure after re-boring once. 

Piston Inlet. — Air cylinders of the Piston Inlet type. 

Water Jacket. — Air cylinders and heads provided with water jackets, 



PRODUCTION. 63 

Frame. — Frames of the Corliss Girder type, and strong enough to. with- 
stand the severest strain of air compressing work. 

Bearings. — Main pillow blocks provided with removable shell boxes of 
best composition metal, accurately bored and scraped to a true bearing surface. 

Shaft. — Main shaft of hammered steel, 6 inches in diameter in the bear- 
ings, and 7 inches in the center, of proper length, turned finished and key- 
seated, and free from flaws or other imperfections. 

Cranks. — Cranks of the disc pattern, of selected charcoal iron, and of 
ample strength and proportion for the work required. 

Fly Wheel. — One square rim fly wheel, 8 feet in diameter, with hub bored 
and key-seated to fit shaft. The wheel when finished to weigh not less than 
4.500 pounds. 

Valve Ge.\r. — Valve gear of the slide valve type, with Meyer adjustable 
cut-off. 

Piston Rods. — Piston rods extended through back head of steam cylinders, 
and attached by means of couplings to piston rods of air cylinders. 

Tie Rods. — Air cylinders securely fastened to steam cylinders with tie 
rods. 

Governor. — A fly ball governor of approved pattern placed in main steam 
pipe, and driven with belt from main shaft. 

Lagging. — Steam cylinders covered with polished black walnut. Space 
between lagging and cylinder to be filled with mineral wool. 

Material Used. — Piston Rods, Eccentric Rods, Connecting Rods, Crank 
Pins, Cross-head Pins and Valve Rods of the best forged steel. Boxes for main 
crank pins of best composition metal. 

Throttle Valve.— Both steam cylinders provided with a throttle valve, 
with flanges and hand wheel turned and polished. 

Indicator Connection. — Provision made on both steam and air cylinders 
for indicator connections. 

Oiling Devices. — Graduating sight feed oil cups for all wearing parts ; 
one sight feed lubricator for each steam cylinder; one Ingersoll-Sergeant lubri- 
cator for each air cylinder. 

Weight. — Total weight of compressor ready for shipment, 22,500 pounds. 

Figure 25 represents a type of Vertical Compressor which consists of a 
sicam engine connected by means of a crank shaft with two single-acting air 
pumps, all placed in an upright position. It is compactly built, and is as eco- 
nomical as this type of machine will admit. The cranks are so placed in rela- 
tion to each other that the greatest power of the engine is applied at the time of 
greatest resistance in the air cylinders. Water injection is usually applied to 
tlicse machines, and it is a matter of note that it is in this compressor that water 
injcclion has had its longest service, and has given its best results. One reason 
for this may 1)c found in the fact that the cylinders being placed vertically, arc 
not sul)jcct to the wear and destruction which accompanies water injection ma- 
chines of the horizontal tyi)C. This compressor has been largely used in the 
western part of the United States for mining service, though of recent years, 
notably at the Anaconda Copper Mines, it has been replaced by machines of a 



J 



64 PRODUCTION. - - -. . 

more improved and more economical type on the pattern of the Duplex Corliss 
Compound. 

A type of vertical air compressor used in Europe, known as the "Cham- 
pion," has both the inlet and the outlet valves with their seats arranged in the 
cylinder covers ; the form of the frame is such that the valves can be readily 
moved without disturbing the cylinder cover joints. The inlet and outlet valves 
are provided with very long guides to insure their continued working without 
damage, and being placed vertically, the wear is more evenly distributed. The 
air cylinder and outlet valve boxes are surrounded by cold water jackets. 

The experience of American mafiufacturers, which has been more ex- 
tensive than that of others, has proved the value of direct compression as dis- 
tinguished from indirect, as shown clearly in this type of machine. By direct 
compression is meant the application of power to resistance through a single 
straight rod. The steam and air cylinders are placed tandem. Such machines 
naturally show a low friction loss, because of the direct applicatiou of the power 
to the resistance. This friction loss has been recorded as low as 5 per cent., 
while the best practice is about 10 per cent, with the type which conveys the 
power through the angle of a crank shaft to a cylinder connected to the shaft 
through an additional rod. w. l. saunders. 



Editor Compressed Air: 

Dear Sir: 

Having been greatly interested in your series of articles on the <ievelopnient 
of the air compressor, I beg leave to call your attention to a few points in the 
article in the November number of your paper. 

In the abstract of Mr. Darlington's test, the figures show an efficiency of 
compressions of 98.4% (tIfM) which is scarcely credible, as the resistance of 
the outlet valves alone will generallly cause a greater loss than this. 

It is a well known fact that indicator springs are temporarily weakened by 
heat and they are therefore adjusted under steam. As an instance of this fact, 
I recently tested a spring under steam pressure and found the scale to be 32.6. 
On allowing the indicator and testing drum to cool and then admitting com- 
pressed air, the scale was found to be 34. These figures were verified by three 
separate trials, the scale of the spring varying slightly at different pressures as 
is always found, but the comparative results remaining the same. 

If Mr. Darlington did not calibrate his air compressor indicator springs 
with air, and his engine indicator springs with steam, his results are liable to an 
error of fully five per cent., and this error is in all probability the cause of the 
high efficiency of compression and the low efficiency of mechanism. 

Further on the article reads as follows : "Hydraulic piston compressors are 
oubject to the laws that govern piston pumps and are therefore limited to a piston 
speed of about 100 feet per minute. It is quite out of the question to run them at 
much higher speed than this without shock to the engine and fluctuations of air 
pressure." * * ♦ 



PRODUCTION. 65 

In the first place, modern practice for "piston pumps" of a size to be com- 
pared with air compressors is 250 feet per minute (see "Kent," page 605). I 
have lately seen a pump running at a piston speed of 300 feet a minute against 
a water pressure of 325 pounds, and have taken indicator cards from this pump 
showing entire absence of injurious shock. 

Also any one can see in this country at a mine, the name of which I am 
not at liberty to mention, fully a thousand horse-power of hydraulic plunger com- 
pressors running at a piston speed of between 230 and 250 feet per minute, and 
running day and night, year in and year out, and the indicator cards are excep- 
tionally good. Yours truly, Charles P. Paulding. 



Editor Compressed Air: 

I. — If I compress air to 150 lbs. per inch in reservoir No. i, and then 
cool it down with water to 35° f. h., and then recompress it to 200 lbs,, and then 
expand it in my refrigerator, will it produce a greater degree of cold in the 
refrigerator than it would if I had compressed it to 200 lbs. in the first place and 
cooled it to 35°? 

2. — What pressure do the street cars carry in your town ? 

3. — Is there any trouble with freezing of the valvies in small compressed air 
engines? 

4. — If compressed air is left a long while in a tight reservoir does it lose 
any of its expansion force? 

5. — Will the compressing cylinder get red hot if it has no water jacket? 

6. — What per cent, of loss is there from the steam engine to the air motor, 
or how much less energy is there at the motor than at the engine that supplies 
the air? 

7.; — How many volumes of air have to be compressed into one to get 50 
lbs. to the square inch? 

8. — How high can water be raised with economy with air? 

9. — Is it cheaper than pumps for a long lift? 

10. — Does the higher pressure produce the most cold when expanded? 

II. — Will an engine give as much power with air as steam at the same 
boiler pressure? 

Please answer and oblige, J. S. Sherman. 

I. — No; the temperature at end of expansion depends upon the initial tem- 
perature and the number of expansions. In both cases you have the same initial 
pressure in your motor, and therefore can produce the same degree of expansion. 

2. — Storage pressure of 2,000 lbs. per square inch, and a working pressure 
ranging from 130 to 150 lbs. 

3. — All trouble can be avoided by enlarging the exhaust opening. If the 
air is reheated before admission to motor, a low temperature at exhaust will be 
avoided and the efficiency will be increased (see Compressed Air, p. 71, No. 5). 

4. — No. 

5. — No; the theoretical temperature at end of compression without cooling 
KT 60 lbs. gauge pressure, is 382° F. 



66 PRODUCTION. 

6. — See articles in Compressed Air, page 89, No. 6, and page 13, No. 4, 
for full discussion on this point. 

7. — ^4.4 volumes, for equal temperature compression. 

8. — The highest practical lift made at present is 200 feet. Cases of still 
greater lift are on record. 

9. — The Pohle air lift compares very favorably in economy with the direct 
acting pump. 

10. — The higher the pressure the greater the expansion, and therefore the 
lower the temperature. 

II. — If you mean that the initial pressure in the motor is to be the same 
in each case, and the air is to be used without reheating, then the steam will be 
more efficient as a fluid. 



GROWING INTEREST IN COMPRESSED AIR. 

An evidence of the growing interest taken in compressed air was noticed 
at the recent monthly meeting of the New York Railroad Club, held in the rooms 
of the American Society of Mechanical Engineers in New York City. A paper 
was presented at that meeting by Mr. Shields, in which compressed air and its 
application to railroad shops was discussed. The attendance at the meeting was 
exceptionally large; perhaps the largest held since the organization of the Club. 
The discussion of the subject was so general that it was found necessary to close 
the meeting on account of the lateness of the hour, before the subject had been 
exhausted. It is likely that there will be a continuation of the discussion at a 
subsequent meeting. 

Railroads have been quite active of late in developing compressed air ap- 
paratus. There is no particular reason why railroad shops should use compressed 
air to any better advantage than machine shops and foundries in general. If 
compressed air is a good thing in railroad shops, the same reasons that make 
it so apply to other shops. That it is a good thing, and that its use 
is growing, no one doubts. Its advantages and the saving that is effected by its 
use are now established facts. Some of the figures representing this saving were 
given at the meeting. In looking for the reasons why railroads have been 
pioneers in this line, we turn to the air pump used on locomotives. This pump, 
or compressor, had done such good work for years, and has become so familiar 
to the master mechanic that it turned attention to compressed air power. The 
simplicity of the apparatus, the ease with which it was cared for and understood 
by mechanics, and the apparent applicability of the air to so many different pur- 
poses, led to developments in this line. 

An old locomotive sent to the shop for repairs was immediately robbed of 
its air pump, which was bolted against the wall of the shop and put into use, 
serving a useful purpose in helping to repair the engine. Shops in this way be- 
came equipped with a number of air pumps, until it was apparent that an air com- 
pressor properly designed for economic production of compressed air should have 
a permanent place in the establishment. 



PRODUCTION. 67 

All this bears out the view which we have always taken of this subject; 
that is, that the use of compressed air has not grown as rapidly as it should, 
because it is not understood. It is looked upon as too much of a mystery, and 
the idea has existed in the minds of men that at best it is an expensive power 
to produce. A little experience with it convinces the most incredulous that it 
is not an expensive power either to produce or use, nor is its use dangerous 
as some suppose; on the contrary, there is no power so humane. There is 
certainly nothing explosive about air itself. When confined in a weak vessel it 
may create a disturbance, but there is no occasion for the use of weak vessels 
in either steam or compressed air. It is evident that an explosion in a steam 
vessel is more likely to produce hurtful results than if the same vessel were 
filled with air. Not only is the scalding effect from steam objectionable, but there 
is usually a confined body of superheated water held down by the steam and 
always ready to expand into hot steam globules as soon as there is a release of 
pressure. This means a large reserve force which under usual conditions sur- 
rounding explosions will result in a damage more serious than any likely to occur 
or hardly possible with compressed air. 



COMPRESSED AIR : ITS PRODUCTION, TRANSMISSION AND USE.* 

Air being such a common subject, requires no Introduction. Compressed 
air is simply air under pressure, or air increased in density by pressure or by 
heat. It is one of the oldest of the sciences, although in its general application 
one of the youngest, for it is only within the last thirty or forty years that com- 
pressed air has been used for mining and tunneling, for which no other power 
was available, and in fact in all the early uses of compressed air, it was only 
used where it was considered a necessity regardless of expense, it having always 
been termed an expensive power. It is true that it takes work to compress air. 
although the writer has heard of instances where contractors, when the com- 
pressor first became known, wanted to run drills on open rock work with com- 
pressed air, thinking they would thereby abandon their boiler plant and save 
buying coal, their idea of a compressor being a machine which would furnish air 
without using power, or, in other words, a modified form of perpetual motion. 
It is also true that there are losses in the compression and use of air to which 
no attention was paid in the earlier machines, and which exist in many plants 
to-day, where, however, the great convenience of the air and its saving in many 
other ways more than make up for the loss due to the compressor. 

The one great loss in the compression of air is due to the heat caused by 
compression and the consequent increase in the volume of the air. The minor 
losses are clearance in the air cylinder, the heating of the intake air in passing 
through the valves, and the friction of the compressor. The first two of these 
iniount to very little, and arc hardly noticeable in a good machine. The last 



An AddreHQ dflivered a( Lafayette Collfj^e, EaKtoii, Pu., I)y Mr. William V 



68 



PRODUCTION. 



loss mentioned, friction, amounts to from 7 to 15 per cent., depending to a great 
extent on the amount of care that is taken with the machine. To clearly illus- 
trate the work that is done in an air cylinder, we have recourse to the indi- 
cator, and the following diagram, Fig. 26, shows an indicator card taken from a 
water jacketed air cylinder (the card having the isothermal and adiabatic lines 
plotted on same), an examination of which gives us the actual results obtained. 

Referring to Fig. 26, we have the adiabatic or heat line A-B, which repre- 
sents the work done if there were no cooling effect in the cylinder, the line A-C 
representing the actual work done in the cylinder, and the isothermal or con- 
stant temperature line A-D, which is the line the indicator would make if all the 
heat generated could be carried off during the work of compression. 

This latter condition does not exist in our high speed machines of to-day, 
but one can imagine it to exist in a machine where the piston travels slow 
enough that all the heat would be carried off by the water jacket or by radiation. 




Fig. 26. 



In following the movement of the piston in the cylinder, suppose it starts at A, 
the cylinder then being full of free air, and moves to the right, the pressure in 
the cylinder at any point is represented on line A-C. When the piston reaches 
C, it has compressed the air to the receiver pressure and it must then push the 
compressed air out through the discharge valves into the receiver. Owing to the 
weight of the discharge valves and the tension of the springs holding them to 
their seats, the pressure in the cylinder reaches a few pounds above the re- 
ceiver pressure before the valves open, as shown at E, and there gradually drops 
to the receiver pressure at the end of stroke, the irregularities in the line being 
due to the fluttering of the discharge valves and the vibration of the indicator 
arm. 

The piston having reached the end of stroke, comes to a standstill while the 
crank is passing the dead "center, and as the current of air that held the discharge 
valves open in passing out of the cylinder has ceased, the discharge valves close 
by the tension of the springs back of them. The piston now starts to recede — the 
air under pressure that was left in the cylinder due to the clearance space ex- 



PRODUCTION. 69 

panding until it becomes atmospheric pressure at F, when the inlet valves open 
and the cylinder is filled with free air. If the indicator line follows along the 
atmospheric line, we know that the inlet area is not restricted and we are get- 
ting a volume of free air at atmospheric pressure represented by the travel of pis- 
ton from F to A, this representing the actual free air capacity of the machine. 
The volume between G and F representing the air contained in the clearance 
space, expanded, is lost as far as the capacity of the machine is considered; and 
although this air required work in compressing it to 75 lbs. pressure, it has 
given out its work in expanding, helping to compress the air on the other side 
of the piston. 

The only loss in work due to the clearance space is that resulting from 
the small amount of cooling that the confined air has been subjected to, its 
volume when hot having been a trifle more and having required more work to 
compress it, but this is rarely taken into account. We thus see that the clearance 
space in the cylinder is not a loss of power, but a loss of capacity, which is al- 
lowed for by deducting anywhere from 3 to 10 per cent, of the cylinder volume, 
according to the design of the air cylinder and the length of stroke of same — it 
being evident that the longer the stroke for the same size cylinder the less will 
be the percentage of clearance. On some indicator cards it is noticed that the 
intake air pressure falls below the atmospheric line, showing that the air inlet 
is restricted, or, as is common on air cylinders having poppet inlet valves closed 
by a spring, the tension of the spring when the piston is moving slow at the end 
of the stroke, will close the valves before the piston has completed its stroke, so 
that when the end of stroke is reached a partial vacuum is formed in the cylinder. 
Where these defects exist, the piston must travel a distance as A-0 before the 
atmospheric line is reached, and the volume of the cylinder would be 0-F, in- 
stead of A-F, making the 10 per cent, allowance for clearance necessary, while 3 
to 4 per cent, should be sufficient on a well designed machine. 

The temperature of the air at 75 lbs. gauge pressure without' any cooling 
is 419 degrees, although this is somewhat lower in the cylinder, due to the 
jacket cooling; and from actual readings on thermometers placed in the dis- 
charge pipe close to the cylinder, the temperature is from 300 to 360 degrees, ac- 
cording to the size and speed of the machine. 

Referring again to Fig. 26, we have the volume C-K-N-G, representing 
about 25 per cent, of the free air volume at, say, 340 degrees temperature, to put 
into the receiver at each stroke of the machine. As the receiver is anywhere 
from ID to 20 ft. from the compressor, and as it has a large surface exposed for 
radiation, its temperature will be considerably less than that of the air leaving 
the cylinder, which will consequently be cooled and reduced in volume, and as 
the air is generally used a considerable distance from the compressor, it will have 
reached atmospheric temperature by the time it is used and our original volume 
C-K-N-G, when leaving the cylinder, will have shrunk to D-K-L-G by the time 
it was used, being then only 16-25 oi what we would have had had the air been 
used hot directly as it left the compressor. 

This shows us clearly the two most important factors where a large sav- 
ing can be effected in the production and the use of air — the first being to cool 
the air as much as possible during compression, and the second to heat the air 



70 



PRODUCTION. 



as much as possible before using; and although the above diagram represents 
the actual conditions of many of the small compressor plants in existence in 
which the air is used as explained, these losses can be and are successfully over- 
come in most of our large compressor plants of to-day where air is being pro- 
duced and used, with a less expenditure of coal than if steam were used direct, 
leaving all the saving by the use of the air as a clear gain for the operators. 

Turning our attention now to the main factor for the economical com- 
pression of air, which is to cool it as much as possible during compression, we 
having the following styles of compressors for the accomplishment of same, 
namely: the wet compressors or those in which water is used in the cylinders; 
the dry or water- jacketed compressors, and the compound or stage compressor, 
where the work of compression is done in two or more cylinders, the air being 
cooled in passing from one to the other. 

Of the first named style there are two forms, one being that in which the 
water is let into the cylinder with the incoming air, and the other in which the 




Fig. 2/ 



water is injected into the cylinder in the form of a spray while the air is being 
compressed. In the first form there is a great deal of water in the cylinder, 
which then very much resembles a pump, but as the air and water do not become 
mixed, the air is but very little cooled, while the water, on the other hand, reduces 
the efficiency of the machine by the increased friction in the cylinder and the 
slower speed that the compressor must be run at. The water injection machine, 
on the other hand, is the best known way of cooling the air in a single cylinder, 
but as it still retains all the disadvantages of having water in the cylinder, caus- 
ing often the rapid wearing of the parts, all of the American compressors of to- 
day are made with water jacketed cylinders, the loss in economy being more than 
counterbalanced by having a machine which will not require the constant renewal 
of parts. 

In designing an air cylinder, the object is to get as much of the body of 
the cylinder and heads jacketed as possible, the heads in particular being the 



PRODUCTION. 71 

most effective, a^ they are exposed to the air during the entire length of stroke, 
while the body siirface diminishes as the piston travels toward the head. The 
smaller the air cylinder the more effective is the jacket, for in cylinders of dif- 
ferent diameters the volume of air they contain is proportional to the square of 
their diameter, while the cooling surface is in the direct ratio of the diameter; 
that is, if one cylinder were twice the diameter of the other, it would hold four 
times the volume of air and only have about twice the cooling surface, being 
thus only one-half as efficient as the small cylinder. Compressors have been 
built where the air cylinder proper was made up of a great number of small 
cylinders all enclosed in water, and they have given very economical results, 
but they are expensive to build and very liable to get out of order owing to the 
large number of small valves required for the many cylinders. 

The most economical way of compressing air is by doing it in stages; 
that is, using two or more cylinders, compressing it to a low pressure in the 
first, then passing it through a cooler cooling it to atmospheric temperature and 
then further compressing it to a higher pressure, cooling it and compressing it 
again, and so on, depending on the pressure required, the two-stage or com- 
pound compressor being used for pressures between 60 and 300 lbs., the three- 
stage or triple compression between 300 and i,0G0 lbs., and the four-stage or 
six-stage between 1,000 and 3,000 lbs., or higher. 

We have in Fig. 27 a combined indicator card of a compound compressor, 
in which A-B is the adiabatic, A-D the isothermal, and A-F-E-C the line show- 
ing the actual work done in the cylinder. The low pressure card is represented 
by A-F-J-K, the pressure reached in same being governed by the size of the 
high pressure cylinder and the efficiency of the intercooler. The distance, H-M, 
represents the volume of the high pressure cylinder in proportion to the low 
pressure cylinder represented by H-A, the diagram showing that the compres- 
sion line in the high pressure cylinder starts at the isothermal line, showing that 
the air was cooled to atmospheric temperature before entering the high pressure 
cylinder. 

The compressed air leaving the low pressure cylinder is represented by 
F-J-H-L, and passing through the cooler it shrunk in volume to E-J-H-M, rep- 
resenting the size of the high pressure cylinder. Had the cooler not been per- 
fect, the air would have retained part of its heat, keeping its volume consequently 
larger, and a higher pressure would have been necessary in the low pressure 
cylinder, the card then being as shown by the dash-dotted line representing more 
work done in the cylinder. This shows the necessity of having a perfect cooler, 
the important part of which is that the air is broken into thin sheets so that it 
can be easily cooled- The air and water should also travel in opposite directions, 
so that the air in leaving the cooler meets the coldest water, and the cooler 
should also hold a sufficient volume of air so that there will be no drop in the 
intake air pressure of the high pressure cylinder. 

Comparing the compound cylinder card, Fig. 27 with Fig. 26, it is seen that 
the amount of work represented by F-B-C-E has been saved, amounting to about 
14 per cent, of the total work, or where it took 16 h. p. to compress 100 cu. ft. 
of free air to 75 lbs. in a single cylinder, a compound cylinder would use 13^. 
Where air is to be compressed to higher pressures, the saving in compounding 



72 



PRODUCTION. 



becomes more marked — 500 lbs. pressure requiring 40 11. P. for compressing lOO 
cu. ft. of free air in a single cylinder, and 30 h. p. in a compound cylinder, or a 
saving of 25 per cent., this percentage increasing with higher pressures, and at 
2,000 lbs. using four cylinders for doing the work, the work saved over a single 
cylinder is 45 per cent. 

As the object is to cool the air as much as possible during compression, 
the colder the air is to start with the better; thus a considerable saving can be 
effected by taking the air supply from as cold a place as possible, carrying the air 
through a wooden box to the compressor. Approximately for every 5 degrees 
that the intake air is colder than the air in the engine room, a saving of one per 
cent, is effected in the running of the machine ; and as there are many days in the 
winter months where there is a difference of 50 degrees between the tempera- 
ture indoors and outside, a saving of 10 per cent, can be effected by supplying 
the compressor with the cold air from outdoors, instead of using the hot air of 
the engine room. Using cold air increases the capacity of the machine, a dif- 
ference of 50 degrees in the air used amounting to about 10 per cent, increase 
in the amount of air the compressor will deliver. 

We have so far in our figures been dealing with compressed air at sea 
level where the atmosphere has a pressure of 14 7-10 lbs. At higher altitudes the 
atmosphere is more rarefied, representing less pressure per square inch, as shown 
by the following table : 

PRESSURE. 

At % mile above sea level — 14.2 lbs. per sq. inch. 



" H " 




—13-33 


« 


<( « 


" Va " 




—12.66 


t^ 


<c a 


" I 




" — 12.02 


e( 


ti ( 


" iYa " 




' — 11.42 


a 


(( I 


" IH " 




—10.88 


" 


u t 


a 2 <' 




— 9-88 


11 


i( ( 



Or an approximate reduction of ^ lb. per square inch for every i.ooo feet of 
ascent. Owing to the rarefied condition of the air at high altitudes it is evident 
that when this air is compressed its volume under pressure will be considerably 
less than if the same volume of free air at sea level pressure had been com- 
pressed to the sami pressure. 

According to Mariotte's law, the pressure of any gas varies in the inverse 
ratio of the volume, the temperature remaining constant, or the volume of a 
given quantity of gas is inversely as the pressure it supports ; or representing 

P' as being the absolute pressure at any point of the stroke, 

P the original absolute pressure, 



r 



PRODUCTION. 73 



V the volume corresponding to the required point of the stroke, 
we have for the pressure at any point of the stroke, 

P 

P' = ~ 
V 

or for the volume at any point of stroke — 

P 

V = — 

P' 

Remembering that in all computations absolute pressures (pressures above 
vacuum) are to be taken, and not gauge pressures; remembering also that the 
results obtained will be in absolute pressures from which the atmospheric pres- 
sure must be deducted to obtain the gauge pressure. Applying Mariotte's law 
in determining the difference in volume by compressing at sea level or at an 
altitude, suppose we compress one cubic foot of free air at the sea level to 75 
lbs. gauge pressure, which equals 90 lbs. absolute pressure, we have by Mariotte's 
law — 

P 15 

V = — or V = — 

P' 90 

Suppose we were compressing air at an altitude of one mile, where the pres- 
sure of the atmosphere, according to our table, is 12 lbs., we have by the same 
law — 

P 12 

V = — or V = — 

P' 87 

or only about 4-5 as much air as when at sea level. 

As many air compressors are now used at high altitudes, allowance is 
made for this loss by deducting a certain percentage; in the above case, 20 per 
cent, from the rated capacity of the machine, amounting to 7 per cent, at J4 ^^^ 
altitude, and increasing abouc 4 per cent, for each additional J4 ""^ile oi altitude, 
at two miles the loss being about 34 per cent. 

As the volume of air decreases, the required power of the compressor 
also decreases, but the capacity decreases in a greater ratio than the power neces- 
sary to compress, hence it follows thzlt operations at a high altitude are more 
expensive than at sea level. At io,ooO feet this extra expense amounts to over 
20 per cent. 

Having now given a general description of the work done in an air cyl- 
inder, I will briefly describe the construction of the air compressors that are in 
general use to-day. Probably the simplest and the best machine for a small 
plant is what is known as a straight line self-contained machine, in which the 
air and steam cylinders both in a direct line are fastened to a common bed-plate. 

Fig. 28 shows a steam and air indicator card taken from such a machine, 
from which it is seen that the greater part of the work in the steam cylinder is 
done at the beginning of the stroke, while in the air cylinder it is done at the 
latter part of the stroke. To make this possible where steam is to be used ex- 



k 



74 



PRODUCTION. 



pansively, as shown in the card, it is necessary to use heavy fly-wheels and re- 
ciprocating parts on the machine, the energy of the steam cylinder at the be- 
ginning of the stroke being stored in the fly-wheels, which in turn give up their 
energy in compressing the air at the end of the stroke. 

The question is often asked, How is it possible with the same size cyl- 
inders to get a higher air pressure than the steam pressure used? By referring* 
to Fig. 28, it will be seen that the steam card represents a higher mean effective 
pressure than the air card, showing that the steam cylinder has done the most 
work owing to the friction of the machine, although the air card shows the 
higher pressure. This is due to the energy of the steam cylinder being stored 
in the fly-wheels, and where the fly-wheels are made sufficiently large and heavy, 
no trouble is experienced in getting from 50 to 75 per cent, higher air pressure 
than the steam pressure used; this, however, being very poor steam economy, 











j^ieciTTt . \. 


/ ^«>* 




Jxr.E.I* S3,G 


^^y^ jyl.Jff.T. 00,S 




S— ,rrr 





Fig. 28. 



as it would be necessary to cut off late in the steam cylinder, utilizing very little 
of the expansive power of the steam. For good economy, working at about 80 
lbs. steam and air pressure, the cylinders should be about the same diameter, 
thus allowing from ^^ to ^ cut-off in the steam cylinder; or if higher air pres- 
sures are required, the size of the steam cylinder should be increased accordingly. 
It must not be understooa that a compressor cannot be built without a 
fly-wheel, for there are thousands of such in every-day use, by which I refer to 
the air pump used on every locomotive. It would not be fair to criticize this 
machine in connection with the duty it performs, for it has too well stood the 
test of years, its lightness and compactness being more valuable features than 
economy in the use of steam ; but commenting on the same, when used in a shop 
we have but to understand that for each stroke of the machine a full cylinder of 
steam is required at the maximum air pressure, comparing which with the fly- 
wheel compressor where steam is cut off at ^ stroke, shows that the air pump 
has used four times as much steam as the air compressor would have used for 
compressing the same amount of air. 



PRODUCTION. 75 



r 

^^^r Another form of wheelless machine is that in which the air cylinder at 
each stroke and after being filled with free air, is filled with air at receiver pres- 
sure by opening the discharge valve at *the beginning of stroke. The air cylinder 
now has a uniform maximum load for its entire stroke resembling the water 
cylinder of a pump, but this also necessitates a whole cylinder of steam at maxi- 
mum pressure to do the work. 

Attempts have been made on wheelless machines to use steam expansivly 
by making the reciprocating parts, noticeably the crosshead, of sufficient weight 
that their momentum would compress the air at the end of the stroke after the 
steam had been cut ofl^, but a machine of this kind can only be designed for a 
fixed speed and pressure, the weight being too heavy if run faster, and not of 
sufficient weight to do tl*e work if run slower, — making in all a poor substitute 
for a machine that is called upon to do a variable amojimt of work. From these 
accounts it is seen that the fly-wheel is really a necessary part for an economical 
compressor. 

The straight line compressor is made with many different arrangements 
of cylinders, the steam cylinders, air cylinders, or both, being compounded, but 
in all of these the work of the cylinders is in a direct line and the fly-wheel 
uses its stored up energy twice in each revolution to overcome the maximum 
load at the end of stroke. 

To more uniformly distribute the work during each revolution, the du- 
plex form of compressor has been adopted as the best type for the larger and 
better machines. This is essentially two straight line machines placed side by 
side with a common shaft for the two, the cranks of same being set at 90 per 
cent, to each other. This divides the work through four parts of the revolution, 
making the machine more uniform in its motion and allowing it to run slower 
and with better steam economy than a straight line machine, avoiding also all 
dead centers, so that the machine can be started up at any part of the stroke. 
The duplex compressor is also made with different arrangements of cylinders, 
the best types being those having cross compound steam and air cylinders. 

These two types of machines are to-day considered the standard; but as 
an air compressor is but a steam engine with an air cylinder attached, it has prob- 
ably been built in every form, whether horizontal or vertical, that a steam engine 
has ever been built. 

In determining the style of compressor best suited for the given duty, con- 
ditions such as the size of plant, cost of fuel, the length of time the plant will be 
used, cost of foundations and first cost of machine must be considered, for the 
higher the efficiency of a compressor the greater will be its first cost; but for a 
permanent plant no machine can be too good or too economical in its operation. 

As air is generally used under the same conditions and with the same 
machinery that uses steam, the true way of comparing the efficiency of a com- 
pressor would be to compare the volume of cold compressed air that the com- 
pressor will furnish with the volume of steam the compressor used at the same 
pressure to furnish the amount of air. 

Assuming it thus, the efficiency of a straight line compressor, non-com- 
pound, would be about 60 per cent. ; a duplex Corliss compressor non-com- 



76 PRODUCTION. 

pound, about 65 per cent., and a duplex Corliss compressor with compound con- 
densing steam and compound air cylinders with inter-cooler, about 90 per cent., 
or in the latter case we would have 90 per cent, as much cold air as steam that 
was used. If we consider for a moment the properties of compressed air as 
compare^ to steam, we find everything in favor of the air, as it remains ever 
ready to be used, regardless of the exposed condition of the pipes through which 
it passes, while steam, if carried around in uncovered pipes outdoors, condenses 
very fast, this condensation often amounting to from 15 to 30 per cent., so that 
if air was used under these conditions, it would be more economical than steam, 
without taking into consideration the great convenience of the air and the saving 
it effects in the increased running of the machinery, less friction, saving of hose 
and oil, and the ease with which all machinery and pifies can be handled owing 
to their being always cool. We have thus far only considered the use of air when 
in a cold condition, but far greater economy can be obtained by heating the air 
before using, as will be explained later on. 

We often read lengthy articles on the efficiency of an air compressor plant 
where the compressor and all the pumps and hoisting engines or machinery that 
used the air were carefully indicated and figured out, and they find that the work 
the air done in horse-power is only about one-third of the indicated horse-power 
of the compressor; or, in other words, that the compressor plant has only an 
efficiency of 33 per cent. This certainly looks very unfavorable for the use of 
compressed air, but it nevertheless is a condition which exists, the reason for the 
same being due to the very uneconomical machinery with which air is always 
used, and it is this uneconomical use of air which has done much to keep it from 
being more generally employed as a power. 

The above statement as to the efficiency of a plant is, however, misleading, 
unless one takes into consideration as to how the power is measured at the com- 
pressor and how the air is measured in being used. The indicated horse-power 
of the compressor is the amount of work done in compressing the air, using, how- 
ever, in an economical machine the full expansive power of the steam, or at the 
end of the stroke when the steam cylinder is ready to exhaust, no pressure, and 
consequently no work, is left in same. 

In the pumps, hoisting engines or drills using the air, we have, however, 
a different condition. Here the cylinders are filled full of air under pressure, 
and at the end of stroke, when the cylinders open to exhaust, the whole cylinder- 
full of air under pressure is allowed to escape into the atmosphere, utilizing none 
of the expansive power contained in same; in other words, the power is sup- 
plied or measured at the compressor when used in the most economical way, 
while the air is used in the most wasteful way, hence accounting for the poor 
showing; but it must be remembered that the machine which used the air would 
.use steam under the same wasteful conditions, and would show a correspondingly 
poor efficiency if compared with the same volume of steam used expansively in 
an economical engine. The amount of steam used to compress the air, if used 
direct in the pumps and hoists, would be but little more than enough to run the 
same, and the efficiency of the compressor plant would be from 60 to 90 per cent., 
according to the compressor, when compared with the volume of steam used, 
as against 33 per cent, when horse-powers are figured. Hence, as previously 



PRODUCTION. 77 

stated, the only intelligent way of making comparisons of the efficiency of the 
air system would be to compare volumes, and not horse-powers. 

TRANSMISSION OF AIR. 

Of the transmission of air, very little need be said, for it is simply carried 
around in pipes, the same as steam or water, but being more easily handled than 
either, for no matter what the length of pipe, there will be no condensation as with 
steam, and no shock as with water. As to the distance that air can be carried, that 
depends entirely on the volume of air and the size of pipe, the only loss being a 
reduced pressure at the end of pipe line, caused by friction if the pipe is not of 
sufficient size, but at this reduced pressure the air has a larger volume, so that the 
loss is not as much as the fall in pressure would make it appear. 

Air pipe lines have in different places been laid for distances of 15 miles 
or more, but the average pipe lines in tunnels and around quarries run from 1,000 
to 10,000 feet, for which conditions the pipes can generally be made large enough 
at a small expense, so that the friction will only amount to a few pounds loss of 
pressure. 

As a practical example of what would be required, if 1,000 cu. ft. of free 
air compressed per minute to 80 lbs. pressure, was to be carried a distance of 5,000 
feet, a 5-inch pipe line would show a loss of pressure of about 6 lbs., and a 6- 
inch pipe about 2j^ lbs., all elbows in the pipe line increasing the friction, so as 
few as possible should be used. The friction loss may be considered for ordinary 
purposes as being proportional to the length of pipe and as the square of the 
velocity of the air, twice the volume passing through the same size pipe, giving 
about four times the friction. 

A receiver should always be placed close to the compressor, to better 
equalize the work on same, answering also at the same time as a separator, taking 
much of the water and oil out of the air, these dropping to the bottom of the re- 
ceiver, where they are blown out at frequent intervals. A second receiver should 
be placed where the air is to be used, as the air being still further cooled will 
drop most of its moisture, which can be again blow^n out at the second receiver, 
leaving dry air to be used in the machine. All pockets in pipe lines should be 
avoided, as they have a tendency to hold water and thus retard the free passage 
of the air ; and wherever a machine is used at; the end of a long air pipe draining 
in the direction of same, provision should be made for blowing out the water be- 
fore using the air. Should it become necessary to pass air through a pipe line, 
which must of necessity have many pockets in same, so much water may be held 
in the pockets that very little air pressure would be gotten at the end of the line. 
Where these conditions exist, much trouble can be avoided by thoroughly cooling 
the air, thereby taking out all its moisture to a temperature lower than that of 
the pipe through which it will pass, so that the air will have a tendency to take 
up moisture in the pipe instead of dropping its water in same. By doing this the 
air pipe will always remain free, so that the full air pressure will be gotten at the 
end of the line. For carrying the air to cranes and hoists rubber hose has ad- 
mirably fulfilled the requirements, for with the use of quick-acting couplings or 
a line of hose wound on a drum, every convenience has been obtained. 



78 PRODUCTION. 

USE OF AIR. 

In the use of air, about the only objection that has been offered to the same 
is the freezing up of the exhaust. Whenever air is used expansively, it must 
draw its heat from the surrounding objects, and if any moisture remains in the 
air it will have a tendency to freeze the same. The freezing of the exhaust can 
be avoided by having the air perfectly dry before using, hence the object of the 
receivers and drains ; or if this is not possible, a small stream of water about the 
size of a needle in the exhaust will have the desired effect. As these preventives 
to frost, however, do not add any to the economy of the system, the only true way 
of overcoming all the tendency of the air to freeze is to reheat the same before 
using, getting back all of the work or the volume of the air that was lost in cool- 
ing while passing from the compressor to where it was to be used. This heating 
of the air is to-day successfully and economically accomplished, the heating of 
same increasing its volume from 35 to 50 per cent., this increase costing only 
about one-sixth the amount of coal in the heater that the compressor used for 
compressing an equal volume of air. 

Heaters in use to-day are made similar to a stove where the air in thin 
sheets passes over the heated sides of a jacket, or other forms are made where 
the air passes through hot water, both of these having been very successful in 
their application. 

When a compound condensing compressor, with compound air cylinders 
producing about 90 per cent, as much cold air as steam that was used, has the air 
reheated before it is used, we can easily see how the compressed air plant can 
claim to have an efficiency of about 20 per cent, more than if steam were used 
direct, regardless of the many other advantages and conveniences that are due 
to the air.. 



COMPRESSED AIR IN ENGLAND. 

This is a subject which has, during the past few years, been creating more 
genuine interest than some of the later discovered motive forces. 

It used to be said that we know but little of the possibilities of electricity, 
and one hears the same now being said concerning compressed air, but we are 
expecting something from it — something startling, on the lines of liquid air. 
What a triumph for air — compressed or liquid — if it could solve the perpetual^ 
motion problem, with surplus power to spare. We are looking to you in 
America for these new developments. It would be doubly startling if they came 
from any other country, as it is a common saying here, that all things new and 
wonderful must come from America, so consequently your reputation is more or 
less at stake in this matter. 

We, throughout Europe, are no doubt a long way behind you in the eco- 
nomical compression of air and the application of the same, due to a variety of 
causes, the chief of which is the air compressing manufacturer ; who, instead of 
trying to construct his compressor on more economical lines and reduce to a 
minimum the loss of power between the steam and the air cylinders, seems to 



r 



PRODUCTION. 79 



have accepted a certain low standard of efficiency, and no serious attempt has 
been made to improve upon it ; it having been taken, that a great loss is inevitable, 
and that compressed air is only used when it is absolutely necessary, such as in 
mining operations, tunnel driving and other dark corners, where other motive 
forces are not practical; but happily this idea is fast dying out, owing largely 
to the publicity compressed air has attained during the last year or so, and the 
fact is being largely accepted that compressed air is not only useful in dark 
confined spaces, but in the open daylight as well, competing alongside of steam 
and electricity, and in many cases where steam is practicable, air is found more 
economical in its application. It speaks volumes for it, that in every case where 
it has been installed, for open quarry work, etc., for operating rock drills, cranes 
and other motors,, the users are strong in its praise, and would not again go back 
to steam. Unfortunately, compressed air in the past has been judged only by the 
loss of power between the steam and air cylinders, and the great convenience 
and saving in application has been overlooked. However, the time is rapidly 
approaching when compressed air will be recognized at its full value, and given 
its proper place. By that time it will be found that there are two kinds of air 
compressors — the good and the bad; the latter, dear at any price. If the public 
in the past had only purchased from well-known and tried manufacturers of this 
class of machinery the result's would have been quite different. 

One reason for our engineers being so long in adopting pneumatic ap- 
pliances has been the difficulty of getting a satisfactory air compressor; and in 
many cases pneumatic tools have been tried and condemned, when it was entirely 
the fault of the compressor in not giving sufficient pressure, and being otherwise 
unsatisfactory. 

There is no class of engine made in this country on so many different 
designs in attempting to accomplish the same purpose as the air compressor, and 
in the majority of cases, the fatal mistake is made of not properly proportioning 
the fly-wheel. It is the apparent simplicity of the air compressor which has 
tempted many old established engineering firms to take up its manufacture as 
a kind of side issue, which needed but little attention ; but many soon discovered 
to their cost, that they had made a mistake, and that to design and manufacture 
a successful air compressor was no simple matter, but one which required years 
of study. As an instance, to show the difference between a good air compressor 
and a bad one, I might give a few details of two I saw a short time ago. One 
was constructed by a well-known and noted air compressor company and the 
other by a well-known fllrm of engineers, who had never before built an air 
compressor. The dimensions of the latter compressor are as follows : Steam 
cylinder 12-in. diam., air cylinder 12-in. x 15-in. stroke. This engine running 
at its maximum speed could not supply air above 20 lbs. pressure per square 
inch, for keeping one 3-in. cylinder by 5^-in. stroke rock drill at work, through 
a large pipe, distant only a few hundred, yards. The other compressor, with 
.dimensions as follows: — 12-in. steam cylinder and 12-in. air cylinder by 14-iii. 
stroke, and running at about two-thirds of its speed, was able to maintain 60 lbs. 
pressure per square inch, with two 3-in. cylinder drills constantly at work, 
through similar size pipe and under the same conditions. Of course, this is an 
extreme case, the first compressor being a badly designed one and the necessity 



So PRODUCTION. 

for reducing clearance spaces in the air cylinder having been ignored by the 
builder. 

I might cite one more instance of some of the bad designs on the market : 
this time a belt compressor, constructed by quite a different firm, but proving 
equally unsatisfactory. The main driving pulleys for operating this compressor 
are about 4 feet in diameter; the fly-wheel pulleys on compressor are about 2 
feet 6 inches in diameter (and very light in construction) ; the air cylinder is 
i6-in. diameter by i8-in. stroke, and running at a speed of about 75 revolutions 
per minute. With this compressor it is found quite impossible to raise more 
than 20 lbs. pressure per square inch ; in fact, this result can only be accomplished 
with difficulty, and abnormal wear and tear on the belts, owing to their lashing. 

In larger size compressors we find much better design, construction and 
workmanship than is found in the small sizes. This is owing to the greater 
demand for big compressors for Colliery work, etc., the makers having gained 
more experience ; but that experience has only led them to proportion their com- 
pressor a little better, and make it more of a mechanical job. (There is, how- 
ever, much yet to be desired in this line). The inlet valves, which are the weak 
point in all our compressors, seem to have undergone but little improvement dur- 
ing the past twenty years. Better material is now being used, and consequently 
the danger of the engine being wrecked by valves 'breaking and falling into the 
cylinder is much lessened. However, even now, it is not found safe to run at 
more than about 300 feet piston speed per minute, as anything faster would ham- 
mer up the yalves, which would then become leaky and dangerous. This is a 
serious drawback, as otherwise the engine would be capable of running double 
the piston speed, which would naturally increase the capacity of the air com- 
pressor. These remarks, of course, apply to compressors with 5 to 6 feet stroke 
and above i8-in. diam. cylinder, which are practically the only type made in this 
country. 

It also not infrequently happens that the compressor manufacturer is not 
sufficiently informed on the subject to know what size air pipes to advise or what 
kind of oil to use in the air cylinder. Consequently, in the first case, too small 
air mains are often put down over long distance, with the natural result of caus- 
ing too much friction, and in the latter case, the air valves become clogged up and 
after a short existence, the air compressor is a complete wreck.. 

Compressed air as applied to steet cars seems to be having but little atten- 
tion and development on this side; and it seems that the conditions are most 
favorable, as there is considerable opposition on the part of the public to having 
the streets disfigured with electric wires. However, all the chief cities have, or 
are about starting the overhead trolley system, but any enterprisuig firm who 
could put some favorable facts and reliable data before some of the corporations 
contemplating the adoption of mechanical power for street car service would no 
doubt have unprejudiced consideration, and a successful installation in any im- 
portant city would be followed by the universal adoption of compressed air.. 
With the exception of London, the compressor power station could be so placed^ 
as to be within 3 to 5 miles of the terminus of the tram lines. 

Take Glasgow (a very large city), and the power stations need not be 
more than 3 miles from the terminus. 



PRODUCTION. 8r 

COMPRESSED AIR.* 

Our earliest authentic records of the application of air in a physical 
or mechanical sense are found in a book by Hero of Alexandria, who lived, so 
we are informed by historians, from 284 to 221 B. C. Hero is said to have been 
a student of Ctasibus, who is credited with producing the first pneumatic air gun. 
Later produced a book of Pneumatics, " Hero's Pneumatics." This was a 
review of the art up to his time, a remarkable work in which is recorded a 
variety of pneumatic devices used mostly by the tricky, yet shrewd, priests to 
intimidate the ignorant, child-like men of those days into an awed and super- 
stitious obedience. Among these pneumatic appliances, the most of which the 
author makes no claims to have invented, is one, the Hero Fountain, a simple 
device quite as familiar to the world as the steam engine. Other early records 
tell of the primitive efforts of Philo of Byzantium and the fathers of the early 
Chaldean Church. But it was only after centuries had rolled by that, so far as 
we know, any advance was made. To Boyle, a physicist, may be credited the 
next mile stone in this field of science, Boyle's law, named after its discoverer, 
and proposed about 1662, sometimes credited to Mariotte, states that at a given 
temperature the volume of a body of gas varies inversely as the pressure, density 
and elastic force, and it is this law, verified time and again since then, which 
forms the foundation of thermodynamics. Dr. Papin is credited with suggesting. 
in 1700, the use of air for forcing carriers through tubes. Eighteen hundred is 
the year in which the blast furnace is claimed to have been introduced into 
Wales. Other physicists have added here and there the laws and theories which 
constitute the science of thermodynamics, and enable us to calculate and predict 
the probable action of our thermal machines. 

Among the many entitled to the most credit the names of Avagardo, Gay 
Lussac, Torricelli and Regnault stand out most prominently. Another period 
equally as important but more recent includes the names of Rankine, Carnot, 
Thurston, De Volson Wood and others who have formulated and collated the 
scattered facts and developed the laws of thermodynamics into an exact science. 
So much has been written by those mentioned and dozens of others about the 
general subject of gases, among which we may include air, that it is hardly pos- 
sible to impart much, that is new except from the practical standpoint; that is, 
from the point of application of the principles to the actual machines. 

To begin with, let us consider air as a material, as it is. In other words, 
it is a substance, and, it so happens, a composite substance. Its constituents, 
speaking now of ordinary air, are oxygen, argon, nitrogen, carbonic acid, and a 
certain amount of water vapor; generally speaking, it is regarded as made up of 
23 parts by weight of oxygen and 'jy parts by weight of nitrogen, or by volume 
21 parts of oxygen and 79 parts of nitrogen. This air surrounds the earth like 
a shell to a depth of about 20 miles. It varies in density from practically nothing 
where it shades off into space to that produced by a pressure of 14.7 lbs., which 
we call "atmospheric pressure." 

At 0° C. (32° F.) and atmospheric pressure (14.7 lbs.) one pound of dry 
air occupies a space of 12.386 cu. ft,, and conversely a cu, ft, of air weighs 0.0807 

* J, J. Swann, iu The Sibley JonrnaL 



82 PRODUCTION. 

lbs. These figures for an average temperature, say 60°, are 13.089 cu. ft. and 
0.0764 pounds per cubic foot. In other words, an increase in temperature with a 
constant pressure increases the volume of this air. Being a substance it has 
properties like other substances. It is elastic and can expand or be compressed. 
This compression may be done in three ways: isothermally, with temperature 
kept constantly by some refrigerating device; adiabatically, in which the tem- 
perature is allowed to increase as it will, the containing vessel being protected 
to keep in the accumulated heat; and a combination of isothermic and adiabatic 
compression, or the system of compression approached in the best machines of 
to-day. 

Before discussing compressed air in the modern meaning of the term, it is 
desirable to divide our subject, and this is easily done because it naturally falls 
into three sub-divisions: 

1. Production. 

2. Transmission. 

3. Use. 

Or the compression, the transmission and the expansion. Air is not a per- 
fect gas, but it is enough so for our purposes ; hence, the laws and formulas used 
in considering a perfect gas may be applied to it as well. 

A perfect gas is one which, when under a constant pressure, will have a 
rate of expansion exactly equal to the rate at which it absorbs heat ; or, a perfect 
gas is one with which, for each given increment of pressure, there will be an 
equal increment of heat. Stated as an equation we have 

(/>) V constant «"^ C^^) p conmn. <^ t 

pv ^ t 

or-^' = ^i^ = (r--=Cconstant) (l) 

in which the prime letters represent a different set of values from p, v and t, 
which are the initial values for pressure, volume and temperature. Reducing 
this to 0° Centigrade and considering one cubic foot of dry air at the sea level, 
we have 

A"^o^ '4 7 X 1 44 X 12 .38 _ 
/„ 460.66 -I- 32 ^^' 

then y = C /'z' = 53-21 X /, 
or in the metric system, 

/ z/ = 29. 20 X /. 

This is simply another way of stating Boyle's, or Mariotte's, law of 
perfect gases, and, while not absolutely true for all gases, it may, for engineering; 
purposes, be employed for the so-called permanent gases, including air. 

As already stated, the relations of pressure, volume and temperature may- 
be considered in two ways, isothermally and adiabatically. 

Consider for a minute Fig. 29, which represents a cylinder with an area of x 
sq. ft. and a length of about 14 ft. filled with air under atmospheric conditions^ 
say 147 lbs. pressure and 60° F. temperature. We will then consider the cylinder 



r 



PRODUCTION. 



«3 



'surrounded by a refrigerating medium or device capable of absorbing any heat 
which may be generated above that which is resident in the surrounding air 
under the atmospheric conditions. If the piston is now advanced, the air is con- 
densed, the molecules have less and less space in which to travel, molecular im- 
pacts increase in frequency and the temperature of the whole gas increases, thus 
giving evidence of the generation of heat. However, if we may use the expres- 
sion, this surplus of heat is absorbed by the refrigerator as fast as produced, and 
we have the relation of pressure and volume called for in the equation p v = C 
(constant), which, graphically, is an equilateral hyperbola asymtotic to the X 
and Y co-ordinate axes. 



d^i 



.iw.«v 



jr 



M 



SiUe<|. 



FIG. 29. 



Adiabatic compression under the same conditions would be accomplished 
by substitution for the refrigerator, lagging or packing which would prevent the 
removal or addition of heat from or to the cylinder. 

The advance of the piston, as in the former cases, decreases the space in 
which the molecules move, hence their movements become more rapid, their 
minute impacts occur with increased frequency and force, and, as a result, there 
is an increase in the amount of heat present in the cylinder. This heat causes a 
positive expansion of the enclosed air, necessitating an application of increased 
power to move the piston. In other words, other things being equal, adiabatic 
compression requires the expenditure of more power than isothermal compres- 
sion. The equation representing this adiabatic compression must then be dif- 
ferent from isothermal compression, and it can be shown mathematically that 



p v^ - p, v,"^ = Constant. Thus : D//= O. 
C^<i/;=—pdv 



where Cv=specific heat at constant volume 
C ^specific heat at constant pressure 

dividing ^=-&^=_,-^ 
Integrating, log^ = ^°s(^) 






84 



PRODUCTION. 



When pi and vi are the initial limits, the other limits being general. 
"hence, p v = p^ ^."^ =■ constant 



eliminating^ by using ;Jz;= Constant X / 



7^ 



These are the equations of adiabatics for a perfect gas in which v, p, t, are initial 
limits, and Vi, pi, t: other values taken anywhere, or terminal. The term } is a 
constant and is the ratio of the specific heats, which are constant for perfect gases. 
That is. 



C 



for 



c - ' 
0^375 

o, 1689 

It is thus seen that the apparatus which, in compressing from one condi- 
tion to another, effects the greatest cooling \\\\\ be the most efficient. 



1.406. 



COMPRESSION. 



To all intents and purposes the compression which we obtain even in the 
best forms of air compressors is nearh^ adiabatic, and even if it is not, the con- 



Y 



tA 



tA 



A/. 



1\ 

1 
1 

1 


1 ^ 


N 




1 

1 


/»! 




^^> 


*■ ^ F- 


- f-^ 




T 1 


1 

* Xm X 

1 


> 


<L^ 


• V A 



N 



X 



FIG. 29a. 



sidering of it as such is an error on the right side. Such being the case, let us 
consider the work necessary to compress a cylinder full of air. To start with. 
we have our cylinder either single or double acting, connected with a receiver or 
reservoir, the passage to which is closed by a discharge valve. The pressure in 
this reservoir is something above atmospheric, say Fm : our cylinder is filled with 
free air under atmospheric conditions. As the piston is advanced towards the 
closed end the pressure of the enclosed air increases along the curve M N to M, 
which is the pressure Pm of the receiver. The discharge valve then lifts and 



r 

M PRODUCTION. 85 

the further advance of the piston performs the work of forcing the now com- 
pressed air into the receiver against approximately a constant pressure. 

We thus have the work done in a complete stroke divided into two por- 
tions. That of compression and that of delivery. The piston is, of course, 
shoved ahead by the piston rod, in turn connected with some form of engine. 
There is, however, an additional pressure ?f 15 lbs. per sq. inch assisting, due to 
the free air entering the inlet valve on the other end of the cylinder. This pres- 
sure is balanced, however, by a like pressure at the exit of the receiver. 

If, Fig. 29a, we let the increasing pressure of the air be p, which at ^ would 
be 14.7 lbs., atmospheric pressure, and pm the receiver pressure, F ihe piston area, 
and*x the distance from the piston is at any moment. Then the work done 
in compression will be represented by the area M N L and that of delivery by the 

area M^M L NK 

f area ^ 
M M L I /»D 

work of =«'. = "J ^P^p-P.)dx ...(a) 

comp. J 
in which p and x are variable 
r area M^ ] 
M L Ni I /.o 

1 work of ( = «'^ = -J ^P^P^ ^P.)dA (b) 

[ delivery J 
in which /> = /'m and is constant 
adding (a) and {h) and simplifying, we have, work per stroke 

= ff-=7e,, + 7£/, = 3-.nA]l-^^)^[^ (2) 

For convenience in approximate calculations, the following table will prove 
of value : 

TABLE 8. — HORSE POWER DEVELOPED TO COMPRESS 100 CUBIC FEET OF FREE AIR, FROM 
ATMOSPHERE TO VARIOUS PRESSURES. 



Gauge 


One-Stage 


Gauge 


Two-Stage 


Pour-Stage 


Pressure 


Compression 


Pressure 


Compression 


Compression 


Pounds. 


D. H. P. 


Pounds. 


D. H. P. 


D. H. P. 


10 


3.60 


60 


11.70 


10.80 


15 


5.03 


80 


13.70 


12.50 


20 


6.28 


100 


15.40 


14.20 


25 


7.42 


200 


21.20 


18.75 


80 


8.47 


300 


24.50 


21.80 


35 


9.42 


400 


27.70 


24.00 


40 


10.30 


500 


29.75 


25.90 


45 


11.14 


600 


31.70 


27.50 


50 


11.90 


700 


33.50 


28.90 


55 


12.07 


800 


34.90 


30.00 


60 


13.41 


900 


36.30 


31.00 


70 


14.72 


1000 


37.80 


31.80 


80 


15.94 


1200 


39.70 


33.30 


90 


17.06 


1600 


43.00 


35.65 


100 


18.15 


2000 
2500 
3000 


45.50 


37.80 
39.06 
40.15 



+ Church's Mechanics of Engineering, page 637. 



86 PRODUCTION. 

Two-, three-, and poly-stage compression employs exactly the same for- 
mulas, introducing, however, the condition of inter-cooling. At the end of the 
compression in the first cylinder the discharge valve opens and the air passes out 
into the inter-cooler, which is being emptied at the same instant by the air passing 
into the high pressure cylinder. The cubic dimensions of the cylinder should 
be such that the compressed charge can pass in and just fill the cylinder, thus pre- 
venting any loss of pressure due to expansion. 

The work involved in compressing a given weight of air, say one pound, 
is obtained by assuming pressures and temperature, or by measuring them in the 
case of an operating engine, and employing the formulas already given. Assume 
pi as our original pressure with an absolute temperature Ti. Let /^c = pressure 
at end of the first compression. We have the equation already given (in which 
n = >). 



;^,-'^''[(.fS^'-'] 



R is a constant = C. The second stage starts at /c and runs to pi with a final 
temperature T2 



"-,-;^-n[(|)^'-.] 



Adding, we have, 



n - I 

To determine the value oi pc which will make the work a minimum, we 
make the first differential equal zero, which gives, 

and using this value in the above combined equations, we get the expression 



^=ii^^^[(f'^-)] 



The same process can be employed for three, four or others stages. 
Stated differently this formula means that 

Total work=<^°°^"*^ggg>^ 



n — I 



IV J. i 

/absolute initial \ ^ 

\ temperature / 



(constant) 

r/ final pressure x ^^^J-;;^^^^^ -1I 
LVinitial pressure/ J 



r 



PRODUCTION. 87 



It is sometimes desirable to know the mean effective pressure resulting 
from a given compression. This may be obtained from the formulas 



III 



Adiabatic = ^^ ;>,[(^ A^-^ _ ,1 

Isothermal '= ^, log, -^ 
A 



These are derived by dividing the equations representing the total work of 
adiabatic compression and delivery of one pound of air by Vi 



and 



^*A.t;^log. (A) 



In determining the efficiency of compression it is usual to divide the total 
isothermal work by the total work of adiabatic compression, the initial pressures 
and temperatures and the final pressures being the same in both cases. This 
applies to both cases. 

For more than one stage the numerator remains the same, the denominator 
alone changing to correspond with the proper number of stages. 

The temperature (absolute) at the end of the compression is found from 
the formula 

The air at the temperature, T^, passes to the reservoir or into the trans- 
mission mains, where it loses heat by conduction and radiation until it reaches 
a final temperature, T^. During this cooling the volume has decreased, but the 
pressure has been maintained by air constantly being forced into main by the 
compressor, which keeps the density, y, constant. The mechanical equivalent of 
the heat lost in this cooling is lost work and naturally reduces the efficiency of 
the machine. 

To-day the range through which compressed air is used calls for pres- 
sures from as low as 10 pounds, as in the case of pneumatic tubular dispatch, 
to as high as 3,000 pounds, which is the maximum pressure used for street rail- 
way work. However, by far the greatest field is found between 50 to 1,000 
pounds. 

For convenience we may sub-divide the production of compressed air into 
three pressures. 

1 Low from 5 to 50 poundK. 

2 Medium from 50 to 6(>0 pounds. 

3 High from 500 to 5000 pounds. 

The first of these finds its most extensive use in blast furnace operation, 
for which purpose the engines are nearly all of the vertical slow speed Corliss 
type, with large air cylinders. 

This first class is almost universally of the single compression type; that 
is, all the compression is done in one cylinder. The second or medium class in- 



88 



PRODUCTION. 



eludes by all odds the greater portion of air machinery used at the present time. 
In it are all the compressors operating coal cutters, rock drills and machine tools 
of every sort, such as hammers, chippers, riveters, etc. In this class single and 
double or compound compression is customary. 

With pressures above about lOO pounds compounding is necessary, both 
as a matter of economy and for safety. The term compounding is here men- 
tioned for the first time and calls for an explanation. 

When we compress air only as high as lOO pounds in a single cylinder with- 
out cooling, that is, adiabatically, temperatures ranging from 475° to 550° F. 
are reached. In other words, the cylinder walls and working parts are hot 

TABLE 9. — HEAT PRODUCED BY THE COMPRESSION OF AIR. 





Pounds 


Pounds 




Temperature 


Total 


Atmos- 
pheres. 


per sq. in. 

above 
a vacuum. 


per sq. in. 

above 

atmosphere 

gage pressure. 


Volume in 
cu. ft. 


of air 

throughout 

the process, 

degrees F. 


increase of 

temperature 

degrees F. 




Pressure. 


Pressure. 








1.00 


14.7 


0.00 


1,000 


60.0 


00.0 


1.10 


16.17 


1.47 


.9346 


74.6 


14.6 


1.25 


18.37 


3.67 


.8536 


94.8 


34.8 


1.50 


22.05 


7.35 


.7501 


124.9 


64.9 


1.75 


25.81 


11.11 


.6724 


151.6 


91.6 


2.00 


29.40 


14.70 


.6117 


175.6 


115.8 


2.50 


36.70 


22.00 


.5221 


218.3 


158.3 


3.00 


44.10 


29.40 


.4588 


V 255.1 


195.1 


3.50 


51.40 


36.70 


.4113 


287.8 


227.8 


4.00 


58.80 


44.10 


.3741 


317.4 


257.4 


5.00 


73.50 


58.80 


.3194 


369.4 


309.4 


6.00 


88.20 


73.50 


.2806 


414.5 


354.5 


7.00 


102.90 


88.20 


.2516 


454.5 


394.5 


8.00 


117.60 


102.90 


.2288 


490.6 


430.6 


9.00 


132.30 


117.60 


.2105 


523.7 


463.4 


10.00 


147.00 


132.30 


.1953 


5.54.0 


494.0 


15.00 


220.50 


205.80 


.1465 


681.0 


621.0 


20.00 


294.00 


279.30 


.1195 


781.0 


721.0 


25.00 


367.50 


352.80 


.1020 


864.0 


804.0 



enough to melt ordinary solder, or as hot as steam between 950 pounds and 1,000 
pounds pressure. With this temperature the greatest difficulty is experienced 
in lubricating the cylinders and valves, owing to the valves and passages becom- 
ing clogged with a thick gummy substance, or a coke-like material. This is really 
burnt oil, easily explained when we remember that the flash point of the most 
staple cylinder oils is not over 450° F., and is on an average nearer 425°. In ad- 
dition to the inconvenience and loss of efficiency due to clogged discharge ports 
and pipes, and the heat and annoyance and increased wear due to the hot parts, 
there is a real and considerable danger from explosions, which result from the 
formation of an explosive mixture of vaporized oil and compressed air. In the 



[ 




PRODUCTION. 



89 



early days of compressed air several unfortunate accidents resulted from dis- 
regard of this heat of compression. 

In a compound compressor, that is, one in which the air is partially com- 
pressed in one cylinder, then transferred to a second cylinder and the compress- 
ion continued to the maximum, the opportunity for cooling the air and pre- 
venting this increase of temperature is doubled because the cylinder surface is 
twice as great as in the first case, and also an opportunity is afforded to pass the 
air through what is called an inter-cooler, which is a form of reservoir designed 
to bring the air which passes through it into intimate contact with cooling sur- 
faces, which are continually cooled by running water. 

Assuming, again, a compression of 100 pounds. If we draw air into the 
first cylinder at atmospheric pressure and temperature and compress it to about 



1000° 

900° 
800° 
"700° 


Pressure by Atmospheres 

i.l»OWH»>0»0» ^ QD.D oC 5S 


s:s;st^ss^l2_ 


\ 










































\ 
































.^ 




-^ 




0.8 


\ 




























■'^ 




. 




^^ 


""^ 


0.7 
0.G 


21 
3 000 

2«ioo° 


\ 














fro*" 


100^. 


^^ 


















F- 





\ 










x.^ 


C^ 




.j:^ 


«o . 










^- 











0.5| 




\ 


^' 






^ 




H6»* 


s^ 


jrom. 


i^ 




















ft nw 

M0° 

100" 
W° 

0° 

; 












_^ 


^ 
































/. 


^ 


xd 




^ 


^iStic^ 


Curu 


> 
























0.2 


// 




y" 




<Sff>e 


::22^ 


£-2fl 




" 

























y 
























— 








































•^ N 


! ; 


: \ 


S 5 
10 c 


^ ! 


« 


1 \ 

< 


I \ 


1 


5 


! i 




1 


2 

* 


I \ 


1 i 


1 1 

» < 


! \ 


I 




1 

3 



FIG. 30.^^SAUNDERS' CURVES.* 



30 pounds, the resulting temperature is from 200° to 260°, according to the effect- 
iveness of the cooling jackets of the cylinder. If the air then is passed through 
an intercooler of sufficient capacity, the temperature is reduced to practically that 
of the intake, and possibly something lower, say 70 degrees ; it then passes on to 
the second cylinder, quite cool, and at a pressure of 30 pounds. In this cylinder 
it is raised to 100 pounds, and here again the temperature increase will be only 
from 200° to 250°, which is too low to cause any inconvenience. 

. Compounding, however, does not result in any material economy, unless 
the air is thoroughly cooled between the stages. Hot air in the cylinder of an air 
compressor means a reduction in the efficiency of the machine, because there is 
not sufficient time during the stroke to cool thoroughly by any available mean.s. 



• W. L. Saunders. " Compreeeed Air Production. 



90 



PRODUCTION. 



Water jacketing, the generally accepted practice, does not by any means effect 
thorough cooling. The air in the cylinder is so large in volume that but a frac- 
tion of it is brought in contact with the jacketed parts. Air is a bad 
conductor of heat and takes time to change its temperature. The piston, while 
pushing the air toward the head, rapidly drives it away from the jacketed sur- 
faces, so that little or no cooling takes place. This is especially true of large 
cylinders, where the economy effected by water jackets is considerably less than 
in small cylinders. Leaks through the valves or past the piston will explain 
many isothermal cards, and until something better than a water jacket is devised 
it is well to seek economy in air compression through compounding. 

In the case of high pressures such as those indicated in the third class, 
that is, from 500 to 5,000 pounds, it is essential to employ three or four stages; 
the same general process is emploj'^ed as in the compounding, there being first, 
second and third compressions, and first, second and third intermediate inter- 
coolers. This arrangement makes it possible to deliver air under these high 
pressures at a temperature even less than that of the atmosphere. Of course, 
there is quite a range between summer and winter conditions, and these have 
their effect ; but the advantages of stage compression are facts. It has been 
found that a difference of 5** at the inlet valve causes a variation of about i per 
cent, in the efficiency, and the curves shown afford an idea of the increased work 
brought about by a slight increase in initial temperature. 



TABLE 10. — INCREASED EFFICIENCY RESULTING FROM STAGE COMPRESSION. 
"compressed AIR." 



i 


One Stage. 


Two Stage. 


Four Stage, 


p 


% of work 


% of work 


% of work 


% of work 


% of work 


% of work 


s^ 


lost in 


lost in 


lost in 


lost in 


lost in 


lost in 


^ 


terms of 


terms of 


terms of 


terms of 


terms of 


terms of 


1 


leotherm&l 


Adiabatic 


Isothermal 


Adiabatic 


Isothermal 


Adiabatic 


Compression. 


Compression. 


Compression. 


Compression. 


Compression. 


Compression. 


60 


30. % 


23. % 


13.38^ 


11.8 % 


4.65,^ 


4.45^ 


80 


34. 


25.26 


15.12 


13.12 


5.04 


4.80 


100 


38. 


27.58 


17.10 


14.62 


8.00 


7.41 


200 


52.35 


34.40 


23.20 


18.88 


9.01 


8.27 


400 


68.60 


40.75 


29.70 


22.90 


12.40 


11.04 


600 


83.75 


44.60 


32.65 


24.60 


15.06 


13.10 


800 


90. 


47.40 


35.80 


26.33 


16.74 


14.32 


1000 


96.80 


49.20 


39.00 


28.10 


16.90 


14.45 


1200 


106.15 


51.60 


40.00 


28.60 


17.45 


14.85 


1400 


108. 


52. 


41.60 


29.4 


17.70 


15.00 


1600 


110. 


53.3 


42.90 


30.0 


18.40 


15.54 


1800 


116.80 


54. 


44.40 


80.6 


19.12 


16.05 


2000 


121.70 


54.8 


44.60 


30.8 


20.09 


6.65 

















PRODUCTION. 91 

The four stage compressors are used for charging mine locomotives, for 
power transmission and for such special apparatus as charging of pneumatic 
street cars, etc. 

The preceding table will serve to illustrate the large saving that it is pos- 
sible to effect by compounding. From it the percentage of work lost by the heat 
of compression, taking isothermal compression, or compression without heat, as 
a base, can be obtained for pressures from 60 to 2,000 pounds. 

In the above figures no account is taken of jacket cooling, as it is well 
known among pneumatic engineers that water jackets, especially cylinder jackets, 
though useful, and perhaps indispensable, are, as just explained, inefficient, 
especially so in large compressors. The two and four stage figures in this table 
(columns 3 and 4) are based on reduction to atmospheric temperature, 60° Fah- 
renheit, between stages. This is an important condition, and in order to effect 
it much depends on the inter-cooler, and a rule which might be observed to ad- 
vantage among engineers is to specify that the manufacturers should supply a 
compressor with coolers provided with one square foot of tube cooling surface 
for every 10 cu. ft. of free air furnished by the compressor when running at its 
normal speed. 

The table shows that when air is compressed to 100 lbs. pressure per sq. 
in. in a single stage compressor, without cooling, the heat loss may be 38 per 
cent. This condition, of course, does not exist in practice, except, perhaps, at 
exceedingly high speeds, as there will be some absorption of heat by the exposed 
parts of the machine. It is safe, however, to say that in large compressors that 
compress in a single stage up to 100 lbs. gauge pressure, the heat loss is 30 per 
cent. This, as shown in the table, may be cut down more than one-half by com- 
pounding or compressing in two-stages, and with three-stages this loss is brought 
down to 8 per cent., theoretically, and perhaps to 3 per cent, or 5 per cent, in 
practice. 

A great deal of time and attention have been devoted to coolers and inter- 
coolers by the larger manufacturers of air compressors, and the most successful 
form now employed resembles a surface steam condenser. In this, speaking now 
of the "Sergeant" type (Fig. 31), the heated air, direct from compressors, passes 
into an upper opening, and down between a large number of small tinned copper 
tubes, held vertically in a sort of chimney. The air finally emerges into the shell 
portion of the inter-cooler and is free to travel through the top to the outlet tube. 
The smaller tubes mentioned terminate at either end in plates, into which thev 
are expanded. The cooling water enters through the lower pipe and is forced 
upwards through the cooler tubes, and finally emerges at the water outlet at the 
top. The water tubes are set so close together that they divide the incoming 
stream of air into thin sheets and bring it into very intimate contact with the 
cooling surface. As stated, the air is caused to enter at the top and pass down- 
ward, while the cooling water enters at the bottom and passes upward. This 
is the accumulating principle upon which all successful liquid air apparatus have 
been constructed. 

A properly designed inter-cooler should reduce the temperature of the 
compressed air to its original point ; that is, to the temperature of the intake air. 
In can do even more than this, especially in winter, when the water used in the 



92 



PRODUCTION. 



inter-cooler is of low temperature. A simple coil of pipe submerged in water 
is not an effective inter-cooler, because the air passes through the coil too 
rapidly to be cooled in the core, and such inter-coolers do not sufficiently split 
up the air to enable it to be cooled rapidly. This splitting up of air is an impor- 
tant point. A nest of tubes carrying water and arranged as described, so that the 
air is forced between and around the tubes, is an important point in an efficient 
form of inter-cooler. If the tubes are close enough together and are kept cold, 
the air must split up into thin sheets while passing through. Such devices are 




FIG. 31. — THE SERGEANT INTERCOOLER. 



naturally expensive ; but first cost is a small item when compared with the effi- 
ciency of the compressor, measured in the coal and water consumed. 

Receiver-intercoolers are more efficient than those of the common type, 
because the air is given more time to pass through the cooling stages, and 
because of the freedom from wire drawing which may take place in intercoolers 
of small volumetric capacity. 

Aftercoolers are in some installations as important as intercoolers. An 
aftercooler serves to reduce the temperature of the air after the final compress- 
ion. In doing this it serves as a dryer, reducing the temperature of air to the 
dew point, thus abstracting moisture before the air is started on its journey. In 



PRODUCTION. 93 

?old weather, with air pipes laid over the ground, an aftercooler may prevent 
accumulation of frost in the interior walls of the pipes, for where the hot com- 
pressed air is allowed to cool gradually, the walls of the pipe in cold weather act 
like a surface condenser, and moisture may be deposited on the inside for the same 
reason that we have frost on the inner side of a window pane. In using these 
aftercoolers, and also intercoolers, it is good practice to allow from 8 to lo cu. 
ft. of free air per minute for each square foot of cooling surface. Further, an 
allowance of i lb. of water for each 2 cu. ft. of free air should be made. 

Makeshift aftercoolers are frequently employed, such as abandoned boilers, 
sections of large pipe, which are placed outdoors and provided with a drain and 
relief valve. These serve in special cases, but for ordinary practice it pays to use 
a standard aftercooler. The use of an aftercooler cannot be too strongly recom- 
mended, as it will be the means of avoiding many of the ills usually laid at the 
door of the compressing apparatus. 

The heat given out or wasted in this cooling down to receiver temperature 
may be represented by the equation 



or, by substitution. 



0=C,a.-T.,) 

which, when translated into ordinary language, means that the quantity of heat, 
(Q) equals the specific heat at a constant pressure, times the absolute initial 
temperature, multiplied by an expression made up of the quotient of final pres- 
sure divided by the initial pressure raised to the power, from which i is 

n 
subtracted, n being an exponential occurring in the equation of compression 
p v^^ = C (constant), and will depend upon the degree of perfectness of cooling 
during compression, ranging from i for isothermal compression to 1.414 in 
the case of adiabatic. 

In selecting an air compressor, the conditions under which it is to operate 
must be carefully considered, as it is impossible to design a single compressor 
which will fit all conditions. The most important factors are: pressure desired, 
the character of apparatus to be operated, the cost of fuel, allowable space and 

- quantity of air required. Generally speaking, economy has not been the most 
important consideration until recently. Where a large volume of air is required, 
and the character of the work is fairly constant, so that the demands upon the 
compressor are not varying to too great an extent, and where the cost of fuel 

y makes it desirable lo produce the air at a small cost, it has been found by experi- 
ence that at a fairly low speed, compound Corliss engine gives the best results. 

]-] In such plants as may be termed permanent, a compressor using a compound 

Corliss engine, running condensing, with compound air cylinders (the air being 

mtercooled and also aftercooled), will be found to transfer the mechanical power 

' available air power most economically. For coal mining and places where 



94 PRODUCTION. 

the service is intermittent, fuel is cheap and the service of a skilled engineer is 
not desirable, it has been found that a "straight-line" single acting compressor 
best meets the conditions. 

In compressed air practice, as in engine or boiler practice, it is well to 
install a larger machine than is needed at the time, because it invariably happens 
that the demand increases, and compressors, in common with other apparatus, 
work best under designed conditions. 

All forms of compressor engines in which energy is used to compress air, 
can be sub-divided into rotary compressors, such as blowers and fans used for 
large volume low pressure work, and reciprocating compressors following in 
form the conventional steam engine design. That is, a horizontal or vertical 
cylinder, piston, cross head, connecting rod, crank and fly wheel. These may 
again be sub-divided into those driven by steam, or driven by water power, belts 
of one sort or another, or motor driven, either direct or geared. It is this 
general class of air, or, for that matter gas, compressors which has slowly but 
surely made for itself a name, and has developed into one of the large American 
industries. 

The three classes into which reciprocating apparatus for the production 
of compressed air naturally fall, and considerations of convenience, first cost and 
economy of operation, have resulted in the development of certain distinct types 
of compressors, which may be classed under the general heading of self-con- 
tained, steam actuated compressors, and those operated by some external means. 

Both classes may be simple, duplex or poly-compression machines. Ex- 
perience, however, has sifted out the best forms, which are as follows : 

STEAM ACTUATED. 

(i). Straight Line; that is, steam and air cylinders in one line, mounted 
on a continuous girder frame. A self-contained, reliable type; a great user of 
steam, but a most satisfactory type where fuel is inexpensive and where a large 
amount of air is not needed. Usually single stage compressors, but often built 
in two or three stages. 

(2). Duplex. Usually built with two parallel engines, connected by 90 "^ 
cranks to a single flywheel shaft, with air cylinders behind each steam cylinder. 
Both steam and air cylinders are the same diameter. This type makes no great 
pretense at economy, but finds an extensive field in locations where fuel is not 
high and where simplicity and small first cost are important, and where con- 
siderable air or high pressures are desired. 

(3). Compound. Of the same general character as the duplex, except that 
either or both air and steam cylinders are compounded. In some cases the engine 
may be run condensing. This is, however, hardly necessary, except for very 
large sizes, where it is far more desirable to use the last class, or Corliss type. 

(4). Corliss Type. As implied in the name, this class includes compres- 
sors in which the engine portion employs the well-known Corliss valve motion. 
Such compressors, with few exceptions, are of the horizontal type, the air 
cylinder or cylinders, as the case may be, being placed tandem to the steam 
cylinders. They are employed where the volume of air desired and the fuel con- 
ditions demand the most economical form of engine. They are usually com- 
pounded, both for steam and air, and usually run condensing. 



PRODUCTION. 



95 



PORTABLE AIR COMPRESSING OUTFIT. 

The long felt want for a compact and serviceable Mounted Air Compressor 
has been lately supplied in a neat design, by Fairbanks, Morse & Company, of 
Chicago, as shown in the cut herewith. 

The machine consists of one of their Combined Gasoline Air Compressors, 
mounted complete on a truck, making a portable outfit which can be easily drawn 
about. It is supplied with two square water tanks; one for cooling the engine 
cylinder and the other for cooling the air cylinder. The air receiver tank is 
located under truck and connected to compressor with unloading valve interposed, 
thus maintaining a steady and uniform pressure. The gasoline tank is suspended 
at back of truck and under cylinder. The engine is fitted with a silencer for ex- 




FIG. 32. — PORTABLE AIR COMPRESSOR. 



haust, is equipped with both electric and torch ignitors, and is all connected up 
ready to run. 

The compressor illustrated herewith was built for the Cleveland Ship 
Building Company, to be used in connection with pneumatic riveting tools in the 
construction and repairing of vessels. 

It will be noticed that the machine is self-contained on one iron frame, and 
the pistons of the power cylinder and the air cylinder are connected by distance 
rods. In this way one crank and connecting rod serves for the operating of both 
power and air pistons. 

The machine has a capacity of 70 cubic feet at 80 pounds pressure. Gaso- 
line is used for fuel and as the engine is of about 12 horse power, the machine if 



96 PRODUCTION. 

kept to its full load would consume approximately twelve gallons of gasoline for a 
run of ten hours. 

The engine is equipped with an automatic governor which feeds fuel in pro- 
portion to the amount of work supplied, which in this case would be the quantity 
of air delivered. 

The air end is fitted with an automatic unloading valve. This valve con- 
trols the pressure, keeping it to a given point. When the amount of air used is 
less than that delivered, the unloading valve comes into action, and the air cylinder 
is cut out, thus relieving the load upon the engine, and by this fuel is saved. 



COMPRESSED AIR VS. ELECTRICITY. 



BY FREDK. S. WATJCINS, M. E. 



Closely allied to the generation of power, the transmission of power is a 
problem continually increasing in importance. Whatever the method used to 
convert the natural forces into useful work, the next problem is what system to 
employ to transmit this power to a distance, to be used as the circumstances of 
any particular case may require. 

Although many different contrivances are in use for transmitting power 
within comparatively short distances, when we consider distances of say i,ooo 
feet or over, but two methods have yet attained any special prominence — elec- 
tricity and compressed air. The rapidly awakening interest in the latter is but 
an indication of the future before it, when its general adaptability becomes better 
known. 

In any problem of this class, in order to properly select from several dif- 
ferent systems, we have the following points to consider: 

1. First cost of complete plant. 

2. Efficiency of system. 

3. Cost of operation, including repairs. 

4. Reliability, or freedom from break-downs. 

5. Difficulties met with in operation. 

With the first cost we must also consider the efficiency or percentage of 
useful work realized, for as we are figuring upon a certain amount of power to 
be delivered at the end of the line, it is necessary to have a plant of sufficient { 
size to deliver this amount of power, after allowing for all losses. 

Any method requiring a number of separate stages, each with its own 
apparatus more or less complicated, must necessarily have large losses, requiring jj 



PRODUCTION. 97 



riB^5cpenditure of more work to obtain the final result, and this is one important 

■' point in which compressed air has an advantage. 

Starting the same as an electric plant, with the prime mover, generally a 
steam engine, we find at once in the usual type of direct connected air compressor 
a machine so comparatively simple in construction, that good practice will show 
an efficiency in the compressor of 90 per cent, of the energy of the steam. The 
compressed air has then only to be conducted through a properly constructed 
pipe line to the point of application, in which practical tests have shown the loss 
to be less than 10 per cent, in distances of one mile. 

In transmitting electricity to any distance the losses are heavy, requiring 
constant attention to the proper insulation and protection of the line, a slight 
accident to which would cause an enormous loss. Where compressed air can 
safely be relied upon for a loss of less than 10 per cent., electricity would ordi- 
narily suffer a loss of not less than 30 per cent., frequently a much higher one. 
This shows that considerably less boiler and engine capacity is required by the 
compressed air plant, reducing first cost by no small amount. For transmitting 
the power, the pipe line required by an air plant may usually be taken at about 
the same as the cost of an electric line for the same power. Strange as it may 
at first seem to compare a pipe line to a copper wire in cost, when it is taken into 
account that the pipe requires no provisions beyond being tight, requiring no 
special protection against the elements, where the wire must be carefully insulated 
and strung on poles or placed in expensive underground conduits, all involving 
expensive outlays for labor and material, we at once see the cost more or less 
equalized. 

Arrived at the point of application at the end of the line, the same sim- 
plicity always attends the compressed air operations, for we need but a properly 
designed engine built to perform its special duty, and ordinarily giving out in 
useful work 90 per cent, of the power received from the compressed air. We 
have in this instance about 72 per cent, of the power of our prime mover trans- 
formed again into useful work one mile away. Even if the electric motor had 
the same 90 per cent, efficiency, it would give out at the end of the line but 57 
per cent, of the power of the prime mover, at least 10 per cent, having been lost 
in the generator, and 30 per cent, of this afterwards lost in the line. We have 
then 57 per cent, realized, as compared to 72 per cent, realized by the compressed 
air system, or in other words, the latter system would require that proportion less 
in boiler and engine capacity. This explains, in connection with the relatively 
lower cost of the machinery, why it is that a compressed air plant is so much 
lower in first cost than an electric plant delivering the same amount of power. 

As for the cost of operation, since the compressed air plant requires less 
power to start with, it requires less fuel to supply the necessary power; the 
amount invested being less, it represents less interest on the capital, and a smaller 
amount to be annually marked off for depreciation; the construction throughout 
being more simple and less liable to accidents, the item of repairs is very ma- 
terially reduced, 



98 PRODUCTION. 

Regarding the reliability, when we consider that compressed air is but little 
affected by atmospheric changes, and that all mechanism is readily accessible for 
repairs, we see that there is but little to get out of order, and only to be quickly 
and easily repaired. One greatly overrated cause of trouble has been the "freez- 
ing" or more properly "frosting" of the moisture contained in the air upon the 
expansion of the compressed air in the cylinder of the machine. This has been 
overcome in modern appliances, and when we hear of a compressed air machine 
freezing, we know it to be a case of carelessness or poor design, things that no 
process can always be free from. 

The difficulties encountered in electrical operations are numerous, and in 
many cases impossible to overcome. Everything must be guarded with the clos- 
est scrutiny, demanding the highest skilled and educated labor ; lightning, mois- 
ture, etc., are constant causes of trouble; extreme care is required by the opera- 
tors to avoid receiving the dangerous and often fatal current ; the machinery runs 
at high speed, requiring buildings and foundations of the most substantial con- 
struction. 

Compressed air has none of these difficulties to contend with. The com- 
pressor is but little more than a steam engine with one or more extra cylinders 
and their valves, all of simple design; it runs at safe speeds, is clean, compara- 
tively noiseless, and safe in every way, and the same may be said of the com- 
pressed air machine at the other end of the line, considered in itself. 

In addition to other advantages, the expanding air exhausted into the at- 
mosphere is a medium under control for ventilating and cooling, a feature often 
of importance in engine rooms, and particularly so in mining. 

Advance in any line 'always has a certain amount of prejudice to overcome, 
and compressed air has this to encounter in its progress. Its advocates in no 
way attempt to underrate the importance electricity holds in fields peculiarly 
adapted to itself, in these it still reigns supreme. Give compressed air a stand 
on its own merits, with appliances to suit the conditions, and we have a medium 
of transmission convenient and economical, and susceptible of a wonderful 
variety of applications. — Industrial Reporter. 



THE VOLUMETRIC EFFICIENCY OF AIR COMPRESSORS AT HIGH 

ALTITUDES. 

It is well known that an air compressor will not deliver the same amount 
of compressed air at any given high altitude that it does at sea level. The per- 
centage of delivery, or the volumetric efficiency of the compressor, is sometimes 
assumed to be the same for air compressed to any pressure. This is not, however, 
the case, and the supposition that it is may in some cases lead to serious conse- 
quences, especially if the compression of the air is considerable. Thus, the per- 



r 



PRODUCTION. 99 



centage of compressed air delivered at an elevation of 10,000 feet, at a gauge pres- 
sure of 30 lbs., is only 76 per cent, of what it would be at sea level ; whilst if the 
air is compressed to 80 lbs. gauge pressure, the efficiency is only 715^ per cent. 
Therefore, assuming that an air compressor will deliver at sea level 100 cubic 
feet of air compressed to 30 lbs. gauge pressure, it will, with the same piston 
speed and number of strokes, deliver only 'jd cubic feet of air, compressed to 30 
lbs., at an elevation of 10,000 feet above the sea. The equivalent volume of free 
air is, however, the same in both cases. 

Hence, we see that the efficiency diminishes as the pressure to which the 
air is compressed increases, these differences of efficiency being, however, greater 
in proportion for the lower pressures than for the higher ones. The formula for 
calculating this efficiency is a very simple one, namely: 

A 04-14-72 

Efficiency = 



G+A 14.72 

where 

A=Atmospheric pressure at any elevation, 
G=Gauge pressure, 

G+A=Absolute pressure at any elevation, 
G+i4.72=Absolute pressure at sea level. 

The atmospheric pressure at any elevation is easily found by means of the 
following original but simple formula, which, it need not be said, is an empiric 
one: 

57,000 N — N^ 

Atmospheric pressure at any elevation = A =14.72 

100,000,000 
where 

N=Elevation in feet at which the'pressure A is sought. 

This formula gives results in some cases varying about one-sixth of one 
per cent, from certain published tables, but it has the advantage that when plotted 
it gives a perfect curve, which no table that I have seen will do. 

To find the volume of air compressed to any pressure, which is equivalent 
to a given volume of free air, at any elevation, we have the formula — 

Volume compressed air = Volume free air f ) 

A being, as before, the atmospheric pressure at the given elevation. 

WILLIAM cox. 



USEFUL COMPRESSED AIR FORMULAS. 

In the application of compressed air errors sometimes occur because there 
are no available rules and formulas which apply to the subject. I have, there- 
fore, prepared the following simple formulas, which I have used in my experience: 



loo ■ PRODUCTION. ~ 

Rule to Describe the Isothermal Curve or to find the Pressure at Any Point 
IN THE Stroke of an Air Compressor During Isothermal Compression 
OR Constant Temperature. 

Mariotte's law : The pressure of any gas varies in the inverse ratio of the 
volume, the temperature remaining constant, or 

P 
(a) P'==- 

y 

P' being the absolute pressure at any point of the stroke ; 

P the original absolute pressure; 

V the volume corresponding to the required point of the stroke. 

Required the pressure at one-half the stroke, compressing isothcrmally. 

IS 
P' = — ^^30 lbs. absolute — 15 ^^ 15 lbs. gauge pressure. 

V2 
Required the pressure at seven-eights of the stroke. 

15 
P' = — =: 120 lbs. absolute — 15 = 105 lbs. gauge pressure. 

Required the pressure at one-quarter of the stroke. 

15 
p' = — = 20 lbs. absolute — 15 = 5 lbs. pressure 

Va 

Mariotte's law also applies in determining change of pressure in volumes 
of compressed air due to change of volume. 

Given a volume of air, say i cu. ft., at a pressure of 30 lbs. on the gauge, 
what will be the pressure indicated if this air is forced into one-half the space? 

I X (30 + 15) 

(&) P' = ^ = 90 lbs. absolute — 15 ^^ 75 lbs. gauge pressure. 

V2 

Reversing the problem : Given a volume of air, say i cu. ft., at a pressure 
of 75 lbs. on the gauge, what will be the pressure indicated if this air is expanded 
to 2 cu. ft.? 

I X (75 + 15) 

P' = = 45 lbs. absolute — 15 = 30 lbs. gauge pressure. 

2 

Example-' A receiver 3 ft. in diameter and 6' ft. long is filled with com 
pressed air which indicates 60 lbs. on the gauge. What will be the pressure if 
this volume of air is enclosed in a receiver 4 ft. in diameter and 12 ft. long? 
Volume of first receiver =: 3- x .7854 x 6 = 42.4 cu. ft. 



I 



r 



PRODUCTION. loi 



X'olume of second receiver = 4^ x .7854 x 12 = 150.8 cu. ft. 
42.4 X (60 + 15) 

7'= = 21.1 lbs. absolute — 15 = 6.1 lbs. gauge pressure. 

150.8 
The same rule applies in calculating volumes. In dealing practically with 
compressed air, we speak of pressure above the atmosphere', but in making calcu- 
lations for volumes serious errors frequently occur because the atmospheric pres- 
sure (15 lbs.) is lost sight of. 

For instance, a cubic foot of air represents about 15 lbs. absolute pressure, 
and if we wish to know what volume this cubic foot will occupy when it is sub- 
jected to a pressure (isothermally) of 60 lbs. per square inch above the atmos- 
phere, we must figure thus: 

I X 15 

(c) V = = 0.20 cu. ft. 

60+15 
Given i cu. ft. of compressed air at 45 lbs. gauge pressure, what volume 
will this air occupy when subjected to a gauge pressure of 60 lbs.? 

I X (45 + 15) 

(d) V = — 0.8 cu. ft. 

60 + IS 
Free Air. — By free air is meant air at atmospheric pressure, which is about 
i'5 lbs. per square inch at sea level. 

Given a volume, say 500 cu. ft., of free air, what volume will this air occupy 
when compressed (isothermally) to 60 lbs. gauge pressure? 

500 X 15 

V = = 100 cu. ft. 

60+15 
Reversing the problem, how much free air is represented by 100 cu. ft. of 
compressed air at 60 lbs. gauge pressure? 

100 X (6a + is) 

V = =: 500 cu. ft. 

15 
Volumes of Free and Compressed Air Furnished by Air Compressors. 
Example, The air cylinder of a compressor is 12 ins. in diam., stroke 18 
ins. What volume of free air will it furnish (theoretical) when running at 120 
revolutions per minute? 120 revolutions represents 360 ft. piston speed per 
minute. 

1 13. 1 X 360 

12" X .7854 = 1 13. 1 area in square inches. == 282.7 cu. ft. free air. 

144 
282.7 X 15 

And by (c) = 56.5 cu. ft. of compressed air at 60 lbs. on gauge. 

60 +15 

A rule by which volumes of compressed air may be approximately deter- 
mined from volumes of free air, is to divide by the number of atmospheres. 



102 



PRODUCTION. 



For instance, 60 lbs. represents 5 atmospheres (absolute) ; 500 cu. ft. of free 
air, divided by 5, equals 100 cu. ft. of compressed air at 60 lbs. gauge pressure. 

As pressures are not always given in even multiples of atmospheres, this 
rule serves only to determine approximate results. 

Reduced Effiency of Air Compressors at Different Altitudes. 

The previous figures are based on the pressure of air at sea level, or 15 lbs., 
(about) per square inch. As air compressors are frequently used at altitudes, it 
is desirable to know the extent to which an increased altitude affects the capacity 
of the compressor. Following are the barometric pressures at different alti- 
tudes : 

Lbe. per 
eq. in. 
J4 mile above sea level 14.02 



Pressure at 


Va 






¥-> 






Va 






I 






iVa 






1/2 






2 



13-33 
12,66 
12.02 
11.42 
10.88 
9.88 



Free air as applied to the volimie of a compressor, or the space traversed 
by the piston, is not affected by change of altitude, but free air when applied to 
pressures either absolute or indicated, and to volumes of compressed air, is modi- 
fied according to the density of the air at corresponding points. 

Example: Required the volume in cu. ft. of compressed air furnished by 
an air compressor when at work one mile above sea level. Also, the volume in cu. 
ft. of free air representing the reduced efficiency of the compressor when at work 
at this altitude. 

Given an air compressor of the following dimensions: Diameter, 12 ins.; 
stroke, 18 ins.; revolutions per minute, 120. 

We have seen by a previous example that this compressor furnishes 282.7 
cu. ft. of free air (theoretical) at sea level, and that this volume represents 56.5 
cu. ft. of compressed air at 60 pounds on the gauge. If this compressor is used 
at an altitude of one mile above the sea, what volume of compressed air will it 
furnish at 60 pounds on the gauge, the speed remaining the same ? 

Free air furnished by compressor, 282,7 cu. ft. 

Barometric pressure at altitudes of one mile, 12.02 lbs., then by (c) sub- 
stituting the reduced barometric pressure we have : 
282.7 X 12.02 

y = = 47.18 cu. ft. at 60 lbs. on gauge. 

60 + 12.02 
And if it is desired to know how many cu. ft. of free air at sea level are repre- 
sented by 47.18 cu. ft. of compressed air at 60 lbs. we have by 
47.18 x(6o + 15) 

{d) V = = 235,9 cu. ft. of free air at sea level, and 282.7 — 

15 



t 



PRODUCTION. 103 

235.9 = 46.8 cu. ft. of free air, representing the reduced efficiency of the compres- 
sor when used at altitude of one mile. 

In practice, approximate determinations of the reduced efficiency of air 
compressors are made by deducting the percentage of difference between the 
barometric pressures of the respective latitudes. 
The volume at sea level being i, that at 

1/4 mile above sea level will be 7% less 

K " " " " " " 11% " 

Y^ " " " " " " 16% " 

1 " " " " " " 20% " 

i^ " " " " " " 24% " 

iH " " " " " " ..28% " 

2 " " " " " " 34% " 

W. L. SAUNDERS. 



VOLUMETRIC EFFICIENCY IN AIR COMPRESSOR PRACTICE. 

Volumetric efficiency in air compressor practice is a subject which has been 
neglected by builders of machines and by the public generally. Catalogues of air 
compressors, with great unanimity, claim about 100 per cent, volumetric efficiency : 
In other words, the capacity of an air compressor in free air compressed is meas- 
ured by the piston displacement, the theoretical volume of the cylinder being 
taken at a certain piston speed. It is plain that no machine however perfect will 
deliver as much air as this, because clearance, leakage, etc., must be taken into 
account. So long as makers are not required to give a guarantee, it is well enough 
to base figures upon the piston displacement as this gives a base line for compari- 
son. Recent improvements in air compressors have been in the line of reduced 
volumetric losses. The old DuBois-Francois type of compressor which used water 
in the air cylinder for the purpose of cooling and filling the clearance spaces made 
slow speed necessary and the abandonment of water injection followed closely 
the development of improved forms of valves reducing clearance spaces to a mini- 
mum. The theoretical volumetric efficiency of an air compressor is also reduced in 
actual practice because it is not possible to fill the cylinder at atmospheric pressure 
except perhaps at very slow speeds. Any light indicator spring will show from 
one to three pounds vacuum in an air cylinder when used at its normal piston 
speed. The higher the speed, the greater this vacuum will be. A partial vacuum 
is necessary in any case to get the air in the cylinder, even with a perfectly free 
mechanically moved inlet valve of large area. In compound compressors the pres- 
sure line in the initial cylinder usually shows a partial vacuum greater in propor- 
tion as the cylinder is larger and usually more noticeable than in the ordinary 
indicator card because of the use of the light spring. Actual volumetric efficien- 
cies vary from 85 per cent, in small poppet valve compressors to 97 per cent, with 
long stroke Corliss machines. In the latter this high efficiency cannot be main- 
tained at a piston speed of over 350 feet per minute. 97% volumetric efficiency 
is obtained in high class Corliss compressors of the best type. The usual straight 
line or pony type of compressor which is designed to run at high speed does not 



I04 PRODUCTION. 

g'ive a high volumetric efficiency, because of the inertia of the discharge valves 
which does not permit them to seat quick enough to prevent some of the com- 
pressed air from getting back into the cylinder on the return stroke. This type of 
machine furnished by makers of first-class air compressors working under the 
normal conditions will give about 90 per cent, volumetric efficiency. A compressor 
of this type with an air cylinder say 20" in diameter by 24" stroke, and which 
has a rated piston speed of 375 feet per minute, if run at only 250 feet per minute, 
will show a volumetric efficiency of 95 per cent, and this will be reduced in pro- 
portion as the speed is increased. These figures are based on perfectly tight valves 
and piston, a condition which should exist in machines of the first class when in 
the hands of good engineers. 



RELATIVE EFFICIENCIES OF A COMPRESSED AIR PLANT DUE TO 
DIFFERENCE OF LEVEL ABOVE AND BELOW SEA LEVEL. 

The atmosphere surrounding the earth forms a layer extending about 45 
miles in height, and being ponderable and very elastic, its density will vary with 
the height. 

At the sea level the weight of a column of atmospheric air one square 
inch in area will balance a column of mercury 30" high one square inch in area, 
and corresponds to a pressure of 14.7 pounds per square inch. 

Now, if we take the sea level as a basis for comparison as to the density or 
weight per cubic foot, we will find that the higher up we go the more rarified the 
air becomes, due to diminished height of the atmosphere above us, and by 
descending the shaft of a mine the contrary effect takes place. However, in the 
mine or in any level below the sea this contraction of the air is counteracted by 
the increasing temperature as we approach the centre of the earth. 

From observations taken at different parts of the world this increase has 
been found to average I deg. F. for every 61 ft. depth. The temperature also 
changes with increasing altitudes. However, since there is no uniform change 
in temperature throughout the world for points at the same elevation, it will be 
hard to estimate this effect generally, and in order to show this influence of tem- 
perature and pressure, we must assume some specific case. 

A motor using compressed air at full stroke and at 80 pounds per square 
inch, will require at any level either above or below the sea level — 

229.5 

= cu. ft. free air 



c--^) 



per minute per I. H. P. 

where pa = atmospheric pressure 

P2 = absolute working pressure. 

From a study of this formula it Avill readily be seen that as the atmospheric 
pressure diminishes, the cu. ft. free air required per h. p. will increase, and con- 
sequently a larger compressor will be required at an elevation than at sea level to 
enable the motor to do the same amount of work in a given time. 



PRODUCTION. 



104a 



b § ^ 5 -s 




<?. c/e<» /«^e / 



FIG. 32a. 

Volumetric efficiency of a compressed air plant (delivering air at a 

GAUGE pressure OF 80 LHS. PER SQ. IN.) DUE TO DIFFERENCE OF LEVEL ABOVE AND 
BELOW SEA LEVEL. AIR USED IN MOTOR AT FULL STROKE. EFFICIENCY AT SEA LEVEL 
TAKEN AS 100 PER CENT. 



io4b 



PRODUCTION. 



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FIG. 32b. 



Curves showing ter cent, of additional power required in an air com- 
pressor TO perform a given amount of work at different altitudes (with a 

working pressure of 80 LP.S. PER SQ. IN.). SEA LEVEL TAKEN AS UNITY. AIR USED 
IN MOTOR AT FULL STROKE. 



PRODUCTION. 105 

The relative efficiencies due to change of volume have been plotted in the 
curves shown on page 104a. Both temperature and difference in levels above and 
below sea level have been taken account of, so that by reference to this chart it 
will be an easy matter to select an air compressor of sufficient capacity to supply 
a motor with an equivalent volume of air, no matter where it may be located 
provided temperature changes and working pressure are the same as assumed 
in the curves. 

Thus, given an altitude of 6,000 ft. above sea level, and provided the tem- 
perature at this level is the same as at the sea level, then by referring to the 
chart and reading along the 6,000 ft. level li^ie until we intersect the constant 
temperature curve, we will find by reading across to the right that the efficiency 
of an air compressor at this altitude is but 81.5 per cent, of its efficiency at sea 
level; and in order to produce the same efficiency, the free air capacity of com- 
pressor will have to be increased 18.5 per cent. When the temperature of the air 
changes proportionately from 62 deg. F. at sea level to 32 deg. F. at 10,000 ft. 
altitude, the efficiency in the case we have assumed will be 84.2 per cent, (as will 
be seen from the curves). 

The efficiency at 2,000 ft. below the sea would be 105.5 per cent, provided 
the temperature was constant (62 deg. F.) ; however, the rise in temperature of i 
deg. F, for every 61 ft. depth, exactly offsets the gain which might be effected 
by increased density, and therefore the efficiency is practically constant for all 
depths below sea level. 

The change in volume due to different altitudes also effects the power 
required to perform a given amount of work. The mean effective pressure per 
cubic foot is less at an altitude than at sea level, but the number of cubic 
feet required to produce the same effect at an altitude as at the sea level is 
more, and the product of the two (M. E. P. x Vol. = power expended), is 
greater. Curves on page 104b show the relative effect for the different altitudes 
and different temperatures. Thus at 6,000 ft. and temperature at 62 deg. F. 
(same as assumed at sea level), the increase in power for a given effect will be 
13-30 per cent. If the temperature changes proportionately from 62 deg. F. at 
sea level to 32 deg. F. at 10,000 ft. altitude, the increase in power will be but 8.8 
per cent. The difference between both curves shows the benefit obtained from 
cold air. F. c. weber. 



EXPERIMENTAL MECHANICS. 



Method of Calculating and Recording the Results of the Experiments Made 
During the Supplementary Term. 

BY PROF. D. S. JACOBUS, '84. 

Table XVI. 

TEST OF AIR COMPRESSOR. 

[Bore of air cylinder 

1. Dimensions in inches and clear- J Bore of steam cylinder 

ance. ) Stroke of both pistons. 



8. Revolutions per minute. 



(.Clearance of air cylinder in per cent. 



io6 



PRODUCTION. 



Initial entering compressor 

Piual in deliveiy pipe two feet from compressor. 
Initial 



Final when drawn from separator in delivery pipe. 



3. Temperature of air in degrees 

Fahr 

4. Tempeiature of jacket water in 

degrees Fahr I Final 

5. Temperature of water injected I Initial 

in degrees Fahr . 

6. Weight of jacket water per minute iq p mnds 

7. Weight of water injected into air cylinder m pounds 

8. Barometric pressure in inches of mercury 

9. Indicated horse-power of air cylinder , 

10. Indicated horse-power of steam cylinder ...... .^ 

11. Per cent, of indicated power of steam cylinder lost m fraction. . .... . . .^^ 

12. Value of y in the equation pv v = constant for the air compression curve. 

13. Weight of air compressed per minute calculated from the indicator card, m pounds 

METHODS TO BE EMPLOYED IN CALCULATING THE RESULTS. 

Items I to 8 contain the data observed during the test. 
9. Same as item 13 of Engine Test, Table III*, except that there is no factor of 
2 in the numerator, because the compressor is single acting. 

10. Same as item 13 of Engine Test, Table III*. 

11. ] (Item 10— item 9) -^ item 10 | X 100. 

12. An indicator card of the air compressor is shown in Fig. 33. 

If the temperature of the air had remained constant during compres- 
sion then the curve of compression AB would be isothermal and the prod- 
uct p V oi the pressure and the volume would be constant. The air is not, 




FIG. 33. — INDICATOR CARD OF THE AIR COMPRESSOR. 



however, thoroughly cooled during compression and the equation becomes 
pvy = C= a constant. 

Lay off the lines of zero pressure and volume EF and ED in Fig. i. If 
the pressure and volume at A be designated by the subscript a and that 
at B by the subscript b, we have 



V 

PaK 



C, and Pf^ v^ = C. 



* Refers to set of Tables used at Steven's Institute. 



r 



PRODUCTION. 107 



From these equations we have 



I =Pb ^i' ^^^^ ^'^ic^ log- Pa + y ^^S- % = log- Pb+ y log- H and 



y = log.^-^lo^.^ (A) 

Pa ^ Vb 

The values of ^, or the ratio of pressures, and the ratio of volumes ^ 

Pa Vb 

will be the same no matter what scale is employed in measuring pa. pb, 

Va, Vb] hence we may measure the distance on the indicator cards in inches 
and substitute in equation (A). 
13. Determine the net volume swept through by the piston per revolution in 
cubic feet and multiply by the number of revolutions per minute, in order 
to determine the volume of air compressed per minute for full displace- 
ment; multiply this by the ratio of the distance HA to the length of the 
indicator card to allow for the effect of clearance. The volume of air com- 
pressed per minute multiplied by the density at the pressure AF, or that cor- 
responding to the pressure of the atmosphere, will give the weight com- 
pressed per minute. To find the weight of one cubic foot of air at the 
pressure shown by the barometer and the temperature of the air on entering 
the compressor, make use of the table given on page 381 of "Kent's Me- 
chanical Engineers' Pocket Book." The density corresponding to the tem- 
perature given in this table is multiplied by the factor, 

b -^ 30, 
where b is the barometric pressure in inches of mercury (not corrected to 
32° Fahr.), or more exactly by the factor, 

b' -r- 29.92, 
where &' is the barometric pressure corrected to 32° Fahr. 
It is assumed in this computation that the temperature of the air in the 
cylinder, just before compression, is that of the external air. Usually this is not 
the case as the air is heated during admission, and there is an increase in volume, 
and consequently a loss of capacity due to this cause. In experiments made by 
Messrs. Cause and Post, Class of '91, this loss was found to be about 10 to 15 per 
cent. — Stevens' Indicator. 



THE USE OF WATER POWERS BY DIRECT AIR COMPRESSION.* 

Probably one of the oldest applications of the use of water power to the 
wants of man was a form of hydraulic air compressor which operated as an 
entrainment apparatus, and is the well-known water bellows or trompe of the 
Catalan forges. 

This apparatus, briefly described, consisted of a bamboo pole disposed at 
a slight inclination from the perpendicular, into the upper end of which a stream 
of water was led, entraining air with it in its downward passage. The lower end 
of this bamboo pole was introduced into a bag made of the skin of some animal, 
the air being allowed to escape from the water into the upper part of the bag, 



*The movement toward fuller utilization of the yet unrealized water resources o*" the world is one 
which is constantly quickening. With greater use comes larger study of adaptation of machinery and 
methods of water-power development and transmission. The peculiar means described by Mr. Webber 
bas more than a passing Interest.— .Sailors' Engineering Magazine. 



lo8 



t>RODUCTION. 



from whence it was led by pipes or tuyeres to the forge, the water being allowed 
to escape from the lower edge of the bag. From this original device a great many 
improvments have been worked out, and besides this, a number of other forms 
of hydraulic air compressors, or of compressors using other liquids for com- 
pressing air or other gases, have been designed. > 

A very simple form 'is a displacement apparatus,* consisting of a water 
reservoir and two air chambers of about three times 'the capacity of the water 
chamber. Water is led into the reservoir, compressing the air contained in it into 
the two chambers and giving a pressure of about 1.6 atmospheres, 

Siemens invented an apparatus on the principle of the steam injector, but 
the use of this was confined principally to the production of a vacuum; it is used 




FIG. 34. — THE MAGOG DAM AT HIGH WATER. 



to Operate the pneumatic dispatch tubes in London. It has also been used for 
blast purposes in Siemens' furnaces and in sugar works. 

Another quite ingenious device, shown in a patent granted to W. L. Howe, 
consists of two flat plates enclosing an air space from which a pipe leads to the 
atmosphere. The upper plate is perforated with conical holes, the smaller end 
being adjacent to the air-space between the two plates. Directly opposite the 
apertures of the upper plate are corresponding conical apertures in the lower 
plate, with the smaller end of the aperture next the air space, the lower and 
larger part of the conical openings being prolonged by tubes; the upper plate is 
kept under a head of water; the water jet, passing across the thin air-space 
referred to, draws in the air through the large air pipe and compresses it through 
the smaller orifices. 

Another device using a somewhat similar principle was invented by M. 
Romillyt and consists of a conical tube attached to an air reservoir by its larger 



♦ Appleton'a Cyclopedia of Applied Mecbanice, fig. 138, page 37. 
t Appleton's Cyclopedia of Applied Mechanics, fig. 139, page 37. 



PRODUCTION. 109 

end, and having a check valve interposed in the passage so as to prevent the air 
from escaping. Water is then injected into the smaller end of this conical tube 
through an ajutage in the form of a liquid vein at a given pressure, which en- 
trains the air with it and causes it to be compressed in the reservoir. But the 
apparatus just described did not really employ the same methods as those used 
in the old trompe. One of the first inventions carrying out this idea was made 
by Mr. Frizell, of Boston, Mass. His invention made use of an inverted syphon 
having quite a little horizontal run between the two legs. A stream of water 
was led into the upper end of the longer leg, and at the top of the horizontal run 
between the two legs of the syphon was provided an enlarged chamber in which 
the air would separate from the water, the water being then led off from the 
lower part of this air chamber and passed off through the shorter leg of the 
syphon, the pressure of the air accumulated in the air chamber being therefore 
due to the height of water maintained in the shorter leg of the syphon. This 
application of carrying upward the water, after the air was separated from it, 
so as to produce a considerable pressure upon the air, seems to have been original 
with Mr. Frizell, and in this feature his device differs from the old trompe. 

Mr. Frizell made two working models of this type of apparatus. In the 
first one the legs of the syphon were 3 inches in diameter, the head of water 
being 25 inches, and an efficiency of 26^ per cent, was obtained. A larger 
apparatus was then constructed at the Falls of St. Anthony, on the Mississippi 
River, a few miles above St. Paul ; the longer leg of the syphon in this plant was 
15 inches by 30 inches and the short leg of the syphon 24 inches by 48 inches in 
section; the height of water above the air chamber was 29 feet. The head in 
feet varied from .98 to 5.2, the first head being just sufficient to cause a flow 
through the pipes. The working head varied from 2.54 feet to 5.02 feet and the 
efficiency from 40.4 per cent, to 50.7 per cent., the quantity of water in these cases 
varying from 5.92 to 11.89 cubic feet per second. 

Mr. Frizell estimates from the experiments he has made that with a shaft 
10 feet in diameter, a depth of 120 feet, and a fall of 15 feet, the efficiency would 
be 76 per cent., and with a head of 30 feet and a fall of 230 feet, the efficiency 
would be 81 per cent. 

Another device, differing somewhat from that of Mr. Frizell, was invented 
by A, Balochi and A. Krahnass in 1885, and consisted of a syphon carrying water 
from an upper reservoir down to another reservoir situated at a lower level, the 
lower end of the syphon being projected through an inverted vessel placed nearly 
at the bottom of the second reservoir. Just beyond the bend of the syphon, and 
in line with the vertical axis of the longer leg thereof, was an air pipe projecting 
into the descending column of water, thus entraining the air with the descending 
column, and carrying it down into the inverted chamber, where the air escaped 
from the top and the water passed out from the bottom of the inverted vessel 
into the lower chamber. This also produced pressure on the air in the top of 
the inverted chamber, due to the height of the water column upon it. 



no 



PRODUCTION. 



Another device, patented by Arthur in 1888, differs from the last in having 
a stream of water led directly into the top of the vertical pipe. Inserted into 
the mouth of this pipe was a double cylindrical cone, making an annular air 
passage surrounding the mouth into which the water was delivered. The water, 
after passing through the upper cone and there being compressed and its velocity 
increased, then passed into the inverted cone, where the velocity was somewhat 
decreased and the water became more diffused. This lower cone was perforated 
with holes opening into the annular air chamber previously described, causing air 
to be entrained with the falling water. Inside of this down-flow pipe was a ver- 




FIG. 35. — COMPRESSOR HEAD TANK AND WEIR. 
The air compressor is blowing off. 



tical delivery pipe for the compressed air, having its lower end enlarged and 
open at the bottom. Projecting upward into this enlarged air-delivery pipe was 
a water escape pipe through which the water passed after having parted with the 
air. This escape pipe was in the form of an inverted syphon and maintained 
a pressure on the air in the delivery pipe, due to the elevation of the water at its 
discharge point above the air line in the large end of the delivery pipe. 

A number of other patents on apparatus of this type were issued 
to Charles H. Taylor, Nos. 543,4io; 543,41 1; 543,412, July 23, 1895; his invention 
consisted principally of a down-flow passage having an enlarged chamber at the 
bottom and an enlarged tank at the top. A series of small air pipes were pro- 
jected into the mouth of the water inlet from the large chamber at the upper end 



PRODUCTION. 



Ill 



of the vertically descending passage, so as to cause a number of small jets of air 
to be entrained by the water, Taylor seemingly having been the first one to intro- 
duce the plan of dividing the air inlets into multiplicity of smaller apertures 
evenly distributed over the area of the water inlet. 

Taylor at first seems to have attempted to utilize centrifugal action in 
causing the separation of the air and water in the large chamber at the bottom 
of the compressed column, but afterward abandoned this scheme and used, in- 
stead, forms of deflected plates in combination with a gradually enlarging section 
of the lower end of the down-flow column in order to decrease the velocity of 
the air and water and cause partial separation to take place, and also using 




FIG. 36.— VIEW TAKEN BY POINTING THE CAMERA DIRECTLY DOWNWARD OVER THE 

EDGE OF THE WEIR. 

The clouds are made by the finely-divided particles of air carried in suppension. In the limpid 
Maefog water these may be traced 40 or 50 feet below the weir. 



the deflector plates to cause the water to change its direction of flow, evidently 
with the idea that the air would escape more readily. 

The latter improvements on this device have been in the method of intro- 
ducing the air into the mouth of the downwardly flowing water column, so as to 
insure the largest proportion of air being taken down with the water, and in 
methods of decreasing the velocity of the combined air and water at the bottom 
of the descending column, causing the water to part more readily with the air, 
the water then passing out at the bottom of the enlarged chamber into an ascend- 



112 PRODUCTION. 

ing shaft, maintaining upon the air a pressure due to the height of water in the 
uptake, the air being led off from the top of the enlarged chamber by means of a 
pipe. 

The first one of these compressors on the Taylor principle was installed 
at Magog, Quebec, to furnish power for the print works of the Dominion Cotton 
Mills Company. The head of water is 22 feet; the down-flow pipe is 44 inches 
in diameter, and extends downward through a vertical shaft 10 feet in section and 
128 feet deep. At the bottom of the shaft the compressor pipe enters a large 
tank 17 feet in diameter and 10 feet high, which is known as the air chamber 
and separator. 

A series of very careful tests on this plant demonstrated that out of a gross 
water horse power of 158.1, 11 1.7 horse power of effective work in compressing 
air has been accomplished, giving, therefore, an efficiency of 71 per cent. It is 
found that the air after compression shows a very considerable decrease in 
moisture from that of the air entering the compressor, although in contact with 
the water all the time. This is probably due to the moisture in the bubble of 
air being pressed or squeezed out to its surface and then absorbed by the sur- 
rounding water. The air is compressed at the temperature of the surrounding 
water and the compression is isothermal. Owing to these facts, there is no loss 
by heat of compression and again by radiation, in using the air, and there is a 
practical result which is of more importance ; the hydraulically-compressed air can 
be expanded down to a temperature much below the freezing point, while atmos- 
pheric air with its usual amount of moisture, mechanically compressed, cannot 
be uSed at all, owing to the freezing up of the exhaust passages of the motoi m 
which the attempt to use it is being made. 

The accompanying photographs give an idea of the extent of the plant and 
of the volume of water used. The last one, showing the air carried in suspen- 
sion, is especially interesting. The air cloud may be traced in the water quite 
as distinctly as it is shown in the photograph, for 40 or 50 feet below the weir. 

William O. Webber, 
in The Engineering Magazine. 



RATIOS OF AREAS OF INLET AND OUTLET VALVES TO THAT OF 
THE AIR CYLINDER. 

In an air compressor what are the correct ratios of areas of inlet and 
outlet valves to that of the air cylinder?— Aj ax, Baltimore, Md. 

There is no such thing as correct ratios in cases of this character. We 
can only say what seems to be the most common and approved practice, or what 
experience has demonstrated to be, upon the whole, the best. Valve areas on a 
compressor depend ' -gely upon the style of valve employed, that is, whether iht 



PRODUCTION. 113 

opening is one concentrated area, and also whether the valve is held open to get 
all this area throughout the stroke. Roughly speaking, about 5,000 feet per 
minute velocity for the air passing the valve gives good results, a slow running 
machine, that is, one having low piston speed, hence requiring a smaller valve 
area than a fast running machine. In compressors using the "piston inlet" 
valve and having from 300 to 350 feet piston speed, the inlet area is from 5 to 6 
per cent., this area, however, being concentrated and positive for the whole 
length of the stroke. In this case, the velocity of the air is 7,000 feet per minute, 
but good results are shown. On large compressors, where the steam cylinders 
are of the Corliss type, and the piston speeds are as high as 500 to 600 feet per 
minute, the inlet areas, with the same type of valve as before, range from 6^ 
to 7 per cent., and the discharge areas (poppet valves) from 10 to 12 per cent., 
giving about the same velocity in the air passages as with the slower machines. 
On machines having poppet valves all around probably 12 per cent, of area is 
necessary, as machines with but from 7 to 10 per cent, area have shown con- 
siderable vacuum on the inlet, the springs tending to hold the valves partially 
closed and reducing the practical area. About 10 per cent, area for both the 
inlet and discharge valves should be sufficient for almost any good style of 
valves and for piston speeds not exceeding 400 feet per minute. The area of the 
discharge valves should not be less than that of the inlet valves, as, although 
the volume of air passing the discharge valves is, of course, much less than that 
passing the inlet valves, the time allowed for the passage is also proportionately 
less. While the inlet valves are open, or should be, during the whole of the 
intake stroke, the discharge valves can be open only for one- fourth or fifth, ^ or 
other small portion of the stroke, according to the pressure. For most of the 
above, we are indebted to Mr. William Prellwitz, M. E., chief draftsman of the 
Ingersoll-Sergeant Drill Company, Easton, Pa., and it is based upon the practice 
and experience of that company. — Am. Mack. 



CURVES SHOWING TEMPERATURE OF AIR DURING 
COMPRESSION. 

Two curves are shown in the diagram, the ordinates representing pressures 
and the abscissae volumes. The curve drawn in full line shows the compression 
of air without any cooling effect, while the one drawn in dotted line shows the 
compression of air at a constant temperature. The former is the adiabatic curve 
whose equation is 

1.40S 






the latter is the isothermal curve and has the equation 

/) X z/ = constant. 



114 



PRODUCTION. 



In single stage compression the power required for compression may be 
calculated without taking into consideration the slight cooling effect due to the 
water jacket; the air will, therefore, be assumed to follow the adiabatic curve. 

Starting at the left the first column of figures gives the gauge pressure for 
each horizontal line. The second column gives the Indicated Mean Effective 




FIG. Z7- 

Pressures. These were calculated by a formula which was derived in the manner 
shown in figures y? and 39. 

The area of the shaded portion of the diagram Fig. yj, is 



P2V1 — prV^ 



1.408 — I 



= 2.45 (P2V2—P1VO 



In order to get the area of the shaded portion of the diagram Fig. 39, which 
represents the work done during the stroke of the air piston, we have to add 



this makes the 



p>Z'2 — piVi 

Area = 3.45 {piVz—piVr) 
Dividing this by Vi will give us the 

I. M. E.=3-45 (i?2~— i?i) formula (i) 

The third column gives the Horse Power required to compress one cubi( 
foot of free air, measured by the displacement of the air piston. 
When /> = I. M. E. pressure in lbs. per sq. in. 
a =■ area of air piston in sq. in. 
P = piston speed in feet per min. 
D = displacement in cubic feet per min. 



then 



aX p X P 



IT. P.— 



33000 
a X P 



D=- 



144 



PRODUCTION. 



115 



Two 5tA«E C0l-'TPTPt«>S«ON 




FIG. 38, — AIR DIAGRAAJ, 



ii6 



PRODUCTION 



and Ihe Horse Power required per cit. ft. 

H. P. aXpXP 144 
• = X 



D 



33000 



aXP 



II. P. per cii. ft, = .00437 P formula (2) 



The four columns at the left give similar data for. two-stage compression. 
The I. M. E. pressures were calculated for air partly cooled by taking a mean 
between the pressures obtained by adiabatic and isothermal compressions. 

The ratios of cylinders given will distribute the load evenly among the two 




FIG. 39. 

cylinders ; they may, of course, for practical reasons, be varied considerably with- 
out impairing the efficiency of the machine. 

Formula (i) for the I. M. E. pressure will, for the two extreme cases 
pi =^ and pi = pi, 
give the value I. M. E. = 0. 

It is evident that between these two values there must be a maximum. This 
will be obtained when 

pi =^ .304 p2 formula (3) 



This formula will be found useful in calculatmg gas compressors where the 
gas comes in under a head but is expected to drop to atmospheric pressure in the 
future. The driving mechanism of such a compressor should be calculated for 
this maximum. 



HEAT REQUIRED TO RAISE THE TEMPERATURE OF AIR. 

Air, in common with all other gaseous substances, possesses the property of 
rcquirmg various amounts of heat to raise its temperature through a given range, 
accordmg to the circumstances under which the heat is applied. This point is of 



PRODUCTION. 



117 



so much importance that an entire article would be needed to elucidate it prop- 
erly; but for the present it will be sufficient to say that the "specific heat" here 
given for air (/. e., the number 0.238) assumes that the air that is to be heated 
is constantly at atmospheric pressure — that is, it assumes that throughout the 
entire process of heating, the air is never exposed to a pressure that is sensibly 
higher or lower than that of the atmosphere. This condition is often fulfilled in 
practice, and the specific heat here given will therefore be found useful. When 
other conditions prevail, however, some different value must be used for the 
specific heat — a value that can be determined only when the new conditions are 
fully given. 

In calculating the number of heat units required to warm a given mass of 
air from one temperature to another one, we proceed precisely as we did in the 
case of iron ; that is, we first calculate the heat that would be absorbed by an 
equal weight of water, and then we multiply by 0.238, which is the "specific heat" 

TABLE II. — WEIGHT OF A CUBIC FOOT OF AIR, AT ATMOSPHERIC PRESSURE 

(.0 to 600° R). 



^ 


a • 


p 


'^■^ 


S 


S3 . 


0) 


03 . 


__^ 










«i-i 0'^ 


^ 

3 


♦J ^^ 




0^ 




<o 




00=" 




"o 0^ 


S3 tH 


^fa-g 


"S u 




1 5* 


-^"S 


1 s 


-^1 


I'S 


III 






Ns 


X3 5 


l^'5 


^ 3 


^•s 


^5^ 


l^'S 


^6- 


e'S 


^0- 


^•s 


^6- 


0° 


.0864 


lOO'' 


.0710 


200° 


.0603 


300° 


.0523 


10 


.0846 


no 


.0698 


210 


.0594 


320 


.0510 


30 


.0828 


120 


.0686 


220 


.0585 


340 


.0497 


30 


.0811 


130 


.0674 


230 


.0576 


360 


.0485 


40 


.0795 


140 


.0663 


240 


.0568 


380 


.0474 


50 


.0780 


150 


.0652 


250 


.0560 


400 


.0463 


60 


.0765 


160 


.0641 


260 


.0552 


450 


.0437 


70 


.0750 


170 


.0631 


270 


.0545 


500 


.0414 


80 


.0736 


180 


.0621 


280 


.0538 


550 


.0394 


90 


.0723 


190 


.0612 


290 


.0531 


600 


.0376 



of air (at constant pressure). Air is usually estimated in cubic feet instead of in 
pounds, because it is much easier to measure its volume than its weight. If, 
therefore, we have a certain volume of air given, and we wish to find out how 
much heat will be required to warm it through a certain range of temperature, 
we must first find out how much it weighs. To accomplish this without too much 
labor we may make use of the accompanying table, which gives the weight (in 
pounds) of a cubic foot of air at various temperatures, but always at atmospheric 
pressure. 

To illustrate the use of this table, and the method of calculating the number 
of heat units required to heat a given mass of air through a given range of tem- 
perature, let us take the following problem : It is proposed to heat a mass of air 



ii8 PRODUCTION. 

from 50° Fahr., to 110° Fahr., by passing it, at atmospheric pressure, over a coil 
of steam pipe. The proposed mass of air, when measured at 50° Fahr., occupies 
500,000 cubic feet. How many heat units will be required? To solve this prob- 
lem we first find out how much the air zveighs. By referring to the table we see 
that one cubic foot of air, at 50° Fahr. and atmospheric pressure, weighs 0.078 of 
a pound. Hence 500,000 cubic feet (measured under these same conditions) will 
weigh 

500,000 X 0.078 = 39,000 pounds. 

Having found the weight of the air in this manner, we proceed to calculate the 
amount of heat required by first figuring it as though the substance to be heated 
were water. Thus the initial temperature is 50° and the final temperature is 110°, 
and the difference between these is 110° — 50° = 60°, which is the number of 
degrees through which the temperature of the mass must be raised. There being 
39,000 pounds of the air, we should have to communicate 

39,000 X 60 = 2,340,000 heat units 

to it, if it were zvater, in order to heat it from 50° to no". To take account of 
the fact that the substance is air instead of water, we multiply this result by 0.238 
(the "specific heat" of air at constant pressure), just as in the case of iron we 
multiplied by 0.117. Thus we have 

2.340,000 X 0.238 = 556,920 heat units, 

which is the quantity of heat that would be required to raise 500,000 cubic feet of 
air from 50° to 110°, the air being measured at 50° Fahr., and its pressure remain- 
ing equal to that of the surrounding atmosphere throughout the operation. 



Denver, Nov. 21, 1898. 
Editor Compressed Air : 

I have been investigating the question of the development of heat in com- 
pressing air at low pressures, and have failed to find any table which gives accu- 
rately the heat developed. 

I will be very much obliged if you know of any table which will give the 
following information. If you will send it to me or advise me where I can get 
it, or if you can give me the figures in this particular item, I will be very much 
indebted to you. 

What I want to know is this : Given 10 cubic ft. of air at 32 degs. F. and 
atmospheric pressure, how much pressure will be necessary to raise the tempera- 
ture of this air to 33 degs., and how much reduction in the volume of the 10 ft, 
will there be at this pressure? 

Thanking you in advance for any trouble you may take in this matter, I am, 
Yours very truly, mining engineer. 



PRODUCTION. 119 

The diagram shown on page 19 of this book (Fig. 2), and also 
in Compressed Air, Vol. I., No. 3, page 7, shows the relative difference in vol- 
umes, pressures and temperatures during the compression of air. This diagram 
does not give the difference as close as i deg., but it may serve your purpose; 
if not, we would refer you to Shones' tables, printed in the Scientific American 
Supplement, No. 279, and prepared by Isaac Shone, C. E. We know of no tables 
closer than these, which are for differences of one pound pressure. They may 
be readily interpolated for fractions of a pound equal to i deg. rise in tempera- 
ture. The only formula applicable to the case is that of Dubois and Rontgen, 
which was used by Shone in computing the tables published in the Scientific 
American Supplement, No. 279, to which we have referred. The formula is for 
differences of temperature due to compression by compression or volume differ- 
ences. It would have to be inverted for differences of pressure or volume due to 
temperature. The inversion is not stated in the books, but can be done with some 
experimental computation. 



The formula is : 



-P^°-"9x 461.2 + T = t, 



in which p is atmospheric pressure=i4.7 ; P=pressure of compression, which for 
your case we assume as 14.8, or one-tenth pound advance in pressure; 461.2= 
absolute zero F. and T==temperature above zero F., or 32 deg., as you suggest; 
t=temperature of compression. The 0.29 is the logarithmic exponent, for which 
the computation must be logarithmic. 

Then 24:8 0.29 ^^^^_^,_^^^o^t and 
14.7 

14.8 = log. 1. 1 70262 
14.7 = log. 1.167317 



Substract 0.002945 
Multiply by exponent 0.29 



0.00085405 
Add log. 493.2 = 2.693023 



2.69387705 



Log. number 494.19 

Subtract 493- 20 

.99*^ rise in temperature. 

You will notice by an examination of Shone's table that an interpolation 
can be made that will answer all practical purposes for low pressures, and with 
care may be made for any pressure within the scope of that table. For low pres- 



I20 



PRODUCTION. 



sures i-io of a pound pressure, of volume, very nearly corresponds with i deg. F. 
difference of temperature. 



Compressed Air: 
Sirs : — 

The table for per cent, of work lost due to heat of compression, in the July 
number, may be criticised by your readers for stating the per cent, of loss in some 
cases greater than ioo%. 

It appears from results that the work lost is stated in terms of isothermal 
compression, but since it is more practical to state the loss in per cent, of adiabatic 
compression, I suggest reference be made to table in Vol. I., No. 4. 

I think that I am responsible for both tables given, and consider the table 
in Vol. I. the more intelligent of the two; and make this suggestion so that the 
man who thinks he has found a big mistake, i. e., in having a loss greater than 
the actual work done, can use the other formula. Yours, truly, 

F. C. Weber. 
New York, July 22, '98. 



The table published in our July number is correct, but that it may not be 
misunderstood we have asked Mr. Weber to further illustrate this important 
point in air compression. 



TABLE 12. 



-DELIVERED HORSE POWER PFR 100 CU. FT. FREE AIR COMPRESSED FROM 
ATMOSPHERIC TO GAUGE PRESSURE. 



Gauge 

Pressure 

IbB. perQ' 



One Stage 

Compression 

Adiabatic. 



Isothermal 
Compression. 



Difference 

between 

Adiabatic and 

Isothermal. 



% of work 

lost in 

terms of 

Isothermal 

Compression. 



% of work 

lost in 

terras of 

Adiabatic 

Compression. 



60 


13.41 


10.32 


3.09 


30. % 


23. % 


80 


15.92 


11.90 


4.02 


34. 


25.26 


100 


18 10 


13.15 


4.95 


38. 


27.58 


200 


26.20 


17.20 


9.00 


52.35 


34.40 


400 


36. 


21.35 


14.65 


68.60 


40.75 


600 


43.20 


23.90 


19.30 


83.75 


44.60 


800 


48.80 


25.70 


23.10 


90. 


47.40 


1000 


53.50 


27.20 


26.30 


96.80 


49.20 


1200 


58.50 


28.35 


30.15 


106.15 


51.60 


1400 


61.20 


29.40 


31.80 


108. 


52. 


1600 


64.30 


30.10 


34.20 


110. 


53.3 


1800 


66.80 


30.80 


36.00 


116.80 


54. 


2000 


69.80 


31.50 


38.30 


121.70 


54.8 










A. 


B 



PRODUCTION. i2t 

When air is compressed in one stage to a pressure of 2,000 pounds per 
square inch, more power (theoretically) may be consumed in overcoming resist- 
ance due to the heat of compression, than is required to compress the air isother- 
mally hence the importance of stage compression and inter-cooling when dealing 
with high pressures. This point is clearly brought out by Mr. Weber in the fol- 
lowing interesting figures. — Ed. 

Interpretation of tables "A" and "B." 

Neglect all friction losses. 

Consider the case of compressing 100 cu. ft. free air to 2,000 lbs. gauge pres- 
sure. 

To do this work in a one stage compressor will require 69.8 H. P. 

Of this 69.8 H. P. 38.3 H. P. which is due to the heat of compression, will 
be lost (usually) due to radiation, before the air reaches the motor. 

Table "A" expresses this loss in per cent, of the power available at the 
motor, which in this case is 1,216 times the available power, or it is 121.6% of the 
isothermal Horse Power of compression. 

Table "B" expresses this loss in per cent, of the power actually put into the 
compressor, and in this case represents 54.8% of tliat power or the adiabatic 
Horse Power of compression. 

As we are dealing with the "compressor end" in this article, it will be more 
pertinent to express the loss in terms of adiabatic compression which is done in 
table "B." 



Editor Compressed Air: 

I think it would be valued by your readers if you could give a diagram 
showing the temperature and volume which would result from compressing air, 
adiabatically, and in a single stage, to very high pressures, say 2,500 to 3,000 lbs. 
per square inch. Probably only an approximation could be given, but even that 
would be serviceable. Failing this, could you give a constant to enable same to 
be determined by calculation? 

Is there a point in air compression where the temperature reaches a maxi- 
mum above which continued compression cannot increase the sensible heat ? Sup- 
pose this were so and that we had compressed a quantity of air far beyond its 
(heat) saturation point. Assuming that we use this immediately in a motor, how 
will cooling take place ? Must the pressure fall to the heat saturation point again 
before the temperature begins to fall, or does temperature fall at once? 

If there is a heat saturation point, must there not also be a cold saturation 
point? Suppose that in using the above quantity of highly compressed air, we 
had first allowed it to fall to atmospheric temperature, would it continue to fall 
in temperature so long as expansion took place? 



122 PRODUCTION. 

In the compression of air temperature rises most during the early stages. 
How is it in expansion? Is it vice versa? T. T. 

Newcastle-on-Tyne, Eng. 

A diagram of adiabatic air compression, to be of any value, should be made 
on a larger scale than our space will allow, if carried up to 3,000 lbs. per square 
in. pressure. Compression to the higher figures is not practicable by one stage 
compression, for at 1,000 lbs. pressure the air rises to a full red heat, 13 13 degrees 
Fahr., and at 2,000 lbs. to 1709 degrees Fahr. 

This is the theoretical temperature, but as much of the heat in the air would 
be absorbed by the compressor, it would soon become too hot for economical 
operation. 

The formula for the temperature of compression is derived from the rela- 



tive absolute pressures and a ratio of adiabatic compression for gases. 



iW 



X (461.2+ /°)= r°Fah., in which p = the ultimate absolute pressure, i.e., the gauge 
pressure plus 14.7 and P =: the atmospheric pressure, 14.7. t= the initial tem- 
perature from zero Fahrenheit. — 461.2 is the temperature from absolute zero to 
the zero of the Fahrenheit scale. 

The ratio exponent, 0.29, is derived from the quotient of the division of the 
specific heat of air at constant pressure by the specific heat at constant volume. 

•2375 o -1 1.408— I 

-^^—1.408 and ^^ =0.2908 the ratio; practically the last figure is dropped 

and 0.29 used. The logarithm of the quotient of -^ must be used, when the oper- 
ation will then be for, say 100 lbs. gauge pressure from 60° initial temperature. 

^^^ = 7.803 log. 0.89225 
Multiplied by exponent, o. 29 
Index log. - - 0.2587525 

The index of which is 1.8145 X (46i°.2 + 60°) =94.S°.7i Fah. absolute tempera- 
ture; from which must be deducted 461^.2, leaving 484°.$ as the temperature of 
compression by the Fahrenheit scale. 

The limiting point of heat by the compression of air is unknown, but is 
probably at the pressure of liquefaction, which has not yet been found with pres- 
sures up to 15,000 lbs. per square inch. 

Cooling from the expansion of compressed air is inversely in the same ratio 
as for compression ; or, the temperature falls by the same scale that it rises. 

As we have said above, the heat saturation point is probably at the pressure 
of liquefaction ; so the cold extreme from expansion is probably at the absolutely 
zero of expansion or perfect vacuum; which is now accepted as the zero of ab- 
solute temperature 46i°.2 below the zero of the Fahrenheit scale. 



PRODUCTION. 123 



r 

^m The difference of temperature by compression for equal increments of pres- 

H sure, is much greater in the lower part of the compression scale than in the upper 
V part, as for example the increase of temperature from atmospheric pressure to 
« I lb. per square inch is 10 degrees Fah., while for an increase of i lb. pressure 
from 99 to 100 lbs. is but 2 4-10 degrees Fah. The differences of temperature 
when plotted on a pressure diagram form a parabolic curve from its axis at abso- 
lute zero and terminating at infinite pressure and temperature; the conditions 
within the limits of practice indicate this curve, as also its inverse order in the 
expansion of compressed air. 



AIR COMPRESSION AT HIGH ALTITUDES. 

The Reasons Which Cause Air Compressors to Give Less Efficiency at 

High Altitude. 

[Written for Mines and Minerals, by Robert Peele.] 

Because of the diminished density of the atmosphere at high altitudes, air 
compressors do not give the same results in mountainous regions as at sea level. 
Their effective capacity is reduced by reason of the smaller weight of air that is 
taken into the cylinder at each stroke. It is necessary, therefore, to make a de- 
duction from the normal output of a compressor of given size, working with air 
at ordinary atmospheric pressure. 

This matter is of special importance in connection with mining operations, 
because so many mines are at considerable elevations above sea level. The 
rated capacities of compressors, as given in the makers' catalogues, are for work 
at normal barometric pressure. This reduction in output is usually tabulated also 
in the catalogues, and must receive due consideration in order to avoid serious 
errors in ordering compressors. For example, the volume of compressed air 
delivered at 60 pounds pressure at an elevation of 10,000 feet is only 72.7 per cent, 
of the volume delivered at the same pressure by the same compressor at sea level. 
In other words, a compressor which, at sea level, will supply power for ten rock 
drills, will, at an elevation of 10,000 feet, furnish air for only seven drills. It 
should be observed that the heat of compression increases with the ratio of the 
final absolute pressure to initial absolute pressure. Therefore, as this ratio 
increases with the altitude, more heat will be generated by compression to a 
given pressure at high altitudes than at sea level, and there is a corresponding 
increased loss of work due to the subsequent cooling of the air. 

Contrary to a common impression, the volume of compressed air delivered 
by a given compressor is not proportional to the barometric pressure, nor is the 
power consumed in producing a given volume of air at a given pressure the same 
at all altitudes. As a matter of fact, the volume of air furnished by compressors 
of equal capacity, working at different heights above sea level, diminishes at a 
somewhat slower rate than the barometric pressure, but the power consumed in 



124 PRODUCTION. 

producing a given volume of compressed air increases with the altitude. Take 
one compressor working at normal barometric pressure, assumed for convenience 
to be 15 pounds, and another working under an atmospheric pressure of 10 
pounds, corresponding very nearly to an elevation of 10,000 feet. The first, if 
compressing to 6 atmospheres, will produce a gauge pressure of (15 X 6) — 15 = 
75 pounds. To produce the same gauge pressure the second compressor must 
work to an absolute pressure of 75 + 10 = 85 pounds. This, divided by the at- 
mospheric pressure of 10 pounds, gives 8.5 atmospheres required from the second 

6 
compressor. The ratio between the two, — = 0.706, shows the relative volumes 

8.5 
of compressed air produced under the assumed conditions. This is to be com- 
pared with the ratio between the corresponding barometric pressures, which is 
10 
— = 0.666. 

15 

The indicated horse power per cubic foot of piston displacement decreases 
.'is the altitude increases, but this decrease is not proportional to the altitude. To 
compensate for the increase of piston displacement per horse power, when com- 
pressing to a given gauge pressure at high altitudes, some builders make the air 
cylinders of compressors for mountain work of larger diameter than those at sea 
Itvel, for the same size of steam cylinder. 

It is sometimes argued that compressors whose inlet valves are under some 
mechanical control are of special advantage for work at high altitudes. While 
there is a measure of truth in this the possible saving which may be effected is 
necessarily small. The matter presents itself as follows • If the valve resistance 
be reduced by introducing mechanical control, so that, under normal conditions 
at sea level, the inlet air begins to enter the cylinder a little earlier in the stroke, 
the volumetric capacity of the compressor is increased. The loss due to resist- 
ance of the valve springs, etc., which may be taken as a constant at 0.75 pounds 
for ordinary poppet valves, becomes proportionally of greater and greater conse- 
quence as the altitude increases, because its ratio to the atmospheric pressure is 
increased. The percentage of saving obtained by eliminating the spring resist- 
ance, though small at sea level, therefore bears an increasmg ratio to the atmos- 
pheric pressure as the altitude increases. In other words, the inlet valve which 
presents the smallest resistance at normal atmospheric pressure will be the most 
economical valve as the atmospheric pressure decreases. 

According to the statement made above, the greater the altitude above sea 
level the smaller will be the ratio between the final pressure at delivery and the 
atmospheric pressure, that is, the ratio of compression. It is evident, therefore, 
that the percentage loss due to piston clearance increases with the altitude. It 
may be questioned whether it is worth while to adopt stage compression for the 
ordinary pressures used in mining and tunneling, but the case is materially 
altered at high altitudes. For example, if it be desired to produce a gauge 
pressure of 75 pounds at an altitude of 5,000 feet, 7.15 compressions are necessary. 
At sea level this ratio of compression would produce a gauge pressure of 105. i 
pounds. So far as the losses due to piston clearance are concerned, therefore, it 



PRODUCTION. 



125 



r 

H is as reasonable to employ stage compression for a gauge pressure of 75 pounds at 

H 5,000 feet elevation as for 105. i pounds at sea level. In a compound compressor, 

H too, it must be remembered that there is but one clearance space ; that in the low 

r pressure, or intake, cylinder. The value of the intercooler also increases with the 

altitude. — Mines and Minerals. 



TABLE 13. 
MULTIPLIERS TO BE USED FOR TRANSFORMING VOLUMES OF 
COMPRESSED AIR AT VARIOUS PRESSURES INTO CORRE- 
SPONDING VOLUMES OF FREE AIR AT ATMOSPHERIC PRES- 
SURE OF 147 POUNDS. 



OQ 




to 




ta 




OQ 




rn 




Q 




Q 




Q 




Q 




Q 




?5 




^ 




^ 




!Z5 




« 




p 





P 

2 


(A 
Eel 

M 


P 






PS 

s 


g 


1 


S 


§ 


[25 




M 


P4 


M 


s 


g 




m 


H 


w 


e^ 


a 


H 


H 


H 


a 


H 


« 


J 


ft* 




P^ 


»4 


Ph 


s 


PS 




P 


P 


h 




P 




P 


p 


p 






8 


OD 


S 


^ 


g 




s 


OQ 


S 


I 




g 




P? 




PS 




rt 




Ph 




P^ 




Ph 




Ph 




Ak 




1 


1.068027 


26 


2.768602 


51 


4.469377 


76 


6.170052 


101 


7.870727 


2 


1.136054 


27 


2.836729 


52 


4.537404 


77 


6.238079 


102 


7.938754 


8 


1.204081 


28 


2.904756 


53 


4.605431 


78 


6.306106 


103 


8.006781 


4 


1.272108 


29 


2.272783 


64 


4.673458 


79 


6.374133 


104 


8.074908 


5 


1.340135 


30 


3.040810 


65 


4.741485 


80 


6.442160 


105 


8.142835 


6 


1.408162 


31 


3.108837 


56 


4.809512 


81 


6.510187 


106 


8 210862 


7 


1.47618J) 


32 


3.176864 


57 


4.877539 


82 


6.578194 


107 


8.278889 


8 


1.544216 


33 


3.244891 


58 


4.945566 


83 


6.646241 


108 


8.346916 


9 


1.612243 


34 


3.312918 


59 


5.013593 


84 


6.714268 


109 


8.414943 


10 


1.680270 


35 


3.380945 


60 


5.081620 


85 


6.782295 


110 


8.482970 


11 


1.748297 


36 


3.448972 


61 


5.149647 


86 


6.850322 






18 


1.816324 


87 


3.516999 


62 


5.217674 


87 


6.918349 






13 


1.884351 


38 


3.585026 


63 


5.285701 


88 


6.986376 




« 


14 


1.952378 


39 


3.653053 


64 


5.353728 


89 


7.054403 




a, 


15 


2.020405 


40 


3.721080 


66 
66 


5.421755 


90 


7.122430 




9 


16 


2.088432 


41 


3.789107 


5.489782 


91 


7.190457 


S 


17 


2.156459 


42 


3.857134 


67 


5.557809 


92 


7.258484 




<sS ^ 


18 


2.224486 


43 


3.925161 


68 


5.625836 


93 


7.326511 




1 t 


19 


2.292513 


44 


3.993188 


69 


5.693863 


94 


7.394538 




20 


2.360540 


45 


4.061215 


70 


5.761890 


95 
96 


7.462565 
7.530592 




1 1 


21 


2.428567 


46 


4.129242 


71 


5.8291)17 


g 


22 


2.496594 


47 


4.197269 


72 


5.897944 


97 


7.599619 




Hh 


23 


2.564621 


48 


4.265296 


78 


5.965971 


98 


7.666646 




I— 


24 


2.632648 


49 


4.333323 


74 


6.033998 


99 


7.734673 




-^ '^. 


26 


2.700675 


50 


4.401350 


76 


6.102025 


100 


7.802700 




l-H 



126 PRODUCTION. 

Atmospheric Pressure 14.7 pounds = 30" Barometric Pressure Tempera- 
ture 60° Fahr. 

To find the volume of free air at atmospheric pressure corresponding to a 
volume of air under pressure, multiply the amount of air under pressure by the 
multiplier corresponding to that pressure. 

For each one-tenth of an inch difference in barometric pressure below 30 
inches, first reduce the volume of compressed air into volume of free air at 
atmospheric pressure of 30 inches or 14.7 pounds, according to the table. Then 
use the following formula: 

300-X 

in which V^ represents the volume of free air at reduced atmospheric pressure; 
V the volume of free air at atmospheric pressure of 14.7 pounds, and X the 
decrease in one-tenth of an inch barometric pressure below 30 inches. 

For each 5 degrees difference in temperature between end of pipe line and 
compressor, add or subtract, according to increased or decreased temperature, 
one per cent, to volume of free air. 

Examples : Assume that we have 320 cubic feet of air at 90 pounds pres- 
sure, the atmospheric pressure being 14.7 pounds and temperature 60 degrees, 
both at receiver and end of line. In looking over table of multipliers we find 
that the multiplier for 90 pounds is 7.12243. Thus the amount of free air would 
be 320 X 7.12243 = 2279 cubic feet of free air at 14.7 pounds. 

Suppose now that this would apply to Leadville, Colo., where the baro- 
metric pressure is 20.4 inches. The volume of free air at that pressure would 
then be as per formula above. 

300 

2279 X = 3351 cubic feet. 

300-96 ''^^ 

Assume now the temperature in receiver to be 60 degrees and that the air 

would be re-heated to 155 degrees, the volume of free air at 155 degrees and 20.4 

inches barometric pressure corresponding to above volume of compressed air 

would be 

3351 X (1+ — )=3987cubicfeetoffreeairat 155*^ and 20.4 in. barometric pressure 
\ 100/ 

in which 19 represents the increase of volume of one per cent, for each 5 degrees 
increase in temperature. 

The reverse can be done in order to determine the volume of compressed 
air at various pressures, when the volume of free air, barometric pressure, tem- 
perature of free air, temperature of compressed air and terminal pressure are 
known. This is effected by transforming the multipliers into dividers. Examples : 
What will be the amount of compressed air obtained from 4,000 cubic feet of free 
air at 60 degrees receiver temperature with initial barometric pressure of 20.4 
inches, initial temperature of 40 degrees and terminal pressure 90 pounds gauge ? 
We first reduce the volume to 30 inches barometric pressure, and have 

,. - . 300-X 300-06 

V= V 1 X ^ =4000 X ^=2720 

300 300 ^ 

cubic feet of free air at 14.7 pounds and 40 degrees. At 90 pounds and 40 degrees 



r 



. PRODUCTION. 



127 



we divide the amount by the multiplier corresponding for 90 pounds, and have 



2720 



:382 cubic feet. 



7.12243 

For an increase of temperature of 20 degrees we will have an increase of 
volume of one per cent, for each 5 degrees; thus the total amount would be 
382 X 1.04 = 397 cubic feet of compressed air at 90 pounds gauge pressure and 
60° temperature. F. Schmerber. 



REDUCING AIR FROM HIGH TO LOW PRESSURE. 

The use of compressed air, especially in cases where it is stored under a 
high pressure, has created a demand for a regulating valve that will reduce this 
high pressure to the normal working pressure desired in engines or elsewhere. 

The chief difficulty experienced in effecting a reduction from 1,000 lbs. or 
more, per square inch, to a working pressure of from 100 to 200 lbs., has been 




'*"''■ ij:-*''* 



FIG. 40. — MECHANICALLY OPERATED. 



found to lie in the fact that, with the maximum initial pressure in the reservoir, 
the reducing valve was opened to such a slight extent that the excessive wire- 
drawing, and the lodgment of fine particles of scale, cuttings, grit or other foreign 
substances which are always present under ordinary practical conditions, has 
resulted in so rapid a wearing of the seats and valves that the leakage quickly 
became serious, and the tight closing of the valve an impossibility. This diffi- 



128 



PRODUCTION. 



culty has been entirely obviated by the Foster combination regulator and aato- 
matic stop valve. 

The valve is made in two forms ; one operated mechanically, and the other 
pneumatically. In the mechanically operated valve (Fig. 40), the high pressure 
is admitted through the pipe 16, and when the valve in the body C is open, the full 
pressure of air flows in to the valves of the regulator in the case A, These valves 




FIG. 41. — PNEUMATICALLY OPERATED. 

are controlled by a diaphragm and the springs K, K, as in the standard "Class 
W" Foster regulator. Here it is reduced or wire-drawn down to the normal 
working pressure, and flows out through the pipe 17. So long as the throttle 
remains open, and there is a consumption of air, this state of things continues. 
When, however, the throttle is closed, the valve in the body C is also closed, and 
all flow - " irnm the supply pipe 16 to the regulator valve is cut off— a pipe 
being tapped in to the body C between the valve and source of supply. This pipe 
leads to the auxiliary valve B, which may be located in any convenient place in 
juxta-position to the engine throttle lever, and is always charged with high pres- 



PRODUCTION. 129 

sure air from the pipe 16. In B there are two small needle valves, one closing 
downward and held in that position by the combined pressure of a spring and the 
high pressure air. Abutting against this valve, and held open by it, is an upward 
closing valve which projects below the case at 2. When the engine throttle is 
closed, an adjustable screw in the lever thereof pushes this valve 2 shut and, in 
doing so, opens the one above it. The opening of this upper valve allows the 
high-pressure air to pass around through the pipe 3, and thence back to the joint 
5, and down the center of the spindle to the top of a piston within the casing 4. 
This piston rests on the same stem as the valve in the body C, and when air pres- 
sure is admitted to the top of the former, the latter is closed, thus shutting off the 
flow from the pipe 16. 

As soon as the throttle is opened, the pressure instantly closes the upper 
valve in B and, in so doing, opens the valve 2, which allows the air above the pis- 
ton in 4 to escape to the atmosphere. The valve in C is then opened by the pres- 
sure from the pipe 16 beneath it, and air is again admitted to the regulator valve A. 

The valve in body C can also be closed by means of the hand-wheel 6, after 
the manner of an ordinary stop valve. 

In the case of the pneumatically actuated valve (see Fig. 2) the high press- 
ure air is admitted at 16 and flows through the valve C to the regulator valve A, 
where the pressure is reduced as desired and whence it flows out at the delivery 
17. Tapped into the delivery pipe 17 is a small pipe leading down to the auxiliary 
valve B, where it enters beneath a diaphragm which is adjusted by a spring in 
the casing 5, so that the valve will open when the pressure in pipe 17 has risen a 
small amount above Jjje formal working pressure. When such a rise has taken 
place, this valve opens and air passes through the pipe 3 to the back of a dia- 
phragm working against a plate on the stem of the stop valve in C. The admis- 
sion of this pressure to the back of the diaphragm closes the valve C and cuts off 
the flow of air. As 'soon as the working pressure again falls to normal, the 
needle valves in casing B shuts off admission from pipe 17 and bleed the air from 
back of diaphragm in stop valve C to the atmosphere and allow this valve to 
instantly open. 

The result of this combination is that the valve in C is always either wide 
open or closed. There is, therefore, no wire-drawing at this point, and the ample 
opening of the valve permits any foreign substances that may be entrained by the 
air, to blow through. When the valve C is closed, that in A opens more than it 
does when in the normal working position, due to the fall of pressure that take^ 
place. Hence, at the instant of the opening of C, a puff of air is sent through A, 
cleaning the seats and preventing a lodgment of the grit. 

The cutting of the valve surfaces due to wire-drawing is obviated by the 
use of a hardened steel valve, which has been found to be efficient for the purpose. 



THE WEIGHT OF AIR. 



The properties of air and other gases are so different from the properties 
of the solid liquids that we ca'n see and measure and handle so readily, that it is 
not at all to be wondered at that the earlier men of science regarded gases as 



I30 PRODUCTION. 

intrinsically different, in their very essence, from the more familiar and tangible 
things of our daily experience. The word "gas" was invented by a Belgium 
chemist named Van Helmont, in the first half of the seventeenth century; and 
while it is not definitely known where he obtained the suggestion from which the 
word took form, it is not at all unlikely that it came from the Dutch word 
"geest," which means "a spirit," and which is related to our common English 
word "ghost." Whatever the origin of the word, it is certain that the early 
philosophers considered gases to be essentially different from the other materials 
of which the world is composed. We do not need to discuss the views that they 
held about these things, beyond stating that until the year 1644 it does not appear 
to have occurred to any one that gases (and, in particular, air) possess the prop- 
erty of weight. But in that year the Italian physicist Torricelli invented the 
barometer, and proved, by conclusive experiments, that air, at least, has weight, 
just as all the more substantial bodies have; and now, of course, we know that 
every mass of gas has a perfectly definite weight. 

It is not essential to our present purpose to describe, in detail, the experi- 
mental methods by which the air has been weighed. It will be sufficient to say 
that the general process consists in weighing a balloon-shaped flask twice — the 
first weighing being performed with the flask full of air, while the second is per- 
formed after the air has been all pumped out. If air had no weight at all, these 
two experiments would give identical results ; but it is found that, as a matter of 
fact, the flask is always sensibly heavier when it is full. By taking the differences 
of the two weighings, we therefore ascertain the weight of the quantity of air 
that is just sufficient to fill the flask. Knowing this, we next proceed, by means 
of a separate experiment, to find out the volume of the flask, in cubic inches ; and 
when this has been done, we are in position to calculate the weight of a cubic 
inch of air, or of a cubic foot of it, or of any other quantity. 

Measurements of this sort are exceedingly delicate, and they can be 
valuable only when performed by experienced men, with the aid of the finest 
apparatus that can be made. Regnault, whose skill cannot be doubted, and whose 
apparatus was beyond reproach, found that at the freezing point of water, a cubic 
centimeter of perfectly pure, dry air weighed 0.0012932 of a gramme, when the 
barometer stood at 76 centimeters, in his laboratory at Paris. To make this 
available for practical work in this country we have reduced these figures to their 
English equivalents ; and we find that at ordinary atmospheric pressure, and at 
the temperature of melting ice (32 degrees Fahr.), a cubic foot of air weighs 
0.080681 of a pound.* 



♦By "ordinary atmospheric pressure" we mean the pressure that would be exerted 
by a weight of 14.7 pounds, resting upon a base one inch square, at sea-level in the lati- 
tude of Washington ; and throughout this article when we use the word "pound" it is 
to be understood that the data relate always to sea-level, at Washington. We make this 
explanation in order to guard against possible criticism ; but for the purpose of engi- 
neering, no attention need be paid to this foot note, and the figures that we give may 
be used in any latitude, without fear of sensible error. The tables are supposed to be 
correct for Washington ; and if the force of gravity were constant all over the United 
States, they would be equally exact for all places in the country. As a matter of fact, 
the earth attracts bodies a little more strongly as we go north, and a little less strongly 



PRODUCTION. 



131 



It will be observed that we have carefully specified the pressure and tem- 
perature of the air, in giving weight. That is because the density of the air varies 
when these elements vary, unless certain conditions are fulfilled. If a given con- 
stant mass of air be compressed, or heated, or modified in any other way, its 
weight will remain unchanged, just as the weight of any other substance would 
remain unchanged under similar circumstances. The reason that the weight of a 
cubic foot of air varies so much under varying conditions of temperature and 
pressure is, that air is exceedingly expansible and compressible. Suppose, for 
example, that we had a light steel flask, with a capacity of precisely one cubic 
foot, and that we filled this box with air at the usual atmospheric pressure, and 
(say) at 70 degrees temperature. The air so confined would have a certain 
definite weight. Suppose, next, that we pump more air into the flask, until there 
is perhaps three times as much air in it as there was before. In pumping in this 
extra air, we shall materially increase the pressure within the flask ; but that does 
not concern us for the moment. The point that we wish to make is, that the air 



Hm iiitiniiiiiHiii 






Us 





-M 


. AIR 





-13. 


lliy^!^]! 


Zs. 

z 

—3 


ISil 


:■ AIR.,- 




— 





IZ 




-g 


ftsJI 


11 ^^3 


— 


||||§3 


Ze 


iJeIl 


— ' 




- 



kahtVoKd iitM* BtiklR INS* V mi 

FIG. 42. — ILLUSTRATING "bOYLE's LAW." 



that was originally in the flask weighs just exactly the same as it did before— no 
more and no less, but the total weight of the air in the flask is now greater than it 
was before, because we have forced a good deal more air into this one cubic foot 
of space than there was in it in the first place; and that is the reason (and the 
only reason) why a cubic foot of air at a higher pressure weighs more than a 
cubic foot of air at a lower pressure. There is simply more air crowded into this 
cubic foot, at the higher pressure. 

The first experimenter to investigate the behavior of air, under varying 
pressures, with anything like accuracy, was the English physicist, Robert Boyle, 
who discovered the fact of nature now known under the name of "Boyle's law." 
As this law is of constant use in connection with steam engineering and other 
allied branches, it will be worth our while to give some account of it. The law 



as we go south ; so that it is not possible to m&ke a table that shall be strictly accurate 
for all places. The greatest amount by which the tables can be in error from this cause, 
however, when they are applied to any part of the United States north or south of the 
latitude of Washington, Is only one-ninth of one per cent, this maximum error occur- 
ring at Key West. 



132 PRODUCTION. 

is very simple and will be readily understood by referring to the illustrations 
which accompany this article. On the left we have endeavored to represent a 
metal cylinder, standing on end, in which a definite mass of air confined by means 
of a weightless piston which fits the cylinder perfectly, and yet without the least 
friction. We cannot realize, in practice, the condition of an air-tight piston vs?^hich 
is at the same time perfectly frictionless ; but our limitations in this regard need 
not prevent us from imagining such a thing, nor from learning something about 
what the behavior of air would be, if such a state of affairs could be realized. 
For the sake of further simplicity, we will also suppose that the external air docs 
press down upon the piston at all, but that the only force tending to confine the air 
is that due to the lOO-pound weight which is represented in the engraving. This 
amounts to assuming that the whole experiment that we are about to describe is 
performed in a closed chamber, from which the air has been removed by a suit- 
able pump. In practice, such experiments are performed in the open air, and the 
effects of the external atmospheric pressure are allowed for in the calculations. 
We could pursue this latter course if we chose to, but as we are not going to 
actually perform the experiment, but only to think of its being performed, we 
might as well think of the external atmospheric pressure as being entirely done 
away with by some such means as we have suggested; for this will save all com- 
plication, and enable us to give our undivided attention to one thing that we wish 
to illustrate. 

We have, then, a metal cylinder in which a certain definite amount of air is 
confined by means of a tight-fitting but frictionless piston ; and the only force 
tending to hold this air confined is that exerted by the lOO-pound weight which 
rests upon the piston. We will suppose that the quantity of air within the cylin- 
der has been regulated so nicely that the weight is held by it at such a height that 
the bottom of the piston is precisely 12 inches from the bottom of the cylinder. 
If there is no leakage past the piston, and no change in the temperature of the air, 
the system will remain balanced in this precise condition forever (so far as we 
know). 

Now, suppose that another loo-pound weight is placed upon the piston. 
The piston will be immediately forced downward by the additional weight, and 
the air under it will be compressed, and the pressure that the air exerts against 
each square inch of the cylinder and the piston will be greater than it was before. 
There will be various effects produced at the outset, besides the mere reduction of 
the air to a smaller volume. For example, small currents will be set up in the air, 
and the air will also become more or less heated. If we wait, however, until all 
these currents have died out, and the air has cooled again to its original tempera- 
ture, we shall find that the piston comes finally to rest at a position such that its 
lower side is almost precisely six inches from the bottom of the cylinder, instead 
of twelve, as it was originally. That is, by doubling the pressure upon the air we 
have reduced the volume of the air to one-half of what it was at first— always 
understanding that the temperature of the air is precisely the same in both cases. 
If we had loaded the piston with three hundred pounds, we should have found that 
when the system finally came to rest, the volume of the enclosed air would be 
one-third of its original volume. If we piled 400 pounds on the piston, we should 
find that the volume would be reduced to one-fourth of its original value, as 



i il 

p. 



PRODUCTION. 133 

shown on the extreme right of the engraving; and so on, for all ordinary pres- 
sures. This fact, that the volume of air (or of any other of the so-called "per- 
manent gases") is halved by doubling the pressure, and so on (provided the 
temperature of the air remains constant), is known as "Boyle's law." 

It will be plain, upon examining the engraving, why the weight of a cubic 
foot (or of a cubic inch) of air varies with the pressure; for under a load (or 
pressure) of 400 pounds, the same air is forced into a space only one-fourth as 
great as it occupied under a load of 100 pounds; and therefore its density (or, in 
other words, its weight per cubic foot, or per cubic inch), is four times as great 
at the higher pressure. 

We have referred, several times, to the necessity of keeping the temperature 
of the air constant during experiments of this kind, if "Boyle's law" is to be 
illustrated. We shall now explain briefly what happens when the temperature of 
the air is not kept constant; and we shall find that the effects of change of tem- 
perature are almost equally as simple as the effects of change of pressure. In the 
interest of simplicity it will be well to state, at the outset, that physicists are in 
the habit of reckoning temperatures, not from the arbitrary zero of the Fahrenheit 
scale, but from a point which is approximately 460° Fahrenheit below this zero. 
The scientific starting point, or zero, so determined, is called the "absolute zero," 
because it is believed to be the temperature at which all bodies are totally destitute 
of heat; and temperatures reckoned from this "absolute zero" are called "abso- 
lute temperatures." To illustrate : The freezing point of water, on the ordinary 
Fahrenheit scale, is at 32° ; and the "absolute temperature" of this point will 
therefore be 460° + 32° or 492°. Again, the boiling point of water, under one 
atmospheric pressure, is 212° on the ordinary Fahrenheit scale ; and therefore the 
"absolute temperature" of this point is 460° + 212° or 672°. 

With this much understood, we are now prepared to state what is known 
as "Gay Lussac's law" (or, "Charles' law") ; which is, that if the pressure exerted 
upon a given mass of air (or any other "permanent gas") be kept constant, the 
volume of the air (or gas) will vary proportionately to the "absolute tempera- 
ture" of the gas. For example, consider the second of the engravings accom- 
panying this article, where the air is confined by a total weight of 200 pounds. 
Let us suppose that this air, at the outset, is at the freezing point, or at 32° on 
the ordinary Fahrenheit scale; and let us imagine the air to heated, in some way, 
until its temperature becomes 524° on this same scale, the load of 200 pounds 
being kept constant all the while. To find out how much the air will expand 
under these circumstances, we first convert the ordinary temperatures, given 
above, in "absolute temperature," by adding 460° to each of them. We have 460" 
plus 32° or 492°, and 460° plus 524° or 984°. Now "Gay Lussac's law" states that 
so long as we keep the pressure constant, the volume will increase proportionately 
to the "absolute temperature;" and since 984 is just twice as great as 492, it 
follows that the air will expand, under the stated conditions, until its volume is 
precisely double what it was at the beginning. That is, the mass of air shown in 
the second illustration will push up the load of 200 pounds until the piston comes 
into the position shown in the first of these illustrations. 

By means of the laws of Boyle and Gay Lussac, we can calculate the way in 
which the volume of a given mass of air will vary under any imaginable circum- 



134 PRODUCTION. 

stances of pressure and temperature, and hence we can calculate how much a 
cubic foot of air will weigh at any proposed temperature and pressure, when we 
once know, by experiment, how much such a volume of air will weigh under 
certain definite standard conditions— say at one atmosphere pressure, and at the 
temperature of freezing water. Regnault's labors, referred to earlier in this 
article, showed that a cubic foot of air exposed to a pressure of 147 pounds per 
square inch and a temperature of 32° Fahr., weighs .080681 of a pound (or 1.29 
ounces) . 

The atmosphere that surrounds us buoys up everything that is submerged 
in it, just as water does, only not to so great an extent. If a cannon ball is sub- 
merged in water, the water buoys it up by an amount which is precisely equal to 
the weight of a mass of water having identically the same size and shape as the 
cannon ball itself; and when the cannon ball is submerged in air, instead of in 
water, the surrounding air buoys up the ball by an amount which is precisely 
equal to the absolute weight of a mass of air having the identical size and shape 
of the cannon ball ; and so on with any other fluid or gas, whether it is water or 
milk or carbonic acid gas or coal gas or anything else. — The Locomotive. 



AIR COMPRESSORS. 



The widening use of compressed air in the arts has developed a great many 
types of Air Compressors and has distinctly improved the efficiency of the 
machine. A few years ago it was an uncommon thing for an Air Compressor 
builder to supply a machine with compound air cylinders; to-day the best Com- 
pressors are of the compound type and an engineer who specifies an Air Com- 
pressor for his plant, is wise if he looks carefully into the tender submitted, 
especially with reference to compounding and intercooling. It is quite as impor- 
tant in large plants that the air cylinders be compounded, as that compound 
steam cylinders are used, and it is equally as important to supply efficient inter- 
coolers as to use a condenser on the steam end. 

There is, naturally, at the present time, but little general familiarity with 
Air Compressors and compressed air machinery; hence, when those in charge of 
works decide to install a Compressor, they are at a loss to know how to draw up 
the specifications or to decide which of the numerous types is preferable. The 
plan which might be called European, and which applies to machinery and con- 
structive work generally, is to send out specifications and ask for bids. This is a 
dangerous thing to do unless the person who draws the specificatoins is thor- 
oughly familiar with the eubject. Such familiarity is not likely to exist in places 
where Air Compressors are required; hence, it is of greater importance to inves- 
tigate the question as to the experience and standing of the bidder. — How long 
has a certain concern been building Air Compressors ? What shop facilities they 
have for turning out the work, and what is the general design of their machine. 
A first-class builder of large experience and a growing business might naturally 
be expected to supply something of a high class in this line, and yet it may be 
found, on investigation, that this builder has a specialty that his machines are 



PRODUCTION. 135 

mainly used for light duty or low pressure, or vice-versa. References and testi- 
monials are easily given and are only of value in connection with a case of this 
kind in so far as they point to the class of trade which the manufacturer has been 
supplying, and if the buyer is not in too much of a hurry, he will do well to inves- 
tigate the references. In connection with this subject, the following specifica- 
tions have been brought to our notice as having been submitted to builders of Air 
Compressors, by two of the largest concerns in the country. They may be of 
interest to our readers as indicating types of specifications which are sent out 
when calling for bids: 

"Dimensions of steam and air cylinders to be determined by maker ; to be of 
sufficient size for compressing 650 cubic feet of free air per minute, to 750 pounds 
per square inch in three stages, at a maximum piston speed of 400 feet per minute. 
Initial pressure of steam 80 pounds, taken from a steam line 175 feet in length, 
from boiler to compressors. The whole machine to be designed to withstand 
1250 lbs. pressure in third compressing cylinder. 

"Builder to furnish complete plans and detail specifications, templates, foun- 
dation bolts, oil cups, sight feed lubricator, exhaust pipe, wrenches, and all fittings 
to make compressor complete for making trial test; also to furnish, at builder's 
expense, a competent machinist to superintend the erection of compressor, the 
buyer to furnish all unskilled labor and prepare the foundations for receiving 
compressor." 

"Capacity. — Capacity of compressor 600 to 650 cubic feet of free air per 
minute, compressed to 100 pounds per square inch, with 100 pounds per square 
inch steam pressure. 

"Specifications. — Signed specifications to be furnished covering work- 
manship, guarantee in regard to same, details of various parts, tools with com- 
pressor, time of delivery after ordered, etc. 

"Pi<ANS. — Foundation plans and print showing plan of compressor giving 
general dimensions, location of pipes, etc. Also photograph or catalogues and page 
number where compressor is shown to be furnished. 

General Information to Be Given. 

"Type of compressor. 

"Diameter of steam and air cylinders with stroke. 

"Free air capacity per minute. 

"Piston speed. 

"Revolutions. 

"Sizes of pipes. 

"Floor space. 

"Price. 

"Point of delivery." 

These specifications are conspicuous for their simplicity in that they throw 
the entire responsibility upon the maker. It is evident that if a maker is called 
upon to build something not strictly in line with his practice, or which is based 
upon the design of some other maker, he is not likely to do the subject justice 
and the buyer will run some risk in placing the order with him, because it will 
be more or less experimental. Air Compressors can only be built well when based 



136 PRODUCTION. 

on experience. The best design made by the best men will fail unless tested and 
developed on lines of practice. 

Compressed air, to the average mind, conveys a rather vague meaning, 
which ranges from the old-fashioned pop-gun to liquefied air. That it is produced 
by some form of pump is generally understood, but what the pump is, how it 
works and the principles governing its best action are unthought of points by the 
layman. The expert, on the other hand, knows the principles involved, and is 
constantly on the lookout for improvements in details of apparatus. From this 
standpoint, it is interesting to examine the air compressors exhibited at the 
Paris Exposition. 

In the first place, the number of such compressors is limited, there being, 
so far as is known to the writer, three compressors in operation on the Champ- 
de-Mars and three at Vincennes, and several other stationary ones. Of these 
former, five are American machines. Of course, Paris is an extensive user of 
compressed air, and its pneumatic street railways, clock and postal systems are 
unique ; but this apparatus does not form part of the Exposition, and it is, there- 
fore, outside of the purpose of this paper to discuss this. 

Generally speaking, compressors of all manufactures are horizontal, and 
the wisdom of having air cylinders behind and in direct line with the steam 
cylinders seems to have made this form standard practice, as it has certainly 
been adopted by the important manufacturers on both sides of the water. 

The engine may be termed girder framed, either cross, duplex or com- 
pound, depending upon initial steam pressure, which, in the United States, 
averages close upon lOO, while on the Continent, it is nearer 75 pounds. Slow 
speed engines, with a fairly long stroke, are used, the American builders favor- 
ing a much longer stroke than the Continental, at least, in the larger sizes. 

Cranks are set at 90 degrees, thus balancing better and distributing the 
load over the entire stroke. With one or two exceptions, heavy flywheels are 
universal, the necessity of carrying the cranks past dead points being very im- 
portant and fully understood. One maker, however, has an extremely light 
wheel, the wisdom of which may be seriously questioned. 

Regarding steam valve mechanism, Continental manufacturers lean 
towards slide valves of the Meyer's type, even in the larger sizes of engines, al- 
though poppet and modified Corliss valves are also used in the larger sizes. 
Manufacturers in the United States prefer the Corliss valve, excepting smaller 
sizes or those forms intended for places such as coal mines, where steam economy 
is a minor item. 

In a general way, the engines may be termed average, conforming to usual 
Continental engine practice, certainly no better, and, perhaps, not so good as 
American practice for the same dass of work. 

Coming to the air-compressing portion, such as the cylinder valves, etc., 
some interesting departures, or, perhaps, we may say, antiquities, arc noticeable. 
The larger sizes follow the usual practice of placing the air cylinder on a 
separate portion of the foundation and holding it at its proper distance by means 
of bolts or distance piecesw In the case of the smaller sizes, some manufac- 
turers mount all working parts on one base, but the self-contained type, familiar 



PRODUCTION. , 137 

in the United States, is not generally to be observed, and when used, it is a 
clumsy, awkward appearing affair. 

It is when the valves and cooling methods are examined that the chief 
difference is found. With few exceptions. Continental practice leans towards 
slide valves, the "Weiss" system. This is nothing more or less than a balanced 
plate slide valve. No particular effort seems to be made to reduce clearance in 
this type. 

In low pressure work for blowers, poppet valves in the heads are, how- 
ever, used to some extent. But it is safe to say that on the Continent air com- 
pressors for pressures of from 3 to 7 kilos, or even higher, slide valves are the 
rule. In the United States, with few exceptions, slide valves for air cylinders 
have been abandoned entirely by progressive manufacturers. 

It is interesting to note that Continental steam engine practice employs 
balanced poppet valves, and for their compressors slide valves. In the States, on 
the contrary, engines are equipped with slide and Corliss valves, and compressors 
with poppet valves. 

Attention must be called to one type of compressor which is somewhat 
common. This form resembles a duplex or cross compound engine, the en- 
gine portion forming one side and the compressor the other. This type requires 
heavy cranks, shaft and flywheel, and cannot be as satisfactory as other types, 
although it is a common type. 

Methods of cooling differ. The old injection system of spraying water 
into the cylinder with the inlet air still finds favor and is employed to some ex- 
tent. Cylinders are in other cases jacketed fairly well, but the valve of the slide 
valve types cannot of necessity be cooled, and, in addition, the entering air is in 
very close contact with the outgoing compressed and hot air. 

Compound compression is rather rare, at least for average pressures, and 
consequently no attempt is made at inter-cooling, which, in the United States, is 
considered an important feature. After cooling, or a consistent effort to remove 
moisture after compression, is not considered necessary, largely because low 
pressures are used and transmission to any considerable distance is seldom 
attempted. 

Contrasted from the standpoint of general appearance, that is, neatness of 
design, it must be admitted that the American machines have a solid, compact 
and business-like look which is most pleasing to the practical eye. When it 
comes to "finish," using the term to mean paint, varnish and nickel plating, it 
must be admitted that generally the Continental apparatus makes the best show- 
ing. Inspection, however, shows splendid work and materials on the essential 
parts of the American machines, with an accuracy which leaves little to be de- 
sired. — ^J. J. S., in London Engineering Times. 



INTER-COOLERS. 



Builders of air compressors and those who use compressed air will agree 
that the problem of heating or cooling air is a difficult one. Hot air in the 
cylinder of an air compressor means a reduction in the efficiency of the machine. 



138 ^ PRODUCTION. 

The trouble is, that there is not sufficient time during the stroke to cool thor- 
oughly by any available means. Water jacketing is the generally accepted prac- 
tice, but it does not by any means effect thorough cooling. The air in the cylinder 
is so large in volume that but a fraction of its surface is brought in contact with 
the jacketed parts. Air is a bad conductor of heat and takes time to change its 
temperature. The piston while pushing the air towards the heat rapidly drives 
it away from the jacketed surfaces; so that little or no cooling takes place. This 
is especially true of large cylinders where the economy effected by water jackets 
is considerably less than for small cylinders. Engineers who are shown indicator 
cards from large air compressors with pressure lines running away from the 
adiabatic, naturally regard them with suspicion and look for leaks past the piston 
or through the valves. Such leaks will explain many isothermal cards, and until 
something better than a water jacket is devised, it is well to seek economy in air 
compression through compounding. The great advantage of compounding is in 
the fact that more time is taken to compress a certain volume of air and that this 
air while being compressed is brought in contact with a larger percentage of 
jacketed surfaces. The inter-cooler which should always be used with com- 
pound machines effects a larger saving by cooling and thereby causing the air 
to shrink in volume between the stages. The trouble with inter-coolers is that 
manufacturers are too prone to build them of cheap construction, economizing in 
machinery and in space and losing in thermic efficiency. A properly designed inter- 
cooler should reduce the temperature of the air back to the original point, that is 
to the temperature of the intake air. It can even do more than this, especially in 
winter when the water used in the inter-cooler is of low temperature. A simple coil 
of pipe submerged in water is not an effective inter-cooler, because the air passes 
through the coil too rapidly to be cooled to the core, and such inter-coolers do 
not sufficiently split up the air to enable it to be cooled rapidly. This splitting 
up of the air is an important point. It will not do to depend upon baffle plates, 
coils and other water jacketed features unless the air is split up while being 
brought in contact with them. A theoretically perfect inter-cooler is one in which 
the entire volume of air after partial compression is made to pass through wire 
cloth of close mesh, each wire being a tube through which water is passed, no 
such device is in use, as the mechanical difficulties probably stand in the way, 
but it is well for engineers in drawing up specifications for air compressors to pay 
close attention to the inter-cooler and in fact to all jacketed surfaces. A nest of 
tubes carrying water and arranged so that the air is forced between and around 
the tubes is an efficient form of inter-cooler. If the tubes are close enough 
together and are kept cold, the air must split up into thin sheets while passing 
through. Such devices are naturally expensive, but the first cost is a small 
expense when compared with the efficiency of the compressor, measured in the 
coal and water consumed. 

Receiver inter-coolers are more efficient than those of the common type 
because the air is given more time to pass through the cooling stages and because 
of the freedom from wire drawing which may take place in inter-coolers of 
small volumetric capacity. This wire drawing is similar in effect to insufficient 
area of inlet and may be noticed by putting a pressure gauge on the inter-cooler. 



PRODUCTION. 139 

After-coolers are in some installations as important as inter-coolers. An 
after-cooler serves to reduce the temperature of the air after the final compres- 
sion. In doing this it serves as a drier, reducing the temperature of the air to 
the dew point, thus abstracting moisture before the air is started on its journey. 
In cold weather with air pipes laid over the ground an after-cooler may prevent 
accumulation of frost in the interior walls of the pipes, for where the hot com- 
pressed air is allowed to cool gradually the walls of the pipe in cold weather act 
like a surface condenser and moisture may be deposited on the inside for the 
same reason that we have frost on the inner side of a window pane. Another 
advantage of the after-cooler is that it keeps the temperature of the line pipe 
uniform, otherwise this pipe will be hottest near the compressor, gradually cool- 
ing down and being thus subject to irregularities of expansion and contraction. 



Editor Compressed Air: 

In a certain experience with Air Compressors the question arose as to the 
quantity of water used by the water jackets on simple machines, and in the in- 
tercooler on compound machines, for example, take a simple machine 14" by 18", 
and a compound machine 10" by 12". 

Take the temperature of water to be used at 60°, can you say how much 
water will be used by the water jacket on the simple machine, and how much 
will be used in the water jackets and intercooler combined on the compound 
machine? In the case mentioned the cost of water is, say, 8 cents per 1,000 
gallons, and used only to operate the compressors. 

All water in excess of that used in the boiler was thrown away. 

Figuring coal at $2.00 per ton and a boiler that will evaporate about 6 
pounds of water to each pound of coal, I would like to have your estimate as to 
the cost of operating each machine. Yours, 
Chicago. Engineer. 



The question presented here is best solved by the use of a mathematical 
formula. However, as the average reader of this column might get a better 
understanding without the use of symbols, we will try to present the matter as 
clearly as we know how without them. 

The amount of heat taken up by a pound of water has been determined 
experimentally a number of times, and is a matter of common knowledge to the 
engineer. 

The increase in temperature in compressing air is also known, for every 
terminal pressure or it can be easily taken with a thermometer. 

Having given both the temperatures of air, before and after compression, 
also the temperature of entering and exit jacket water, we can obtain the pounds 
of water required for every pound of air (say 13 cu. ft. free air) by dividing 
the rise in air temperature by the rise in water temperature and multiplying this 
quotient by 0.2375. 



140 PRODUCTION. 

There is considerable radiation going on, however, from unjacketed cyl- 
inder heads, and the above product can safely be divided by 2 or 3 to give the 
weight of water necessary for assumed conditions of temperature. 

It is common practice to use the jacket water as feed water for the boilers. 

The following is from a recent test observation: 

Temp, of air at inlet 78° 

Temp, of air at discharge 356"* 

Rise in Temp, of air 278'* 

Temp, of entering jacket water 46** 

Temp, of leaving jacket water 94° 

Rise in Temp 48° 

278 

= 5-8 5.8X.2375 = 1.37 

48 

1-37 

=.68 per pound of air. 

2 

Actual as found by test, .31 per pound of air. This is due to very large 
radiating surface in the plant tested and indicates that 3 or 4 would be a better 
divisor in that case. 

If much water is used Its temperature will be but little increased in passing 
through the jacket, and if little water is used the temperature may rise 30° or 
40° in the water, but as this would still be much colder than the air, it would 
still play an important part in cooling the air. We give below a few actual 
conditions : 

An 18" X 24" compressor (air pressure 80 pounds) used one pound of 
water per minute for every 14 cu. ft. of free air, and increased the temperature 
of water from 53° to 73°, so here it would have been better to use more water, 
say about a pound for 8 or 10 cu. ft. free air. 

On a compound machine the quantity used was one pound of water per 
minute for 8 cu. ft. of free air, and increased temperature of water from 56° to 
83°, or where more water was used, that is, one pound per minute to 2^ cu. ft. 
of free air, the temperature would be increased from 56° to 66°.— Ed.] 



THE SPEED OF AIR COMPRESSORS. 



BY FRANK RICHARDS. 



The following letter has been handed to me: 

"I have never seen in the American Machinist any discussion as to the 
proper speed of an air compressor. What speeds are and what are not practica- 
ble? It is obvious to those who have looked into the matter that the speeds of 
air compressors are commonly low, but whether this is imperative, or whether 
it is only that present practice has not yet reached the permissible speeds, is the 
question, and if much higher speeds may yet be employed, what are the present 



rvB--.^- 



PRODUCTION. 141 

hindrances and what the most promising means for overcoming them? These 
things seem to me to offer a very good field for useful statement and discussion, 
and I should be much interested, and I believe many others would be, if the 
subject were taken up in your columns. A Subscriber." 

The ultimate speed of an air compressor, like that of a steam engine, is 
the result of a compromise. It is of course desirable that any machine shall 
accomplish as much as possible, and the inevitable impulse is to speed it up. 
There is, however, always reached a limit beyond which the speeding up ceases 
to be profitable. None can be more interested in developing the highest efficiency 
in any class of machinery than the builders of such machinery, for those who can 
show the highest efficiency have the best of the argument with the customer. In 
their search for the higher efficiencies the builders also, if in healthy communica- 
tion with the users of their machinery, have the best opportunities for learning the 
conditions, including in this case that of piston speed, which limit and determine 
the capacity. When the builders publish tables of data concerning their air com- 
pressors of different sizes and styles, including piston speeds and volumes of air 
compressed, we may assume that they speak from the most reliable knowledge, 
and that they are at the same time disposed to make as good a showing as 
possible, I have before me^the catalogue of one of the largest and most successful 
builders of air compressors, in which are given the piston speeds of a large num- 
ber of their machines. These speeds range from 150 feet to 620 feet per minute, 
the former being for little machines of only 6-inch stroke, and the latter for the 
largest Corliss engine compressors of 5-foot stroke. 

Now, it is rather a matter of taste as to what we shall call fast and what we 
shall call slow. Our correspondent above would call these speeds slow, while I 
would not. Steam-driven air compressors usually have no governors or speed 
regulators, so that they may be speeded up by simply turning the throttle wheel, 
but not. with all-around satisfaction. A large increase of speed will usually give 
but a small increase of delivery, and the valves and working parts of the machines 
suffer rapid wear or frequent breakage. Air compressors are often installed for 
a single job, as for operating rock-drills where a long tunnel is to be driven or a 
deep shaft sunk, and here little care is given to the compressor if it will but 
stand by the job to completion, and damage to it is little thought of if large 
volumes of air can be delivered, and in such service the speed limits of air com- 
pressors have been thoroughly, if not closely ascertained. 

The objections to high speed for an air compressor begin, right at the be- 
ginning, with the operation of getting the air into the cylinder. During the intake 
stroke, as the piston recedes the air is, of course, driven into the cylinder by the 
pressure of the external atmosphere. To cause the air to flow in there must 
always be a difference of pressure between the inside and outside of the cylinder, 
and the pressure outside can be nothing more than the normal atmospheric pres- 
sure, so that the pressure within the cylinder on the intake stroke must always be 
something less than this. To increase the velocity at which the air must flow in, 
and especially to start the flowing of the column of air more frequently, as must 
be done when the speed is increased, demands a greater difference between the 
internal and the external pressures, or a reduced pressure within the cylinder, 



142 PRODUCTION. 

and this must mean that a less weight of air will constitute a cylinderful, and less 
air will be compressed and delivered per stroke. 

An additional loss is entailed by an increase of speed in the case of the 
two-stage compressor, as it must necessarily affect, and always disadvantageously, 
the efficiency of the intercooler. The intercooler is the only justification of the 
two-stage, compressor, and a two-stage air compressor without an efficient inter- 
cooler is a mechanical absurdity. Power is saved by cooling the air after it is par- 
tially compressed and so reducing the volume to be operated upon in the second 
cylinder. The best intercooler at its best is not too efficient, and as when the 
speed of the compressor is increased the heated air must pass through it more 
frequently and more rapidly, it cannot be as completely cooled. 

An increase in the speed of the air compressor means also increased dif- 
ficulty in properly lubricating the cylinder. With an inital temperature of 60 de- 
grees Fahrenheit, the final temperature of the air in the cylinder of a single-stage 
air compressor when delivering air at, say, six atmospheres is above 400 degrees, 
while in the first cylinder of a two-stage compressor it is nearly 300 degrees, so 
that the difficulty of maintaining proper lubrication may easily be appreciated. 
The water jacket may not count for much in its effect upon the air within the 
cylinder during the compression stroke, but it is of great service in keeping the 
inner surface of the cylinder at least cool enough to prevent the actual burning of 
the oil. This service is quite seriously impaired if the piston speeds are much in- 
creased. The failure of the lubricant, and the burning and cutting of the cylinder 
and valve surfaces are familiar and costly experiences accompanying the reckless 
speeding up of compressors. 

There is positive danger in running a compressor at such a speed that the 
air cooling devices employed do not have sufficient time to do their work com- 
pletely. Serious explosions have been caused by the ignition of mixtures of oil 
vapor and air in the cylinders or other parts. One such accident occurred within 
my knowledge quite recently, in which the intercooler between the cylinders of a 
compound compressor was blown to pieces, and an important service was inter- 
rupted for a long time in consequence. In some cases men have been killed by 
similar accidents. 

And then there is the trouble with the pounding of the valves. The main- 
tenance of the valves of the compressor is usually the largest item of repairs. 
They are usually poppet valves, and the elasticity of the air causes them to move 
in both directions at a lively gait and to strike hard, and of course this is much 
worse at high speeds. There may yet be devised valves with sliding movements 
that will avoid some of the most objectionable features of the poppet valves, and, 
so far as they are concerned, make somewhat higher speeds permissible, but they 
will be more than likely to bring other troubles in their train as great as those 
which they attempt to cure, and especially in the difficulty of proper lubrication. 

Thus there are several particulars to be suggested which tend to limit the 
profitable speed of the air compressor. They are none of them of a character to 
be handled with figures and formulas, but experience speaks with sufficient clear- 
ness and sharpness in the matter. It is not probable that much higher speeds 



PRODUCTION. 143 

will be established for air compressors than those now prevailing. The limit will, 
of course, be where it does not pay, all things considered to run any faster. — 
American Machinist. 



215 Heath St., 
Roxbury, Mass., May 29, 1899. 
Editor Compressed Air: 

Being a reader of your paper, and being interested in Carbonic Acid Gas 
Compressors, I would like to ask you if you know of any lubricant for use on 
swch Carbonic Acid Gas Cylinders that no trouble will occur from the gas being 
impregnated with foreign odors. What would you advise as a lubricant for 
same? This is for a compressor for 1,200 lbs. pressure. Also what would be the 
best arrangement for stuffing boxes to prevent leakage ? Yours very truly, 

J. J. FINLAY. 

Glycerine is used where perfect freedom from odor is required. Cotton- 
seed oil has been used, and if applied sparingly in the stuffing boxes and cylinders 
is almost odorless. For packing the piston rod of a double-acting carbonic acid 
gas pump, any of the mixed fibre and rubber packings; the "Garlock" or "Selden" 
are good. For a plunger pump, cupped leather rings should be used. 



COMPOUNDING AIR COMPRESSOR CYLINDER. 

" The air end of a compressor appears at present to be going through the 
stages followed by the steam engine during the early history of its development. 
Low pressures and plain slide valves in the steam engine have given place to 
higher pressures, compounding and Corliss and other forms of cut off valves. 
But a few years ago there was but one manufacturer of air compressors in 
America who built compound machines and who applied positive or mechanically 
moved valves to the air cylinders. This condition, of course, was largely due to 
the fact that compressed air was looked upon as a luxury which could only be 
produced at a sacrifice, and which could only be used in work like caisson sinking, 
tunnel driving and mining. It is true that there were a few other limited applica- 
tions of compressed air, but the quantities of air used was so small, that little in- 
terest was taken in the item of cost of production. The pace set by electricity, 
even in mining, and the growing use of compressed air in shops, about railroads 
and other industrial enterprises brought the question of cost of production to the 
attention of builders in such a way that it became an important condition in com- 
petition to produce air power at low cost, and it has been found that there has 
been more gained through compounding than through anything else. 

The following table will serve to illustrate the large saving that it is pos- 
sible to effect by compounding. This table gives the percentage of work lost by 
the heat of compression, taking isothermal compression or compression without 
heat as a base : 



144 



PRODUCTION. 

TABLE 14. 





One Stage. . 


Two Stage. 


Four Stage. 


Gauge 








Pressures. 


N = 1.408 






60 


30.00 c/ 


13.38 % 


4.65 % 


80 


84.00 " 


15.12 " 


5.04 " 


100 


38.00 " 


17.10 " 


8.00 " 


200 


52.35 " 


23.20 " 


9.01 " 


400 


68.60 " 


29.70 " 


12.40 " 


600 


83.75 " 


32.65 " 


15.06 " 


800 


90.00 " 


^5.80 " 


16.74 *' 


1000 


96.80 " 


39.00 " 


16.90 " 


1200 


106.15 " 


40.00 " 


17.45 " 


1400 


108.00 " 


41.60 '' 


17.70 " 


1600 


110.00 " 


42.90 " 


18.40 " 


1800 


116.80 " 


44.40 " 


19.12 '* 


2000 


121.70 " 


44.60 " 


20.00 " 



In columns 2, 3 and 4 no account is taken o£ jacket cooling, it being a well 
known fact among pneumatic engineers that water jackets, especially cylinder 
jackets, though useful and perhaps indispensable are not efficient in cooling es- 
pecially so in large compressors. The volume of air is so great in proportion to 
the surface exposed and the time of compression so short, that little or no cooling 
takes place. Jacketed heads are useful auxiliaries in cooling, but it has become an 
accepted theory among engineers that compounding or stage compression is more 
fertile as a means of economy than any other system that has yet been devised. 
The two and four stage figures in this table (columns 3 and 4), are based on re- 
duction to atmospheric temperature 60° Fahrenheit between stages. This is an 
important condition and in order to effect It much depends on the intercooler. In 
this device we have a case of jacket cooling which in practice has been found to 
be efficient where engineers specify intercoolers of proper design. While cooling 
between stages we may split the air up into thin layers and thus cool it efficiently 
in a short time, a condition not possible during compression. This splitting up 
process should be done thoroughly, and while it adds to the cost of the plant to 
provide efficient coolers, it pays in the end. A rule which might be observed to 
advantage among engineers is to specify that the manufacturer should supply a 
compressor with coolers provided with one square foot of tube cooling surface for 
every ten cubic feet of free air furnished by the compressor when running at its 
normal speed. 

Referring again to the table, we learn that when air is compressed to 100 
lbs. pressure per square inch in a single stage compressor without cooling, the heat 
loss may be thirty-eight per cent. (38%). This condition of course, does not 
exist in practice, except perhaps, at exceedingly high speeds, as there will be some 
absorption of heat by the exposed parts of the machine. It is safe however to say 
that in large air compressors that compress in a single stage up to 100 lbs. guage 
pressure, the heat loss is thirty per cent. (30%). This as shown in the table may 
be cut down more than one-half by compounding or compressing in two stages, 



PRODUCTION. 



145 



and with three stages this loss is brought down to eight per cent. (8%) theo- 
retically, and perhaps to three or five per cent. (3% or 5%) in practice. As 
higher pressures are used, the gain by compounding is greater. 



FIRING. 

Ignition in compressed air pipes, commonly known as firing, was referred 
'jefore in these columns. We are not satisfied that the question has been 
thoroughly ventilated, hence further discussion of the subject seems advisable. 
Compressed air claims to be and is a safe power. Occasionally we hear of a 
case of firing, which to some may appear to be a serious objection to the use of 
air; but if the causes are known and understood, and due care observed, firing 
becomes merely a matter of carelessness. A building made of wood is not con- 
sidered unsafe because it will burn when ignited. Compressed air is not inflam- 
mable, but during compression by mechanical means, it is found advisable to use 
oil, and this oil, or the gases from it, are the sources of combustion. In most 
crses firing may be traced to the use of poor oil, but in others too much oil some- 
times causes ignition. It is a common mistake of engineers in charge of com- 
pressors to feed oil too rapidly to the air cylinder. It is simply necessary to sup- 
ply oil enough to keep the interior of the cylinder and the moving parts moist- 
ened. Where steam is used there is a tendency to cut away the oil, hence engi- 
neers grow accustomed to feeding a larger supply than is required in an air 
cylinder. There is nothing to cut or absorb the oil in the air end; in fact, it is 
only after a considerable lapse of time that oil can get away when fed into the 
cylinder. There is no washing tendency as with steam, and a drop now and 
then is all that is required to keep the parts lubricated. Where too much oil 
is used, there is a gradual accumulation of carbon, which interferes with the 
free movement of the valves and which chokes the passages, so that a high tem- 
perature may for a moment be formed and ignition follow. It is well to get the 
best oil, and to use but little of it. 

There are cases where firing has arisen from the introduction of kerosene 
or naphtha into the air cylinder for the purpose of cleaning the valves and cut- 
ting away the carbon deposits. Every engineer knows how easily he may clean 
his hands by washing them in kerosene ; and as this oil is usually available, we 
have seen men introduce, it into the air cylinder through a squirt-can at the 
inlet valve. This is a very effective way of cleaning valves and pipes, but it is a 
source of danger, and should be absolutely forbidden. High grade lubricating 
oils are carefully freed of all traces of benzine, naphtha, kero.^cne and other light 
and volatile distillates. The inflammability of such oils is so acute that it is a 
dangerous experiment to introduce anything of this kind into an air cylinder; 
and if any of our readers have had an explosion in a case where the engineer 
uses kerosene, it may be traced to this source. Closed inlet passages leading to 
the air cylinder through which the free air is drawn from outside the building 
have many advantages, but one seldom thought of is that they interfere with the 
fendency of the engineer to squirt kerosene in(Q the cylinder. 



146 PRODUCTION. 

Soft soap and water is the best cleanser for the air cylinder, and it is 
recommended even in cases where the best oil is used. Long service will result 
in more or less accumulation of carbon; hence it is advised that engmeers, once 
or twice a week, or oftener if necessary, fill the oil cup with soft soap and water 
and feed it into the cylinder as the oil is fed. 



FIRING. 

Our attention has been attracted to a case where a receiver took fire on the 
inside repeatedly. On examination it was found that the drain had only let the 
water off, leaving a sediment of oil. This was immediately cleansed and the drain 
enlarged, but it did not, however, remedy the cause of complaint, although it 
improved matters somewhat. 

On asking for advice, they were told that there was something abnormal 
about the condition of the plant, and were advised to resort to means of cleaning 
out the compressor and receiver at least once a month, investigating the air 
compressor to see if the valves were not clogged up, thus causing an excessive 
temperature in the air cylinder. They were then recommended not to use oil 
for one day, but instead to use soap suds in the air cylinder, admitting them by 
the regular lubricator. This would clean out the cylinder. Next a good grade 
of air cylinder oil should be secured, and only a proper amount of it used— say 
one drop per five minutes. 

These instructions remedied the trouble almost immediately, and we quote 
the fact thinking the matter might prove of some interest to our readers in 
general. 



The Clifton Colliery Co., Ltd., 

Nottingham, Eng., June 29, 1897. 
Editor Compressed Air: 

Dear Sir: — I notice in Compressed Air that you invite correspondence 
from engineers and others interested in compressed air. We have a pair of air 
compressing engines, cylinders 30 inches diameter by 4 ft. stroke, working at a 
pressure of 60 lbs. per square inch. The point I particularly wish to bring to 
your notice is that we have had two explosions in the air cylinders, which is be- 
lieved to have been caused by the oil used for lubricating the pistons in the 
cylinders vaporizing and then getting ignited by the high temperature produced 
by the compression of the air. The oil used was guaranteed to have a flash 
point of 554" F., and ignition point of 606° F. There have been four other sim- 
ilar explosions with air compressing engines at various collieries in this coun- 
try. Have you had any other explosions of this kind brought to your notice, and 
if so, has the cause been made out? If the cause of these explosions could be 
cleared up it would be very interesting and useful information to users of air 
compressing engines. If the cause be really due to the oil vaporizing and thei> 
becoming ignited, it will be necessary, to prevent explosions from this cause, 
to use some other material in lieu of oil for lubricating the pistons, or to adopt 
some other and more effective means of cooling the air during compression, to 



PRODUCTION. 147 

prevent such high temperatures being produced as will vaporize oil. If you are 
able to throw any light on this matter, you will greatly oblige, 

Yours faithfully, Henry Fisher. 

Ignition in compressed air discharge pipes and passages is not uncommon 
in America. At times this ignition is in the nature of an explosion. Two Air 
Receivers were blown up during the construction of the New York Aqueduct, 
in one case the engine room was destroyed by fire resulting from this explosion. 
We have also records of two other cases where spontaneous explosions in the 
Air Receiver have resulted in the destruction of the engine room by fire. Other 
instances occur where ignition takes place near the Air Compressor, the pipes 
becoming red hot at the joints. This ignition has been known to extend into thf^ 
Air Receiver, and in one instance, the flames were carried down into the mine by 
the compressed air. 

In all such cases large volumes of compressed air were used. It is plaia 
that the cause of the explosion or ignition is an increase of temperature above 
the flash point of the oil which is used to lubricate the Compressor. A thick 
or cheap grade of cylinder oil should never be used in an Air Compressor. Thin 
oil which has a high flash point and which is as free from carbon as conditions 
of lubrication will admit, is the best oil. Our correspondent calls attention to 
explosions where the flash point of the oil is 554 degrees F., and ignition point 
606 degrees F. We know of an instance where ignition took place with oil which 
had a flash point of 575 degrees F., ignition point 625 degrees F. Conditions 
were similar to those mentioned by our correspondent, that is the air was com 
pressed'to about 60 lbs. per sq. in. gauge pressure. If the temperature of the air 
before admission to the Compressor is 60 degrees F., and it is compressed to 58.8 
lbs. gauge pressure, the final temperature, where no cooling is used during com- 
pression, will be 369.4 degrees F., or a total increase of 309.4 degrees. If air is 
admitted at 60 degrees F., is compressed without cooling to 73.5 lbs. gauge pres- 
sure, the final temperature will be 414.S degrees F., and the total increase of 
temperature 354.5 degrees. Under such circumstances the question naturaPy 
arises how is it possible when using oil with an ignition point of over 600 degrees 
to get an ignition, especially as water jackets and other methods of cooling 
are used which should reduce the final temperature? The figures are also based 
on dry air which increases in temperature during compression to a greater de- 
gree than moist air, and it is known that air that is used in compressors is never 
very dry. The theoretical figures show that in order to get ignition with the oil 
mentioned, the gauge pressure should be about 200 lbs. per sq. in., where no cool- 
ing takes place. 

It is plain that there must be an increase of temperature or ignition would 
not take place. This increase of temperature may result either from an increase 
of pressure which is not recorded on the gauge, or there may be an increase of 
temperature without a corresponding increase of pressure. Take the first in- 
stance, and it is not difficult to understand that an air compressor might deposit 
carbon from the oil in the discharge passages or discharge pipes which in the 
course of time will accumulate and constrict the passages so that they do not 
freely pass the volume of air delivered by the compressor, hence a momentary in- 
crease of pressure might exist in the cylinder heads or in the discharge pipe 



148 PRODUCTION. 

which leads from the air cylinder to the receiver; this momentary increase ol 
pressure would surely carry with it an increase of temperature which might ex- 
ceed the ignition point of the oil. A badly designed compressor with inefficient 
discharge passages might produce this trouble. Too small a discharge pipe or 
too many angles in discharge pipes might also tend to produce explosions. But 
we have known instances where ignition has occurred in a well designed system, 
hence we must look for other causes. In our judgment the majority of cases 
may be traced to an increase of temperature without an increase of pressure; 
this increase of temperature can only be excessive where the temperature of the 
incoming air is excessive. A hot engine room from which air is drawn into the 
cylinder is a bad condition. We have known cases where the incoming air was 
drawn from the neighborhood of the boiler, the temperature being close to i.-^o 
degrees F. This means, of course, that if the total increase of temperature when 
air is compressed to 73.5 lbs. gauge pressure is 354.5 degrees, the temperature 
of the initial air should be added to this figure and that the final temperature 
might be 504.5 degrees. 

But we have known ignition to take place when the temperature of the in- 
coming air was normal, when the discharge passages and pipes were free and 
pf ample area, hence we must look for some other cause. The only possible ex- 
planation is that the temperature of the incoming air is made excessive by the 
sticking of one or more of the discharge valves, thus letting some" of the hot 
compressed air back into the cylinder to influence the temperature before com 
pression. When a piston of an air compressor has forced a cylinder volume of 
air through the discharge valve, and when this piston has its direction of move- 
ment reversed there will immediately be a tendency of the air just compressed 
and discharged to return to the cylinder. In this it is checked by the discharge 
valve, but through long and constant use these discharge valves become encrusted 
with carbon and are not free to move, hence there may be a moment when one of 
these valves sticks, or it may not seat properly; in either case there will be some 
hot compressed air in the cylinder when the piston starts on its return stroke 
of compression, the air may have lost its pressure, but not its temperature, and 
it is not difficult to understand a leaky discharge valve letting enough air back 
into the cylinder to increase the initial temperature to two or three hundred de- 
grees. If so, and we are compressing air to 73.5 lbs. gauge pressure we have 
say 300 degrees temperature in the free air before compression, and as the in- 
crease is 354.5 degrees, the resulting temperature might be 654.5 degrees. 

As a remedy we would suggest more care in selecting the best air com- 
pressor and in frequent cleaning of the discharge valves and passages. The best 
air compressors are built so that the discharge valves may be readily removed: 
these valves should be cleaned regularly once a week by the engineer, who should 
make sure that they fit properly. It is impossible to get good lubricating oil that 
is free from carbon, liencc there will always be more or less carbon deposited 
on the discharge valves, but this must not be allowed to accumulate. 

Inter-coolers between air cylinders and after-coolers between final cylinder 
and receiver are also recommended. The best inter-coolers are made of nests of 
brass tubes, the air passing around the tubes and the water through them, hence 
there is a thorough splitting up of the air and efficient cooling. One of these 



r 



PRODUCTION. 149 



coolers located in the discharge pipe will absolutely prevent the passage of flame 
and will insure the protection of the mine against fire even though there be igni- 
tion at or near the air cylinder. 



AN EXPLOSION IN THE RECEIVER OF AN AIR COMPRESSOR. 

The past occurrences of explosions in air compressors receive additional 
interest from the fact that an explosion has lately taken place in the receiver of 
an air compressor in Saxony, while one also occurred in the air compressing 
engines at the Clifton colliery, near Nottingham. The Gluckauf report gives the 
following as the probable cause of the explosion : In the valve-chest of the air 
cylinder, on the slide valves and on the inner surface of the compressed air pipes, 
a soot-like residue was found, the origin of which must evidently be referred to 
the employment of the lubricant; and this residue showed traces of coke forma- 
tion, thus leading to the conclusion that ignition and combustion must have 
occurred. This view of the question is strengthened by the circumstances that 
the residue entered into partial combustion after the explosion, and that previous 
ignitions of the lubricant, owing to heating of the engine slide-valves, had been 
observed. The lubricant possesses in common with other organic substances, the 
property of decomposing at high temperatures, forming gaseous products consist- 
ing of hydrocarbons with resinous residue. The incrustation on the valve-chest 
of the air cylinder and the compressed air pipes proves that such chemical changes 
took i^lace owing to high temperatures. The gaseous constituents thus formed 
must have passed, with the compressed air, into the receiver, and have formed 
there, as well as in the pipes and valve-chests, a highly explosive gaseous mixture 
which, on being ignited, was capable of causing a very violent explosion. The 
action of such an explosion must have been so much the more intense as the 
gaseous mixture was subject to a pressure of nearly 4^ atmospheres (70 lbs. per 
square inch) over that of the atmosphere; and this high pressure affords an ex- 
planation of the unusually violent mechanical action manifested. 

As is evident from the above explanation, the explosion must have originated 
in the lubricant, and, owing to the great importance of the question, it appeared 
necessary to determine the composition and also the flashing point of the lubricant 
employed — which was done at the Royal Testing Station, Berlin. The tests showed 
the lubricant in question to be a good one and suitable for the purpose for which 
it was employed. The specific gravity was found to be 0.89 at a temperature of 15° 
(^•(59° F.), while it was proved to be free from animal and veg'etable fat and to con- 
sist of hydro-carbons which have taken up only a small quantity of oxygen. The 
ignition point, on the lubricant being heated in open crucibles, is near upon 291° C, 
the boiling point being 375° C. "This lubricant, is, therefore," states the report, 
"entirely free from hydrocarbons of low boiling point, and consists of hydrocar- 
bons differing so little from one another that great care must have been exercised 
in its production." If such an oil be allowed to drop into red-hot retorts it will 
become decomposed, like all other organic substances, and form gaseous products 
as well as more or less coke; and, by the evaporation of 20 grammes (2-3 oz.) 
of such an oil, about i cubic metre (35 cubic feet) of air may be rendered cx- 
plosible. If now, notwithstanding this property of the lubricant, so considerable 



150 PRODUCTION. 

a fatty residue as that described was found in the valve-chests, this circumstance 
proves that, in consequence of the insufficient cooling down, and consequenth- 
great elevation of temperature, considerable quantities of the oil were gradually 
decomposed in the valve-chest ; and this decomposition, with simultaneous forma- 
tion of an explosive gas, was favored by the large surface of the valve-chest and 
the comparatively large quantity of oxygen drawn in. Consequently, the acciden. 
must be attributed primarily to insufficient cooling down of the valve-chests. — 
Colliery Guardian. 



EXPLOSIONS AND IGNITIONS IN AIR COMPRESSORS AND RE- 
CEIVERS.* 



BY ALFRED GEORGE WHITE. 



The attention of engineers in this and other countries has from time to time 
been drawn to the results of explosions which have occurred in air compressors 
and receivers. In some cases the cause has been ascertained; but so far as the 
author is aware, no systematic investigation of the subject has been made with a 
view to obviate the disastrous results of explosions and ignitions, which the 
author believes to be more frequent than is generally known. The following ac- 
count of a recent occurrence of this nature which came under the author's notice, 
with a description of the compressor, may help to throw light on the subject. 

The air compressor was employed for the purpose of supplying air to rock 
drills and hoisting engines in a copper mine in Norway. The usual working 
pressure being between 50 and 60 lbs., the safety valve of the receiver was loaded 
to blow off at the latter pressure. It had been continuously at work for seventeen 
years, and was of English make, with two horizontal air cylinders 24 in. in 
diameter and 36 in. stroke. The motive power was supplied by a high-speed tur- 
bine on a horizontal shaft, upon which a pinion was keyed, gearing with a spur 
wheel on the compressor driving shaft. On this shaft also there were keyed a 
heavy fly-wheel and two crank discs, which worked the air-cylinder pistons by 
means of connecting rods in the usual way The inlet valves were plain circular 
valves with stems, four being placed in each cover of the air cylinders. Bell- 
crank levers fitted with counterweights were attached to the valve stems for 
closing the valves at the end of each stroke before compression commenced, the 
atmospheric pressure opening them simultaneously during the inward or inspira- 
tion stroke. The outlet valves were of the ball type, of solid brass, fitted in brass 
seats, two on each delivery port on the top of the cylinders, their action being 
regulated by the pressure of air in the cylinders and receiver. 

The cooling arrangements consisted of an open water jacket round each 
cylinder, the water supply being admitted near the surface on one side and dis- 
charged through an overflow pipe of ^ in. bore on the other side at the same 
level. The water surrounded the cylinders and air delivery ports, and stood 
about I in. deep over the latter. The water supply and discharge being placed 

* Excerpt transactions Inst. C. E. 



PRODUCTION. 151 

at the same level near the top, the water simply flowed over the surface and did 
not circulate round the cylinder. It will thus be seen how imperfect the cooling 
action was in this instance. 

The oil used in lubricating the air cylinders was composed of crude fish 
oil and tallow mixed together, and was put into the cylinders through the inlet 
valves by a common oil can. The lubrication therefore depended entirely on 
the attention and skill of the attendant, and no doubt at times a greater or less 
quantity of oil was poured into the cylinders than was required, and any surplus 
was driven out through the delivery valves into the air pipes and receiver. 

The air receiver, placed inside the compressor-house, consisted of a 
wrought-iron cylinder about 20 ft. long by 4 ft. 6 in. in diameter, and was con- 
nected to the air cylinders by an 8 in. cast-iron pipe. This pipe had an ordinary 
spigot and socket joint on the horizontal portion between the receiver and 
compressor. The joint was made of lead, run in and caulked, but owing to the 
contraction and expansion of the pipe it leaked, and had to be renewed from time 
to time. On the day of the ignition, and shortly before its occurrence, this joint 
had been renewed by running molten lead against a hempen gasket, and very 
soon after the compressor was started, flames blew out in great volume from the 
safety valve on the air receiver. The attendant succeeded in stopping the com- 
pressor within a few moments, but the flames continued for some time and set 
fire to the compressor-house, which was built of timber, and in the course of half 
an hour, it was burnt to the ground. 

The author considers the cause which led to the fire breaking out in the 
receiver to have been the ignition of the oil accumulated there and the use of 
molten lead in making the spigot joint of the pipe referred to, by which the oil 
must have been first ignited in the pipe. On starting the compressor, the draught 
of air created would cause the ignited oil in the pipe to set fire to the oil in the 
receiver, or the fire may have already spread to the receiver. The products of the 
decomposition of the large quantity of oil in the receiver would, in conjunction 
with the air, form an explosive mixture, which, failing relief through the safety 
valve, might have resulted in an explosion. The cause of all explosions and 
ignitions of this nature can be traced to these phenomena. The case which 
occurred at the Westphalia Colliery in 1896 resulted in destruction of the air 
receiver by bursting. In the present instance the rise of pressure does not 
appear to have been sudden enough to burst the receiver, and the relief afforded 
by the safety valve averted this catastrophe. When the receiver was opened it 
was found to contain a quantity of charred oil in the form of a sticky paste about 
2 in. deep in the bottom. The air pipes were coated inside with a similar sub- 
stance. The damage done to the compressor and receiver was, however, con- 
siderable, the riveted joints of the latter being started and the lead joints of the 
contiguous pipes and connections melted out. One cylinder of the compressor 
and one crank disc was cracked, as also were two arms of the turbine, which 
was placed inside the house burnt down. The latter effects were chiefly due to 
the subsequent fire and the water which was thrown upon the heated metal. 

The primary cause of this fire was the accidental ignition of the oil by the 
admission of molten lead into the pipe referred to, but the same effect may be 
produced by an increase of air pressure, and consequently of temperature, to a 



152 



PRODUCTION. 



point at which the decomposition of the oil and ignition of the air and gas mix- 
ture take place, or by the admission of coal dust or inflammable matter into the 
valves or cylinders of the compressor. The use of oils possessing low-flashing 
temperatures and the increase of temperature from friction of metallic surfaces 
improperly lubricated are also elements of danger, besides defective water- 
jacketing and cooling arrangements. 

The temperature of air compressed adiabatically to 58.8 lbs. per square 
inch gauge pressure from 60° F. initial temperature is 270° F. The air admitted 
to a compressor is, however, sometimes at a much higher temperature than 60° 
F., and may in some instances be as high as 100° F. ; the temperature of this air 
when compressed to 58.8 lbs. per square inch gauge pressure will rise to about 
430° F., and when compressed to 75 lbs. per square inch, the final temperature is 
nearly 500° F. This shows the importance of ( i ) a low initial air temperature ; 
(2) adequate cooling of the air before or during compression; and (3) the use 
of lubricating oils of high-flashing and ignition points. 

A similar ignition to the one mentioned by the author occurred in 1897 
in the Clifton Colliery air receiver, and tests were made of the oil then in use, 
giving the following results :t — 

FlasliinK Point. Isjnition 

Close Test. Point. 

Sample No. 1 454^ F. 594« F. 

Sample No. 2 460° F. 588« F. 

Lubricating oils of high-class manufacture, distilled from petroleum and 
used for high-pressure steam engines, give flashing points of from 530 to 560° 
F. (open test), and ignition points of from 600 to 630° F. It is, however, some- 
times the case that oils having a high flashing point are mixed with others having 
a much lower one, and therefore a guarantee should be demanded, or a test of 
the oil should be made. The flashing point of the oil used in the compressor 
described by the author, taking that of Arctic sperm, would be only 446° F. 

It is evident that, given reliable oil of high-flashing point and normal 
conditions of working for a well-designed air compressor, the danger of ignition 
is practically eliminated, as shown by the following table: — 

TABLE 15. 



Working 
Pressure of Air. 


Initial 

Temperatui e 

of Air. 


Final 
Temperature 

of Air 

Compressed 

Adiabatically. 


High Tempeeatuke Oil. 


Flashing 
Point. 


Ignition 
Point. 


Lb. per 
Square Inch. 

58.8 
58.8 
75.0 


60 
100 
100 


°F. 

370 
435 j 
500 j 


^F. 
530 

560 


op, 

600 
680 



The final temperature of the air will, of course, be diminished when the 
air is cooled during compression, in proportion to the efficiency of the cooling 
+ TranBactions of the Federated Institution of Mining Engineers, vol. xiv., part 4. 



PRODUCTION. 153 

apparatus ; and in hot countries, where the initial temperature of the air is 
high, the addition of an apparatus for cooling the air prior to admission to the 
compressor, in addition to other cooling arrangements, would be attended with 
economical and advantageous results. 

With reference to the design of air compressors, the author is of opinion 
that the following points require special attention: — (i.) The arrangement of 
the air admission to the compressor in such a manner that the lowest possible 
initial temperature is obtained, and the air protected from all dust or inflammable 
matter and sparks. (2.) Efficient water-jacketing of the air cylinders by closed 
jackets, with water supply under pressure, and, in case of double-stage com- 
pressors, an intermediate cooler of adequate capacity. (3.) The more general 
adoption of compound or double-stage compressors with intermediate coolers, 
whereby a more effective cooling of the air and greater economy of power are 
attained. (4.) The employment of automatic lubricators on the air cylinders. 
(5.) The use of pyrometers, whereby the temperature of the air in each cylinder 
and in the receiver can be seen by the attendant. (6.) The reduction of 
clearance at the ends of the cylinders and of the valves ports to a minimum. 
(6a.) The design of valves having definite action without friction in working, 
of ample area and readily removable for inspection or cleaning. (7.) The use 
of tested oils having high flashing points. (8.) Proper arrangements for 
draining and blowing off accumulated oil in both air receiver and pipes. 

About two years previous to the ignition described by the author, an 
explosion occurred in one of the cylinders of the same compressor, resulting in 
destruction of the cylinder. The cause of this was not ascertained at the time, 
but it was probably due either to excessive friction in the cylinder or defective 
action of the valves, causing an increase of temperature and consequent decom- 
position of the oil, or to an increase in the air pressure sufficient to burst the 
cylinder. 

The production of fire by means of the sudden compression of air is 
known to the aborigines of the Philippine Islands, who employ a small tube fitted 
with a plunger, which, on being sharply struck, ignites combustible matter placed 
at the bottom of the tube. 



EXPLOSIONS IN AIR. 

A serious accident occurred recently in the Tintic District at the Mammoth 
Mine, Mammoth, Utah. An explosion occurred in the air cylinder of a Duplex 
Corliss Compressor. The accident was very severe, resulting in the death of the 
Assistant Engineer, Mr. Charles Meranda, and injury to the Chief Engineer, Mr. 
William Nesbit. The cause of the explosion has been attributed to the oil in the 
cylinders. The explosion was terrific; the back head was shattered, while the 
back flange of the cylinder was torn off at several points, particularly at the top, 
where a portion of the cylinder was blown away. 

At the time of the explosion the Chief Engineer, Mr. William Nesbit, was 
kneeling in front of the cylinder manipulating the inlet valve pin, while his 
assistant, Mr. Charles Meranda, was standing close by. Meranda was hurled 
under a work-bench about 10 ft. distant, badly mangled, while Nesbit struck the 



154 PRODUCTION. 

wall in an unconscious condition. These two men were alone in the engine 
room at the time, and we understand that when Nesbit regained consciousness he 
realized that the compressor was running away and staggered to the throttle, 
falling down three or four times in attempting to shut off the steam, which he 
finally did, thus preventing the destruction of the compressor, as the governor 
was rendered useless by the explosion. Parts of the cylinder head tore out a 
window and shot 50 or 60 feet beyond the building, and we hear that a piece of 
Meranda's thigh flesh, the size of your two fists, was found on an ore dump 150 
feet away. At the time of the accident they were compressing air to 80 pounds 
at about 60 R. P. M. 

Such explosions fortunately are rare in air compressor service, and they 
serve to emphasize the importance of using only the best grade of air cylinder oil. 
Cheap oil has no place in air passages and even with the best oil, explosions may 
occur if too much oil is fed into the cylinder and if sufficient care is not taken to 
keep the valves and ports clean and free from oil deposit. A form of kerosene 
engine is made to act on the principle which is illustrated by explosions in the 
cylinders of air compressors. This oil engine has a chamber which is at first 
warmed by the heat of a lamp applied externally. After there is sufficient heat to 
cause the explosion of the kerosene, the lamp is removed and the temperature of 
the chamber is sufficient to continue these explosions at each return stroke of the 
piston, which forces hot compressed air in contact with this oil vapor. Here 
is an engine acting on the explosive principle similar to that in use in all oil 
engines, yet there is no spark or other direct means of ignition. In the cylinder 
of an air compressor as the piston approaches the head it compresses the air to a 
point which in both pressure and temperature is sufficient to cause an explosion 
provided there is oil vapor present, the flashing point of which is about the same 
as the temperature in the cylinder. This flashing point of oil is something of a 
mystery when the oil is used in compressed air. Ordinarily, the flashing point of 
oil can be easily determined, but when used in compressed air, either the oil is dis- 
associated and separated into component parts or its flashing point is lowered 
by contact with the heavily oxygened air chamber. Sufficient importance is not 
given to the water jackets as a means of preventing explosions. In the case of 
the oil engine referred to the heat of the cast iron effects the explosion and in an 
air cylinder we have a similar condition in the shape of a hot cast iron cylinder 
or head. It is not sufficient to water jacket the cylinder only, but if the heads are 
not jacketed they are likely to become hot and to materially aid in causing explo- 
sions. This is especially true where the air is used at high pressures, and where 
the compressor is run at high speed. It is merely necessary to put one's hand 
upon the head of an air cylinder in the engine rooms where compressors are used, 
to note that this piece of metal is very hot. 



EXPLOSIONS. 



Continuing the important subject of explosions in compressed air pas- 
sages, which was alluded to in our last issue, we are convinced that in some cases 
the cause of the explosion may be attributed to the fact that one or more of the 
discharge valves fails to close at the end of the stroke of the air compressor, and 



r 



PRODUCTION. 155 

thus a portion of the hot compressed air from the receiver is let back into the 
cylinder. The result of this is that when the piston returns for another stroke of 
compression it acts against a cylinder full of hot compressed air, both temperature 
and pressure being higher than normal. It is quite possible that the discharge 
valve which has admitted this hot air may close before the return stroke of the 
piston. Hence, we have bottled up in the cylinder an unnatural condition of 
things, which will result in a temperature higher than normal as soon as this air 
has been compressed to receiver pressure. If we admit air into the cylinder of 
the compressor at a temperature of 60 degrees F., and at normal atmospheric 
pressure, this temperature will reach about 415 degrees F. when the gauge 
registers 75 lbs., thus showing an increase of temperature of 355 degrees. Now, 
it is a well known fact that all good air compressors have cooling devices, such as 
water jackets, for the purpose of keeping down this temperature during com- 
pression, but it is also quite as well known among those who had had experience 
in this matter that in large cylinders these water jackets have very little cooling 
effect. Hence, in air compressor cylinders, as usually made, we may expect 
approximately the large increase of temperature hereinbefore mentioned. To 
illustrate this still further, when a volume of air is compressed without cooling 
to 21 atmospheres (294 lbs. gauge pressure) it will occupy a volume a little more 
than one-tenth. The total increase of temperature, assuming that we start at 
an initial temperature of zero, is about 650 degrees ; but if we start with an initial 
temperature of 60 degrees, the total increase is about 800 degrees, and if we start 
with 100 degrees initial temperature the increase is 900 degrees. When free air 
is admitted to a compressor cold, the relative increase of temperature during 
compression is less than when the air is admitted hot. This being the case, we see 
how important it is to admit air to the cylinders of an air compressor at low 
temperature, for a high initial temperature means a greater increase of tem- 
perature throughout the stroke; and only a slight defect in a discharge valve 
might result in the destruction of the machine, because of the admission of a 
small quantity of hot compressed air, thus raising the temperature in the cylinder 
beyond the flashing point of the oil. We are inclined to think that a leaky dis- 
charge valve is responsible for many serious accidents in air compressor ser- 
vice, and this points to the importance of the discharge valve as a feature of the 
air compressor. It should be designed in such a way as to at least minimize the 
liability of sticking or leaking. Even with the best form of discharge valve 
trouble may arise because of the use of bad oil or of too much good oil. Engi- 
neers are apt to suppose that an air cylinder of a compressor requires oil just as 
a steam cylinder does. This is a mistake. Too much oil results in obstruction 
of the parts and passages, and through the heat a carbon deposit is formed, which 
causes sticking. This carbon deposit is nothing more than what will result if 
oil is placed on a hot shovel and allowed to evaporate, except that in the cylinder 
of an air compressor this evaporation process is going on all the while, and in 
the course of time a hard, black deposit is formed which interferes with the 
proper working of the parts. Some engineers find out that this deposit is easily 
cut away by kerosene oil, and in their anxiety to take the quickest way to remedy 
the difficulty they throw kerosene oil into the inlet valve — a course which some- 
times proves to be the surest way out of all earthly difficulties. Kerosene oil has 



156 PRODUCTION. 

a flashing point of 120 degrees F., and it is not difficult to understand what the 
cause of the explosion is under such circumstances. 

Air compressors should be provided with discharge valves that are easily 
accessible and engineers in charge of the plants should clean out all discharge 
valves and passages at least once a week. Care should also be taken to use a 
good grade of non-carbonizing oil of a high flashing point, and to use very little 
of it ; one drop every five minutes is enough. Care should also be taken to see that 
the pipes and passages leading from the discharge valves to the receiver are large 
and accessible. The receiver itself should be provided with a man-hole and be 
cleaned out at regular intervals. If, as we have found in some cases, the trouble 
continues to exist, except that it is now transferred to the pipe line, our next 
remedy should be to place an after cooler at the receiver, and in this way reduce 
the temperature of the air to normal condition before it is started on its journey. 
This is invariably done in pneumatic service, such as switching and signaling 
work, where it is important to maintain uniform conditions in the air pipe and^ 
where dry air is essential. This after cooler is nothing but a surface condenser, 
which reduces the temperature of the compressed air, causing it to deposit its 
moisture. There can be no trouble from explosions in a pipe line equipped in 
this way, and where these lines are long, and where the pipe is laid under ground, 
the after cooler serves also to prevent much trouble from expansion and con- 
traction. Air pipes laid on the surface in an irregular way over the gtound will 
usually adjust themselves to changes of temperature, but if boxed up or buried 
the joints are apt to give trouble, unless allowance is made for expansion and 
contraction, and this is minimized where the compressed air, after leaving the 
receiver, is brought down to normal conditions. 



AIR COMPRESSOR EXPLOSIONS.* 



By Alfred George White. 



EXPLOSION IN A COPPER MINE. 

The air compressor was employed for the purpose of supplying air to rock 
drills and hoisting engines in a copper mine in Norway. The usual working pres- 
sure being between 50 and 60 pounds, the safety valve of the receiver was loaded 
to blow off at the latter pressure. It had been continuously at work for seventeen 
>ears, and was of English make, with two horizontal air cylinders, 24 inches in di- 
ameter and 36 inches stroke. The motive power was supplied by a high-speed 
turbine on a horizontal shaft, upon which a pinion was keyed, gearing with a spur 
wheel on the compressor driving shaft. On this shaft also there were keyed a 
heavy flywheel and two crank disks, which worked the air-cylinder pistons by 
means of connecting rods in the usual way. The inlet valves were plain circular 
valves with stems, four being placed in each cover of the air cylinders. Bell-crank 
levers fitted with counter-weights were attached to the valve stems for closing the 
valves at the end of each stroke before compression commenced, the atmospheric 
♦Abstract from British Institute Civil Engineers. 



PRODUCTION. 157 

pressure opening them simultaneously during the inward or inspiration stroke. 
The outlet valves were of the ball type, of solid brass, fitted in brass seats, two on 
each delivery port on the top of the cylinders, their action being regulated by the 
pressure of air in the cylinders and receiver. 

The cooling arrangements consisted of an open water jacket round each 
cylinder, the water supply being admitted near the surface on one side, and dis- 
charged through an overflow pipe of ^-inch bore on the other side at the same 
level. The water surrounded the cylinders and air-delivery ports, and stood about 
I inch deep over the latter. The water supply and discharge being placed at the 
same level near the top, the water supply flowed over the surface and did not cir- 
culate round the cylinder. It will thus be seen how imperfect the cooling action 
was in this instance. 

The oil used in lubricating the air cylinders was composed of crude fish oil 
and tallow mixed together, and was put into the cylinders through the inlet valves 
by a common oil can. The lubrication, therefore, depended entirely on the atten- 
tion and skill of the attendant, and no doubt at times a greater or less quantity 
of oil was poured into the cylinders than was required, and any surplus was 
driven out through the delivery valves into the air pipes and receiver. 

The air receiver, placed inside the compressor-house, consisted of a wrought- 
iron cylinder about 20 feet long by 4 feet 6 inches in diameter, and was connected 
to the air cylinders by an 8-inch cast-iron pipe. This pipe had an ordinary spigot 
and socket joint on the horizontal portion between the receiver and compressor. 
The joint was made of lead, run in and caulked, but owing to the contraction and 
expansion of the pipe it leaked, and had to be renewed from time to time. On the 
day of the ignition, and shortly before its occurrence, this joint had been renewed 
by running in molten lead against a hempen gasket, and very soon after the com- 
pressor was started, flames blew out in great volume from the safety valve on the 
air receiver. The attendant succeeded in stopping the compressor within a few 
seconds, but the flames continued for some time and set fire to the compressor- 
house, which was built of timber, and in the course of half an hour it was burned 
to the ground. 

WHAT CAUSED THE EXPLOSION. 

The author considers the cause which led to the fire breaking out in the re- 
ceiver to have been the ignition of the oil accumulated there and the use of molten 
lead in making the spigot joint of the pipe referred to, by which the oil must have 
been ignited in the pipe. On starting the compressor, the draught of the air created 
would cause the ignited oil in the pipe to set fire to the oil in the receiver, or the 
fire may have already spread to the receiver. The products of the decomposition 
of the large quantity of oil in the receiver would, in conjunction with the air, form 
an explosive mixture, which, failing relief through the safety valve, might have 
resulted in an explosion. The cause of all explosions and ignitions of this nature 
can be traced to these phenomena. The case which occurred at the Westphalia 
Colliery in 1896, resulted in the destruction of the air receiver by bursting. In the 
present instance the rise of pressure docs not seem to have been sudden enough to 
burst the receiver, and the relief afforded 1)y the safety valve averted this catas- 
trophe. When the receiver was opened it was found to contain a quantity of 



158 PRODUCTION. 

charred oil in the form of a sticky paste about 2 inches deep in the bottom. The 
air pipes were coated inside with a similar substance. The damage done to the 
compressor and receiver was, however, considerable, the riveted joints of the latter 
being started and the lead joints of the contiguous pipes and connections melted 
out. One cylinder of the compressor and one crank disk were cracked, as also 
were two arms of the turbine, which was placed inside the house burned down. 
The latter effects were chiefly due to the subsequent fire and the water which was 
thrown upon the heated metal. 

The primary cause of the fire was the accidental ignition of the oil by the 
admission of molten lead into the pipe referred to, but the same effect may be pro- 
duced by an increase of air pressure, and consequently of temperature, to a point 
at which the decomposition of the oil and ignition of the air and gas mixtures 
takes place, or by the admission of coal dust or inflammable matter into the valves 
or cylinders of the compressor. The use of oils possessing low-flashing temper- 
ature from friction of metallic surfaces improperly lubricated is also an element 
of danger, besides defective water- jacketing and cooling arrangements. 

A similar ignition to the one mentioned by the author occurred in 1897 in the 
Clifton Colliery air receiver, and tests were made of the oil then in use, giving 
the following results: 

Flashing Point Ignition 

Close Test. Point. 

Sample No. i 454° Fahr. 594° Fahr. 

Sample No. 2 460° Fahr. 588° Fahr. 

Lubricating oils of high-class manufacture, distilled from petroleum and used 
for high-pressure steam engines, give flashing points of from 530 to 560 degrees 
Fahr. (open test), and ignition points of from 600 to 630 degrees Fahr. It is, 
however, sometimes the case that oils having a high flashing point are mixed with 
others having a much lower one, and therefore a guarantee should be demanded, 
or a test of the oil should be made. The flashing point of the oil used in the 
compressor described by the author, taking that of Arctic sperm, would be only 
446 degrees Fahr, It is evident that, given reliable oil of high-flashing point and 
normal conditions of working for a well-designed air compressor, the danger of 
ignition is practically eliminated. 

About two years previous to the ignition described by the author, an explo- 
sion occurred in one of the cylinders of the same compressor, resulting in the de- 
struction of the cylinder. The cause of this was not ascertained at the time, but 
it was probably due either to excessive friction in the cylinder or defective action 
of the valves, causing an increase of temperature and consequent decomposition 
of the oil, or to an increase in the air pressure sufficient to burst the cylinder. 



New York, Aug. 19, 1897. 
Editor Compressed Air: 

Dear Sir: We have before us your issue of July, 1897, and in it we note 
remarks in reference to ignition in air cylinders of air compressors. This to us 
is a very interesting subject, and, as you know, we have devoted a great deal of 



r^;r;^iy--'f 



PRODUCTION. 159 



time and money to it, and we are glad to place before you some few facts which 
may interest your correspondents. 

That the occasional occurrence of fire in air compressors is due to the oil 
present, there can be no doubt, as the oil is the only substance present which can 
bum ; and in this connection we beg to say that the cause of this difficulty cannot 
be laid to the oil alone, although it is a well-known fact that an inferior oil which 
contains a large amount of carbon and other foreign substances can readily cause 
explosions. 

That certain structural features of a given machine may facilitate or retard 
combustion of the oil, will, we think, appear from what follows : 

The fact of an air compressor drawing the air from whatever location the 
compressor may be in, naturally necessitates the presence in the air cylinder of 
whatever foreign substance there may be in the atmosphere. For instance, in 
acid or alkali works, coal mines, copper mines, or other places of a similar char- 
acter where there is an unusual amount of dust or foreign substance in the 
atmosphere, which being drawn into the air passages of the machine, combines 
with the excessive amount of residuum or carbon left behind through oxydation, 
forming a substance for fire to feed on, the fire resulting from causes herein 
set forth. 

Our experience is, that the greatest amount of oxydation takes place at 
the point where the air passes from the cylinder into the discharge pipe. The 
result is that continued oxydation naturally decreases the size of the aperture at 
the mouth of the discharge pipe, and more air is compressed in the cylinder than 
can pass through the discharge pipe — the result being the re-compressing of the 
air, and an increased amount of friction, also an abnormal degree of heat in the 
air cylinder. The result from such cause is very apparent. 

As to the oil, it should have the least liability to oxydize that it is possible 
to secure. The flash point should be as high as good lubricating qualities will 
permit. What is the flash point? It is that degree of heat at which some con- 
stituent part of the oil passes off as vapor, which vapor being inflammable, will 
ignite if brought in contact with fire. 

The mere raising of the temperature of an oil to its flash point will not 
produce ignition. Another cause must be presented to produce ignition of the 
vapors. Indeed, such a cause may operate before the flash point is reached, as in 
the case of sawdust saturated with linseed oil. The cause referred to is, accord- 
ing to the writer's experiments, oxydation of the oil. 

Combustion, so far as we have to consider it, is in this case the rapid union 
of a substance with oxygen with the presence of a flame. There can be, of course, 
repeated oxydation without flame, but if the action be sufficiently repeated, heat 
enough will be generated to set the substance on fire. Then if a considerable 
quantity of inflammable vapor be present, an explosion is likely to follow. 

To furnish an oil which shall resist the relatively large quantity of highly 
heated oxygen (at a pressure of 45 lbs., three times as great on a given surface 
as at the pressure of the air), is a matter which requires special study and 
facilities. 

We have made a special study of the requirements of an oil which shall 
reduce the chances of the possibility of spontaneous combustion to a minimum, 



i6o 



PRODUCTION. 



and where such facts have been present, by the use of our material, a great deal 
of this serious difficulty has been avoided. 

Should any of your subscribers wish to correspond with us further regard- 
ing this matter, we would be very glad to do so. 

To sum up : Use an oil as little likely to spontaneous combustion as it is 
possible to secure it.. Have as few places where the oil can lodge in the machine 
as possible; in other words, have as few joints and as few turns in your pipes 
as it is possible to have, as it is a well known fact that where air strikes a surface 
in turning past a joint or elbow, friction is the result. 

It is also very necessary to avoid the free use of oil. Use just as little as 
possible. There is a strong tendency on the part of engineers to use too much 
oil, simply because they want to be sure of having enough — on the principle that 
it is better to have too much than too little. 

In Compressed Air we find another article bearing on this same subject, 
and the writer begs leave to say, that "to our minds, it is a very unsafe thing to 
attempt to cleanse a cylinder with soft soap and water, unless an abundance of 
water is used after the operation to cleanse the cylinder very thoroughly." 

Kerosene is still more dangerous; so the only safe method to pursue (to 
our minds) is to use oil as little liable to carbonize as possible, and to remove and 
clean the valves at short intervals. 

We feel that our experience in the manufacture of a suitable lubricant will 
at least justify the consumer in making a few experiments. Very truly yours, 

FISKE BROTHERS REFINING CO. 



Editor Compressed Air: 

Dear Sir — I am very much interested in the discussion now going on in 
your very instructive little magazine, Compressed Air, on the subjuct of explo- 
sions and fires in air compressing engines and air receivers. As I have had 
considerable experience in the handling of compressors, I give you my idea as to 
the cause of some of the explosions that occur in this type of machinery. 

Some ten years ago, during the construction of the New York Croton 
Aqueduct, I had charge of the machinery at Shaft No. i6. Section 8. We had a 
duplex air compressor at work with air cylinder i8" diameter x 30" stroke, and 
maintained a working air pressure of from 80 to go lbs. per square inch. The 
compressor was of the ordinary poppet valve type, and we had the usual trouble 
with this type of valve— that is, one or more of the valves would stick, due to 
the carbon deposited on them. The oil used was the best obtainable for this pur- 
pose, and was recommended by the manufacturers of the compressors. The air 
receiver (horizontal) was situated outside of the engine house and was exposed 
to the hot rays of the sun. On one occasion, in passing the receiver, I noticed 
that the rubber gasket between the flanges of the air discharge pipe and receivcr 
was on fire, and the pipe itself was red hot. I stopped the compressor soon as 
possible and took the manhole plate off receiver and found the inside on fire. 
We got out the fire hose and soon had the fire under control. After the receiver 
cooled off we made an examination to find out, if possible, what was the cause of 



r 



PRODUCTION. i6i 



the fire, and found the entire interior of the receiver encrusted with carbon at 
least ys" thick. In the meantime, while we were fighting the fire, several miners 
who had been running rock drills in the tunnel were knocked out by the fumes 
of the burning carbon and brought to the surface in an insensible condition. This 
l)eing our first experience of this kind, we were at first at a loss to account for the 
fire. We started to investigate, and were not long in discovering the cause. As 
stated in the foregoing, the air cylinders were provided with the ordinary poppet 
valves, and frequently several of them would stick, and when the engineer would 
notice that they did not work, would take a squirt-can filled with kerosene oil and 
squirt a quantity of the oil at the valves to cut the sticky substance ; the oil was 
immediately drawn into the cylinder, and being of a very low flash test, would 
quickly vaporize, and when the conditions were just right, would ignite and cause 
an explosion or fire. I have since noticed that this habit of using kerosene oil 
as above stated is quite a common practice with engineers who run poppet valve 
compressors. I have no doubt that this is the cause of many of the fires and 
explosions that take place in compressed air engines. Yours truly, 

PHILIP WEISS. 



Compressed Air: 

We have had some very peculiar experiences with our compressor during 
the past few days. The grease in the receiver just outside of the compressor 
caught fire, heating the receiver so hot that it melted the tar off the outside, and it 
heated the pipes going to the mine so hot that it melted the tar off for several 
feet from the receiver, and made the air so hot that the men had to quit cutting 
and leave the mine ; the men who saw it say the receiver was red hot. I have been 
told that compressors have been known to blow up, and I am going to put a spray 
of water on the compressor to keep it cool. 

We made a connection on to an air pipe from our electric plant, in our No. 
3 section with the return current ; making the connection at the pit mouth of No. 
3 section, and took it off a few feet away from where the pipe goes into the 
I'feceiver. That is to say, we tapped the discharge pipe that goes to No. 3 section, 
about four or five feet from the receiver, and put on a ground connection from 
our electric plant. Have you any idea that this had anything to do with setting 
the grease on fire? If you are not fully satisfied in your own mind, I wish you 
would take it up with some electricians, and ask if it is possible for such a thing 
to happen. Yours truly, Engineer. 



The best way to prevent the accumulation of grease in the pipes ant! 
receiver is to use an oil suitable for the work. This you very evidently have not 
been doing, but since you would not use that kind of oil, you ought to remove 
the manhead and give the receiver a thorough cleaning on the inside occasionally. 
That is what the manhead is for. 

Our diagnosis of the case is that you have been using an oil of such char- 
acter that it has deposited around the discharge valves, the discharge valve ports, 
and possibly in the pipe between the compressor and receiver a c^ke like sub- 



i62 PRODUCTION. 

stance which has reduced the area of the passages. Running your compressor, 
say 120 revolutions per minute, you have filled and emptied that cylinder 240 times 
per minute or four times per second. One-fourth of a second is a pretty short 
time for air to get out of the cylinder — just try to imagine how short a space 
of time that is — and especially when the ports have become obstructed and 
reduced in area from the deposits is consequent upon the use of an improper oil. 
Compressing air to 90 pounds pressure, the natural temperature, without 
cooling effect would be 430 to 450 degrees, but if your discharge ports were ob- 
structed, the pressure in the air cylinder might easily be a great deal more than 
90 pounds. This excess pressure, combined with the friction of the air through 
the restricted ports might produce a high enough pressure to volatilize or vapor- 
ize the oil to an explosive gas. This might set fire to the gum or grease in the 
discharge pipe or receiver, and result in exactly the condition of affairs which you 
describe. Under normal conditions we have never known this to occur, but when 
the air compressor is drawing its air in from the hot engine room is running too 
fast and under the conditions which your machine has been running under, it 
could happen. The thing for you to do is to put in another air compressor along- 
side of the one you have, running the two together at a moderate speed, use an oil 
better suited to the work, and if the ports are in any way obstructed, have them 
thoroughly cleaned out. The pipe leading from the receiver to the compressor 
should be disconnected and examined carefully. Some compressor engineers 
keep their discharge valves and passages clean and avoid firing by feeding soap 
suds through the oil cup into the air cjdinder. Use common soft soap and say 
every week run for two or three hours or half a day on soap suds instead of oil, 
letting the suds feed into the cylinder just as though you were feeding the oil, 
only let in a little more of it. The difficulty with most engineers is that they feed 
too much oil into the air cylinder. Oiling an air cylinder is not like oiling a steam 
cylinder : in the latter case the steam cuts away the oil, while with air a little good 
oil goes a great ways. 

A spray of water in the cylinder of an air compressor certainly keeps the 
temperature down and adds to the economy of compression, but the objections to 
water in an air cylinder are so great that we cannot advise you to use it. This 
used to be common practice years ago, but it has been abandoned except for 
special cases. You cannot lubricate a wet cylinder and you would have trouble 
with the parts cutting each other and getting leaky. If you use water enough to 
do any good, you will have to reduce the speed of the machine materially. 

We note that you have got a portion of the pipe line rigged up as a part of 
the electrical circuit. A six-inch pipe line gives a good deal of metal and under 
normal conditions the return of such a current through the pipe line ought not to 
do any harm. We should, however, expect electrolysis effect in time, possibly 
resulting in the complete destruction of the pipe line. Under certain conditions 
of grounded or short circuit currents, you might heat the pipe line up to a point 
where any greasy coating would be ignited and it is possible that in this case 
your electric current was the last straw that set the thing off. An explosion is 
not likely to occur right in the cylinder, but if it occurs in the receiver it is dan- 
gerous enough. — Ed. 



PRODUCTION. 



163 



AN AIR COMPRESSOR OF EXCEEDINGLY NOVEL DESIGN. 

An air compressor of exceedingly novel and original design has been prac- 
tically finished by the Chaquette Power Company of Bridgeport, Conn., in accord- 
ance with the plans of E. Chaquette, the inventor of the machine. 

The machine is calculated to develop 2,500 horse power in the shape of air 
under a pressure of 100 pounds to the square inch, which it is the intention of the 
company to distribute through mains for power purposes. The compressor is, 
essentially, an immense horizontal wheel composed of ten spokes or arms, each 
formed of two latticed girders connected by suitable bracing. The girders form- 
ing each spoke diverge from the centre or hub toward the periphery, and they are 
united at their outer ends by an encircling system of latticed girders. The general 




FIG. 43. 



arrangement of the wheel thus formed will be understood from the approximately 
correct plan view. Fig. 43. 

Journaled in the outer end of each spoke is a set of three solid wheels which 
are 9 feet in diameter and each of which weighs about 4^ tons. The centre wheel 
of each set of three travels upon a circular track, as indicated in Figs. 43 and 44. 
The track is beveled after the manner of the ordinary bridge turn table track. 
The other two wheels, the inner and outer, of each set are the actual working 
wheels of the system, as they operate the air compressors placed around the cir- 
cular track, which is 82 feet in diameter. 

The centre of the wheel is supported upon a rivet provided with a ball bear- 
ing placed on a masonry foundation. The hub A, Fig. 44, is formed with a plat- 
form in which are placed two compound steam engines, each of 70 horse power. 
Each engine shaft carries a pinion wiiich engages with an internal gear on the 



[64 



PRODUCTION. 



shaft B, Fig. 44. These two shafts, B B, are diametrically opposite each other, 
and on the outer end of each is rigidly mounted the centre wheel of the sets D D. 
The great wheel is therefore driven by the engines, which are independent of each 
other through the shafts B B and centre wheels of the sets D D. 

Placed vertically in pairs around the outside of the track are 50 compound 
air compressors, as shown in Fig, 43. Arranged in the same way around 
the inside of the track are 50 similar air compressors. Each of the 100 
compressors has cylinders 12 and 16 inches in diameter and a common stroke of 
12 inches. Pivoted centrally above each pair of compressors, in a bracket secured 




to the wall of the track is a rocker, lever shaped, as shown in Fig. 43. Each end 
of each lever is connected by a link with the piston rod of a compressor. Each 
lever upon the outside of the track is so located as to be in the line of travel of all 
the outside wheels of all the sets of three. Each lever upon the inside of the track 
is placed in the path of the inside wheels. The rocker levers are so formed and 
arranged as to be struck by the wheels in their passage, and through the connect- 
ing links to operate the pistons of the air compressors. 

The air tank is in the centre. There is also a 20-inch collectings main, 
which extends around the inside of the track, and with which suitable pipe con- 
nections are made with each compressor. This main conveys the air to the tank, 
which is expected to carry a working pressure of 100 pounds to the square inch, 



PRODUCTION. 165 

tills pressure having been decided upon as it is the most available one for power 
distribution. 

The operation of the machine will be readily understood. If the wheel 
should make ten revolutions per minute, there will be 100 impulses or strokes of 
the air compressors at each revolution, and 10,000 for the ten revolutions it is 
expected to make in each minute. Knowing the capacity of each compressor, it 
therefore becomes a mere matter of calculation to ascertain the power developed 
and made available, as air under pressure, if the wheel could be run at ten turns 
per minute. Taking into consideration the actual power applied at the centre to 
turning the wheel, the multiplication expected is something tremendous. As 
stated by Mr. Chaquette to our representative, it is calculated that of the total 
power developed, only about 43/2 per cent, will be required for the actual turning 
or operation of the wheel, and that the remaining amount, or about 95^ per cent., 
will be available for commercial purposes. The momentum of the wheels carried 
at the ends of the arms or spokes, their great weight compared with the work they 
are expected to perform, and- the constantly increasing leverage of their action 
upon the several rocker levers, are depended upon for the successful operation of 
the machine. It may be added in conclusion, that the machine has been protected 
very completely by letters patent issued to Mr. Chaquette. — The Iron Age. 



A DIMINUTIVE AIR COMPRESSOR. 

An air compressor 12 inches high, 15 inches wide and 28 inches long, and 
actuated by electricity, is a real thing, and not a mere plaything or curiosity. It 
is in practical use and doing service on electric cars to control the brakes. It is 




FIG. 45. — A DIMINUTIVE AIR COMPRESSOR. 

installed under the ordinary car seat, and if it is run for thirty seconds it will 
compress enough air to stop the car half a dozen times. 

The Standard Air Brake Co. build these compressors in connection with 
their air brakes, and they are as complete as the full-grown compressor used for 
heavier work. 

While the compressor is now used in connection with air brakes exclusively, 
its field of usefulness could be enlarged to a very great extent. 



i66 



PRODUCTION. 



There are many places where compressed air would be used, were it avail- 
able, and this little compressor and others of its kind might be profitably em- 
ployed; such as in pneumatic dispatch tubes, in pottery work for spraying colors, 
operating small pumps and dental tools, and innumerable other purposes. 



THE TAYLOR HYDRAULIC AIR COMPRESSOR. 

The compressor shown herein was installed for the Dominion Cotton Mills 
Co., Limited, to furnish power for their print works at Magog, Quebec. 

The installation of the machine was attended with much prejudice. The 
success attained by this plant has, however, convinced all those who doubted 




FIG. 46.— THE TAYLOR HYDRAULIC AIR COMPRESSOR. 

the feasibility of the invention. According to tests made on the 7th and 13th 
of August, 1896, by Prof. C. H. McLeod, Ma. E., of McGill University, this 
compressor gives 62 per cent, of the actual power of the water used, and de- 
livers over 15s H. p. in compressed air. This efficiency is secured in spite of the 
fact that 20 per cent, of the air is lost because of inefficient separation. 

The inventor will undertake in all subsequent installations to obtain an 
efficiency of at least 75 per cent. 



PRODUCTION. 



167 



The air was first used in the engines on the 12th of August, 1896, and since 
that date it has provided power continuously for seven printing machines, each 




Fu;. -1, 



i68 PRODUCTION. 

of which is driven by a pair of engines with 8 in. x 12 in. cylinders. It also fur- 
nishes power at night for the feed pumps of the boilers, the machine shop, and 
other purposes. The air pressure uniform at all times, whether supplying one 
or more engines, is 52 lbs. per sq. inch. The compressor requires no attention 
other than starting and stopping it. 

DESCRIPTION OF THE HYDRAULIC AIR COMPRESSOR. 

The annexed perspective drawing shows a complete compressor, its details 
being as follows: 

A. Penstock, or water supply pipe. 

B. Receiving tank for water. . 

C. Compressing pipe. 

D. Air chamber and separating tank. 

E. Shaft, or well, for return water. (The required pressure is propor- 
tional to the depth of the water in this shaft.) 

F. Tailrace for discharge water. 

G. Timbering to support earth. 
H. Blow-off pipe. 

I, Compressed air main. 

J. Head piece, consisting of — 

a. Telescoping pipe, with '■ 

b. Bell-mouth casting opening upwards. 

c. Cylindrical and conoidal casting. 

d. Vertical air supply pipes. (Each pipe has at its lower end a num- 
ber of smaller air inlet pipes branching from it towards the center of the com- 
pressing pipe.) 

e. Adjusting screws for varying the area of water inlet. 

f. Hand-wheel and screw for raising the whole head piece. 
K. Disperser. 

L. Apron. 

M. Pipes to allow of the escape of air from beneath apron and disperser. 
N. Legs by which the separating tank is raised above the bottom of the 
shaft to allow of egress of water. 

P. Automatic regulating valve. 

WORKING OF THE COMPRESSOR. 

The water is conveyed to the tank B through the penstock A, where it 
rises to the same level as the source of supply. In order to start the com- 
pressor the head piece J must be lowered by means of the hand-wheel f so that 
the water may be admitted between the two castings b and c. The supply of 
water to the compressor, and consequently the quantity of compressed air ob- 
tained, is governed by the depth to which the head piece is lowered into the 
water. The water enters the compressing pipe between the two castings b and c, 
passing among, and in the same direction as, the small air inlet pipes. A partial 
vacuum is created by the water at the ends of these small pipes, and hence 
atmospheric pressure drives the air into the water in innumerable small bub- 
bles, which are carried by the water down the compressing pipe C. During their 
downward course with the water the bubbles are compressed, the final pressure 
being proportional to the column of return water sustained in the shaft E and 



PRODUCTION. 



169 



tailrace F. The accompanying diagram shows the relative sizes of the bubbles 
as they descend in a compressing pipe 116 feet in length. 

When they reach the disperser K, their direction of motion is changed, 
along with that of the water, from the vertical to the horizontal. The disperser 
directs the mixed water and air towards the circumference of the separating 
tank D. Its direction is again changed towards the center by the apron L. From 
thence the water flows outward, and, free of air, passes under the lower edge of 
the separating tank. During this process of travel in the separating tank, which 
is slow compared with the motion in the compressing pipe C, the air by its buoy- 
ancy has been rising through the water and pipes M, M, from under the apron 
and disperser, to the top of the air chamber D, where it displaces the water. The 




FIG. 48.' — GRINDING ROOM. 

air in the chamber is kept under a nearly uniform pressure by the weight of the 
return water in the shaft and tailrace. 

The air is conveyed through the main I, up to the shaft to the automatic 
regulating valve, and from thence to the engines, etc. The air pressure in the 
main and air chamber increases i lb. per sq. inch for each 2 ft. 3J/2 in. that the 
water is displaced downwards in the air chamber by the accumulating air. The 
variation in pressure from this source will not be more than 3 lbs. per sq. inch 
in a working plant. As the automatic valve requires a change of only i lb. per 
sq. inch pressure to close it completely, it will be evident that, by properly ad- 
justing the valve, some air can always be retained in the air chamber, and that 
the water can be prevented from ever reaching the inlet to the air main. If a 



I70 PRODUCTION. 

large quantity of air has accumulated in the chamber, the valve allows of its free 
passage along the main; but when the air is being used more quickly than it is 
accumulating, and the pressure decreases below a certain point because the cham- 
ber is nearly emptied of air, the valve shuts partially, or completely, adjusting 
itself to the supply from the compressor. 

When the air has displaced the water almost to the lower end of the 
compressing pipe, it escapes through the blow-off pipe H. 



THE HARTFORD AIR COMPRESSOR. 

Some years ago recognizing the demand for an hydraulic air compressor 
that would do quick economical work without getting out of order easily, the 
L. E. Rhodes' Co., of Hartford, Conn., began a series of experiments to devise 
something more simple and efficient than the pumps on the market. A pump 
of the double acting form was finally adopted, the designers believing that that 
class of compressor would do much quicker and more efficient work than either 
the single acting pumps with their wasteful springs or weights and their inter- 




FIG. 49. — HARTFORD AIR COMPRESSOR. 

mittent action, or the clumsy "tank" styles with their waste air space to consume 
power and their various floats and valves. The aim in the first place was to 
secure simplicity and next to prevent waste of water or air. How successful 
they have been in combining the advantages of the old pumps and eliminating 
their defects is realized when it is seen that in the Hartford Air Compressor 
there are less than half the parts usually necessarj'- and no valve packings. The 
valve is a marvel of simplicity and efficienc)', and the entire force of the water 
is utilized for there are no narrow ways to choke and cause friction, with no 
weights to work against nor auxiliary cylinders and waste air spaces to con- 
sume power. So it is claimed for this pump, that it will keep up the desired 
air pressure with less water than any other on the market. But the most note- 
worthy improvement to guard against waste is the system of regulating. The 
L. E. Rhodes Co. maintain that loss of speed must be the result where the ordir 
nary practice is pursued of regulating down the pressure of the water (before it 
enters the compressor) to the desired air pressure and moreover that there is a 
great chance of leakage if the water is constantly bearing on the machine, 
whether air is being drawn or not. Consequently they have adopted a device 
whereby the water is shut off entirely when no air is being used. As air is 



PRODUCTION. 171 

drawn the regulator automatically opens and allows the maximum water pres- 
sure to bear on the pistons, insuring such a quick action that the desired air 
pressure is immediately regained, which in turn causes the regulator to close. 
The benefit of the maximum water pressure is thus obtained to drive the pistons 
rapidly, and constant strain on the pump is avoided with its consequent leakage, 
for when the pump is not working the water is shut off as if by a faucet. The 
regulator is simple and easily adjusted. 

Long practical use has now substantiated the claims of the maufacturers 
that the Hartford Air Compressor gives a maximum co-service at a minimum 
cost for water and repairs. All the force of water is utilized, insuring speed and 
very high efficiency, and there is no annoyance waiting for a tank or cylinder to 
empty and no waste of water through leakage. Extremely simple in design ; with 
the troublesome springs and valve packings done away with ; high grade in con- 
struction, with a quick easy action and positive regulation, the Hartford Air 
Compressor truly seems an advance over anything yet devised. 



HYDRAULIC COMPRESSION OF AIR. 

At a recent meeting of the Manchester (England) Association of Engineers, 
Mr. H. D. Pearsall, of London, read a paper on "Hydraulic Plant for Compressing 
Air." Restricting the terms of his address to cases where water was the main 
agent — i. e., cases of the application of water power to the compression of air — 
he described various processes, the loss of energy in the application of which, he 
pointed out, had set back the development of that class of machine. Believing the 
principle to be right, he gave some consideration to the subject, and arrived at the 
conclusion that the imperfections were solely questions of design capable of recti- 
fication, and that the losses of power which were unavoidable were very small. 
He explained, by a series of drawings, an engine erected on the river Kent in 
Westmoreland, from designs he had prepared, the efficiency of which amounted 
to 80 per cent. — that was, that the work done measured in isothermic compression 
of air was 80 per cent, of the gross power of the water. When they compared 
that with the 30 per cent, or 35 per cent., — and not that always, — which was com- 
monly attained in piston compressors driven by water wheels, it must be admitted 
that the question of the use of compressed air assumed a totally new aspect. In 
a great variety of cases where with a low efficiency it was not worth while to use 
compressed air, or where electrical transmission, for instance, might be obviously 
preferable to transmission by compressed air, the case was entirely reversed it 
an)rthing lik an efficiency of 80 per cent, could be attained, and attained in 
machines of simpler and less costly description than that which they superseded. 
Experience with the engine had revealed still further possibilities of improvement. 
Finality had not been reached, and he did not say that an efficiency of 80 per cent, 
could be bettered, but in other directions, such as making an engine of the same 
size do more work, the engine would be improved on in subsequent engines. 
Other developments of the same principle had also been suggested by it which 
were not yet carried out in practice. — American Manufacturer. 



172 



PRODUCTION. 



WAVE AIR COMPRESvSOR. 

Mr. R. Toennes, of Boonville, Mo., is the inventor of what he calls a 
"Wave Air Compressor." The power of the waves is utilized for the purpose of 
compressing air in a manner quite novel. 

Briefly described the invention is as follows : 

A shaft or tower, as shown in the larger figure, is constructed on or near the 
shore of a body of water where there are waves, or a tide. This tower is com- 
posed of one or more air-tight chambers (4), as circumstances may demand, and 
may be constructed of any substantial material. 

The tower is built upon a solid foundation of rock. At its base (2) is an 
opening, with divergent top and side walls. Through this the waves enter the air 




FIG. 50. — WAVE AIR COMPRESSOR. 



chamber (4). This chamber is provided with a valve (6). The force of the 
wave opens this valve and admits the air to the compressing chamber (4). In this 
chamber is another opening, covered by a ball of some substance of a less specific 
gravity than water, kept in position by four vertical rods of metal, brought 
together at the top. As the waves recede, the valve (7) admits air from the out- 
side, thus, by atmospheric pressure, forcing the water out of the chamber. The 
ball, floating upon the water, closes the opening as soon as the water has escaped. 
The air which was compressed by the action of the wave is admitted to the storage 
chamber by a valve (6). With each subsequent action of the water more com- 
pressed air is admitted to this storage chamber, thus in a short time affording a 



PRODUCTION. 173 

reserve force. This is utilized by means of a pipe, provided with a stop-cock (14), 
by means of which the concentrated power may be transmitted to the point at 
which it is desired to be used. The numerals (5) represent the horizontal parti- 
tions between the chambers; 12 represents the bottom, and 13 the top of the tower. 

The smaller figure represents a horizontal section of one of the chambers, 
showing the manner in which the water valveand the ball (8) operate; 2 is the 
opening and 3 the outwardly inclined side walls for the admission of the waves. 

This principle has never before been used in obtaining compressed air. 
Aside from the cost of construction, it requires but little outlay, and at the same 
•time is capable of doing good work. It may be used on any body of water where 
the waves are of sufficient force. On the seashore the desired result may be 
obtained, where the coast is favorable, by constructing the shaft on the shore, or 
in the cliffs, and permitting the waves to enter by means of a tunnel, thus obtain- 
ing the advantage of cheapness of construction and stability. The tower may con- 
sist of one or more chambers, the number and height depending entirely upon the 
tide and waves. 



HYDRAULIC PLANT FOR COMPRESSING AIR.* 

The term "hydraulic plant for compressing air" may, of course, include all 
machinery for compressing air in which water takes any part. It should, how- 
ever, certainly be restricted to the cases where water is the main agent — i. e., to 
cases of the application of water power to the compression of air, and that is the 
sense in which the term is here used. The most usual way of applying water 
power to this purpose is to cause the water to produce rotary motion in some sort 
of a wheel, and by means of this rotary motion to drive reciprocating pumps in 
which air is received and compressed. This is obviously rather a roundabout 
process, involving the use of two distinct machines besides gear connecting them, 
and several conversions of energy. It is, of course, well known that though 
energy is indestructible it cannot be changed from one form to another without 
loss, and consequently, if there are several transformations of energy, there must 
be several losses. In converting the potential energy of water descending from 
a height into the rotary energy of a turbine, from 20 to 25 per cent, is usually lost. 
In the gear required to connect the wheel to the pumps there is also lost a per- 
centage of the energy of the wheel, and in converting this energy to that of the 
reciprocating pistons, a third loss is suffered. The loss due to intermediate gear 
is frequently very considerable, because a turbine necessarily runs at a high speed 
and the pumps must run at a low speed. The consequence is that the net energy 
received by the pump piston is seldom more than half that of the original energy 
of the water, and is often much less. If, therefore the power of the water could 
be applied more directly, we should expect to attain a great economy of power; 
consequently, many efforts have been made to secure this object. Obviously, these 
considerations apply to the use of water power for any kind of pumping — c. g., 
pumping water, as well as compressing (1. e., pumping air) — but in the case of air- 

* Paper read by Mr. II. D. Pcarsall, M. Inst. C, E. of London, before Manchester .Asso- 
ciation of Engineers. 



174 PRODUCTION. 

compression there is still another reason for desiring the direct application of the 
power. All the work done in compressing air is converted into heat, but when air 
io compressed under such conditions that all the heat is instantly and entirely 
absorbed by surrounding solid or liquid bodies, only about half as much net work 
is exerted (if, for example, compression is to one-fifth of original volume) as 
when no heat is thus absorbed. Therefore, it is obvious that it is of the highesf 
importance to thus absorb heat during compression of air. In compressing air 
in reciprocating pumps, it is found practically impossible to absorb more than half 
the heat which is developed, and this is not surprising when we find that the 
greatest quantity of water which can practically be used, under the circumstances, 
for cooling is about two-thirds the weight of the air compressed, while the quan- 
tity of heat to be removed is very large indeed, amounting to fifty-eight heat 
units per pound of air when compressed to five atmospheres. But the quantity 
of water actually available when the motive power is water is never less than 1,000 
times the weight of the air. Hence the strongest reason for applying the water 
used for power directly to the air — that if it can be done it should result in very 
much more thorough absorption of heat than can be accomplished in any other 
way. This analysis of the imperfection of air-compressing machinery is, of 
course, modern, but the practical result — that the inefficiency was very great — has 
been realized in a rough way ever since compressed air has been in common use, 
and, therefore, the attempts to apply the water directly have been many. 

In this paper the author intends to confine his attention to those hydraulic 
air compressors which more or less perfectly attain this object. They may be 
divided into two classes: — In that which will be mentioned first the compression 
is effected by the weight of a column of water of a height equal to the maximum 
pressure of the air measured in feet of water. To obtain this pressure the water 
used as power is carried down a well or shaft and up again in an inverted siphon. 
The air to be compressed is diffused through the water in bubbles as small as pos- 
sible, and part of it is then carried down to the bottom of the well by the stream. 
That which arrives there is, of course, then subject to the pressure of the water 
column above it and is accordingly compressed, and means are provided for allow- 
ing it then to escape from the water before it can again expand. This method is 
one of the very oldest known. One form of it is described by Pliny in the first 
century, and even then was old. In modern times several different inventors 
have revived it, and it is connected with the names of Upham, Mowbray, Frizell 
and C. H. Taylor. In this machine, as might be expected, the compression is 
isothermal, and it is a very simple machine and has few working parts. It is, 
however, rather an expensive one, as for a pressure of five atmospheres it requires 
the sinking of a shaft 150 ft. or more in depth, with an enlarged chamber and 
some of the apparatus at the bottom of the shaft. Moreover, when its principles 
are examined, it is found that the unavoidable losses connected with it are large, 
so that its theoretic efficiency is not very high. These may be chiefly embraced 
under the head of fluid friction due to the flow through a pipe 300 feet long and to 
eddies. The fluid friction is not merely that of water flowing through a pipe. 
The bubbles of air, although they descend with the water do not descend as fast 
as the water. Consequently the water is all the time passing the bubbles, and the 



PRODUCTION. 175 

rubbing surface causing fluid friction is, therefore, the whole surface of innumer- 
able bubbles of air, in addition to the surfaces of the pipe. The co-efficient of 
friction is, therefore, very much greater than that of water in a pipe. The effi- 
ciency actually realized in practice appears to have been about 55 per cent, under 
the condition of using a very large pipe, a low fall and a pressure of only four 
atmospheres. Both a higher fall and a higher pressure diminish the possible 
efficiency. 

In the other class of machines having the same object water acts as a pis- 
ton, compressing the air in a chamber provided for the purpose. The earliest is 
probably due to Montgolfier, the inventor of gas baloons and of the hydraulic 
ram, about one hundred years ago, who described and patented a modification of 
his hydraulic ram to be used for the compression of air. It was quite a practicable 
machine, though possessing some complications which have been proved to be 
needless. But the reason why it has failed to come into use is the same reason 
which for so many years has confined the hydraulic ram for water raising to 
machinery of small and almost domestic size, viz., the construction of the main 
valve. In Montgolfier's machine the escape valve was similar to that of the Mont- 
golfier water ram, and it was operated as that is, by the current of the escaping 
water. This necessarily limits these machines to a very small size, and, as when 
compressed air is wanted, it is nearly always wanted in considerable quantity, this 
alone would naturally prevent any use being found for these machines. That 
this construction was unsuitable for any large size one supposes should have been 
obvious ; but, as for one hundred years, in nearly all attempts to improve the ram 
they insisted on retaining it, it seems it was not obvious. It was, however, 
abandoned in the next application of this principle which will be mentioned. 
This is the air compressor designed and used by Sommeiller in the excavation of 
the Mount Cenis tunnel. It consists of a pipe leading from the source of supply, 
two valves, a vertical pipe in which air is compressed, and a valve controlling the 
connection between this compression chamber and an air-vessel. The water does 
not act merely by its pressure. When it begins to flow, the air in the pipe offers 
very little opposition to it, and therefore the water acquires a high velocity and 
momentum. As the air becomes compressed it offers more and more resistance 
to the water, and this resistance absorbs the momentum of the column of the 
water. The compression is effected, therefore, more by the momentum of the 
column of water, than by its pressure. Hence it is essentially an hydraulic ram. 
The head of water was 85 ft., and the air was compressed to 6 atmospheres. Not- 
withstanding numerous defects of designs, these machines had considerable suc- 
cess. Ten of them were made, and after they had been in use three years at the 
Bardonneche end of the tunnel, six others were made for the Modane end of the 
tunnel, where the fall was only 35 feet. In this latter installation a most remark 
able course was adopted, the history of which is very instructive. The natural 
fall being only 35 feet, the water was first pumped by water-wheels to a reservoir 
at a height of 85 feet, and then used with this fall in the compressors. But a 
little consideration shows that this was entirely needless. If, instead of doing 
this, the valves had been worked in a different way, a fall of 35 feet would have 
compressed the air just as well as a fall of 85 feet. The mean pressure due to 
compression to 6 atmospheres equals 61 feet of water. When the fall was 85 feet 



176 PRODUCTION. 

the water would give a mean pressure throughout the height of air column of 85 
feet, less the loss of effect from fluid friction, etc. Hence if the efficiency was 75 
per cent., the flow of the water would be adequate to compress all the air above 
the level. The gross energy developed would evidently be represented by 85 
feet X height of air column. Now with a fall or head of 35 feet, suppose that after 
the chamber was emptied of water through the second valve, instead of then 
closing it before opening the first valve, the latter had been opened while the 
second still remained open. Water would then have flowed away through the 
second valve, and when the column had acquired a certain velocity the valve 
would be shut, and the compressing stroke would then take place. The energy 
available for compression would then be represented by length of column of water 
in pipe x head due to velocity + 35 feet X height of air column, and it is evident 
that by making the velocity a certain amount — that is, by keeping the second valve 
open a certain time — the amount of this energy can be made exactly as great (or 
greater if desired) than the energy that was developed under 85 feet head. In 
1891, the author described in a paper in the Proceedings of the Institution of 
Civil Engineers an engine of considerable size for pumping water on the 
principle of the hydraulic ram, and then mentioned that he had also made experi 
ments in compressing the air in the same manner. One of these engines has since 
been erected on the River Kent, in Westmoreland, from the author's design. This 
also consists of a pipe from the source of supply, and a chamber in which the air 
is compressed by the momentum of the water. But in this engine the method 
of using the water is that which the author suggested should have been used at 
Modane. The water runs freely away through the valve for a certain time in 
order that it may acquire a certain velocity and momentum. The valve is then 
closed and the energy available for compression is exactly as the author already 
formulated it. Consequently, such an engine may be used on a fall, however 
small. In this engine there is only one valve in place of Sommeiller's two. The 
air valve admits a fresh supply of air into the receiver after the compression is 
accomplished, and also allows of the escape of some of this air while the main 
valve is closing, so that part of the water which flows in the main pipe during 
this time can rise freely in the chamber instead of having to find an exit through 
the narrowing orifice of the main valve. The valve is closed by the water when 
it reaches a float attached to a lever in connection with the valve. There being 
but one water valve, there is but little gear required to operate it, but it is neces- 
sary that the valve should open and shut at certain definite intervals of time. 
The author has used several different forms of gear for this purpose. In the 
earlier engines it was a cam, in the Kent engine it is a crank motion. In all cases 
the power to operate the gear is taken from the air vessel. In the Kent engine 
water is used. In other cases an air motor has been used. In the Sommeiller 
engine it was only possible to make three strokes per minute, probably on account 
of the imperfection of the way of operating the large valves, and because appar- 
ently certain pauses were necessary between each stroke. In this engine, there 
are, of course, no pauses, and from fifteen to twenty strokes are made per minute, 
so that an engine of given size will develop a much greater power. The height 
of the chamber is also reduced one-half by making its diameter half as large 
again as that of the main pipe. The working of this engine has fully justified the 



PRODUCTION. 177 

author's expectations. In the compression of the air practically all the heat 
developed is absorbed as it is developed — as, indeed, it seems obviously must be 
the case, for the compression is effected in a chamber which is cooled at every 
stroke by being filled with a mass of cold water, and therefore, in the midst of a 
mass of cold wet cast iron on sides and top and of cold water below. The ribs of 
the valve plate further add to the mass of cold iron and to its surface. A register- 
ing thermometer was suspended in the air vessel, and after several hours running 
the highest temperature shown was about 2 deg. above that of the water. The 
engine runs with perfect smoothness and regularity without any noise (even as 
nuich as that of the ordinary pumps) or concussions of any kind. It is essen- 
tially an hydraulic ram, and the popular idea of a ram appears to be that the es- 
sence of its action consists in a blow. This idea has, of course, no scientific 
foundation, but practice is perhaps more convincing than theory, and the fact is 
very practically demonstrated here. It will be obvious that air is here com- 
pressed without any intermediate transformation of power, and therefore the 
three sources of loss of power referred to in the beginning of this paper are 
reduced to one. The other unavoidable sources of loss are also small. The fluid 
friction is merely that in a plain pipe of no considerable length and the moving 
parts are very few and such movement is slow. The efliciency, therefore, is, as a 
necessary consequence, very high, amounting to 80 per c;^nt. That is, the work 
done measured in isothermic compression of air is 80 per cent, of the gross power 
of the water. 

In a great variety of cases, where with a low efficiency it is not worth while 
to use compressed air, or where electrical transmission, for instance, may be 
obviously preferable to transmission by compressed air, the case is entirely 
reversed if anything like an efficiency of 80 per cent, can be attained and attained 
in machines of simpler and less costly description than that which they super- 
sede. Experience with this engine has revealed still further possibilities of im- 
provement. Finality has not been reached, and the author does not say that an 
efficiency of 80 per cent, can be bettered but in other directions, such as making 
an engine of the same size do more work, this engine will be improved on in sub- 
sequent engines, and other developments of the same principle have also been 
suggested by it which are not yet carried out in practice. 

In the discussion following the reading of the paper, 

Mr. W. J. Jenkins said the great drawback in connection with the compres- 
sion of air by direct water-power was that which caused the compressors at the 
Mount Cenis tunnel to be thrown out — the very large expense in laying down 
plant, and the very small output obtainable from it. The total cost of two of the 
machines at Mount Cenis was £7,000, and the amount of air turned out about 8,000 
cubic feet per hour in each, or an expenditure of £3,500 for 8,000 cubic feet turned 
out. That amount of air could be very well compressed by a steam engine costing 
not more than £400. JIc would like to know how Mr. Pearsall measured the 
amoiuit of compressed air delivered, because on that point the question of effi- 
ciency depended. He had never been able to convince himself that any system will 
measure compressed air properly, except by pumping it into the receiver at a cer- 
tain pressure. The great drawback to any hydraulic system of direct compression 
would, of course, be the immense weight of the water that must be dealt with. No 



178 PRODUCTION. 

doubt in the colonies and other places where large water-power was obtainable, 
the author's apparatus would meet with considerable success. 

Mr. Constantine said he knew a case where there was a large compressing 
plant used for mine purposes, for driving rock-drills and hydraulic motors, and 
the engineer was often called to account by the mining captain for not keeping 
up the supply of compressed air, although the engineer held that his plant was 
working satisfactorily. What was wanted then, was some apparatus which could 
be fitted to the outflow pipe leading down the mine, to register, even if only 
approximately, the quantity of air which had passed from the compressor to the 
mine. Was there any apparatus for such a purpose? 

Mr. Alfred Saxon asked the author in what direction was it likely that his 
apparatus for compressing air would be used — in places where there was the 
necessary water power — instead of the other forms of power application that were 
available, such as electricity, steam engines, and other kinds of motive power. 

Mr. Pearsall, in replying, said the Sommeiller machine at Mount Cenis 
only made three strokes per minute, and the reason why there was so little work 
done was that between each stroke it had to make a long pause. In measuring 
the air he had often pumped it into a spare air-vessel in a simple way which gave 
the exact quantity of air compressed. Perhaps the best way was to fill a second 
air-vessel with water, and at a given instant turn the air into it, and open a tap at 
the bottom so that the air coming in drove the water out; the pressure in the 
second air-vessel was thus kept constant, and the measure of the air pumped in 
was simply the measure of the water that came out. In the case mentioned by Mr. 
Constantine, of course if they could conveniently establish a receiver for measur- 
ing the air, it was the very best plan, but this might be a little troublesome, and in 
such a case it might be better to be able to ascertain at any moment how much 
air was passing. He did not see why they should not put a little meter on the pipe 
which would tell the quantity passing at any moment. Of course, the field for 
hydraulic plant was much greater in countries where they had larger water power 
than in England. With regard to compressed air compared with electricity, his 
idea was that in a great number of cases, if the initial cost of compressing air, 
which had hitherto been so great, could be very largely reduced, the economy of 
transmitting power by compressed air would be greater than the economy of trans ■ 
mitting it by electricity. There were numerous incidental advantages in com- 
pressed air as compared with electricity. In mining, the advantages of com- 
pressed air hardly admitted of question. 



A GASOLINE AIR COMPRESSOR FOR BRIDGE WORK. 

The Illinois Central Railroad is at the present time engaged in an interest- 
ing piece of work in connection with the strengthening of its bridge at West 
Point, Ky. The chief interest attaches to the manner in which the conditions of 
shop work are made practicable upon a bridge already erected and under traffic 
by the use of a portable plant for generating compressed air for the operation of 



PRODUCTION. 



179 



riveting tools. The power is supplied by a 12-horse power gasoline engine fur- 
nished by Fairbanks, Morse & Co., and the tools operated are riveting hammers of 
the Chicago Pneumatic Tool Co. 

The bridge and the location of the plant upon it are shown by the accom- 
panying engravings from photographs. The operations in question are confined 
to the draw span, 265 feet in length, supported on a stone center pier at a height 




FIG. SI. — GASOLINE ENGINE AIR-COMPRESSING PLANT. 



of 65 feet from the water. The end abutments of the trestle work forming the 
approaches are supported by two steel caissons tied together at intervals. 

In the original construction the bridge had a wooden floor resting on the 
cl'ords. It was considered of insufficient strength for the traffic and it was de- 
cided to put on a new floor structure. This was accotnplisht'd by hanging cross 
girders from the pins of the bridge, upon which should rest two sets of stringers 
the latter being built up and riveted. The stringers are 28 inches deep and placed 
about 18 inches apart. The inner set of stringers carries the ties and supports 
the track. Double sets of braces were riveted to the crossbeams for connecting 
the Stringers, anxl also for attachinc: the lateral braces, and for this riveting. 



i8o 



PRODUCTION. 



requiring %-inch rivets and passing through two and three thicknesses of plates, 
some experimenting was necessary. 

It was found difficult to use the yoke riveter which would ordinarily have 
been put upon this kind of work, owing to the peculiar conditions of the structure. 
The space between the stringers was insufficient to admit the frame, and it became 
necessary to use the pneumatic hand hammer. Two kinds of hammers were fur- 
nished by the Chicago Pneumatic Tool Co., the numbers "o" and "ooo" Boyer. 
and good work has been accomplished. It was also impossible to use the pneu- 
matic rivet holder-on, and the hand "dolly" was substituted. 

The compressor plant is the direct-connected gasoline engine air compres- 
sor, which has been especially designed by Fairljanks, Morse & Co., for isolated 




FIG. =>2. — THE BOYER HAMMER DRIVING I-INCH RIVETS. 



and portable plants. It is located on one side of the track, being placed on two 
6'x i2-inch timbers bolted together and lagged fast to timbers placed across the 
stringers underneath the rails. The compressing plant is located at the middle 
of the span and air carried by means of a pipe. Openings are provided in the 
pipe at short intervals, and hose connections made for operating the riveting 
hammers at any required position. The engine itself transmits power directly 
from the engine piston to the air piston. The air cylinder is single acting, having 
one set of valves, and a mechanically operated unloading valve relieves the com^ 
pressor when the desired pressure has been reached. The engine is thus left under 
no load until the pressure has descended to a determined point, and under this 
condition the governor admits sufficient gasoline only to maintain speed. This 
feature has an important bearing on economy, since the fuel used is in direct prQ- 



'^^' 



PRODUCTION. 



iSi 



portion to the amount of work actually performed, and the automatic features 
reduce to a minimum the cost of attendance. In the present case the engine oper- 
ates continuously all day without attention. The lubrication is by sight feed cups. 
One of the engravings herewith shows the location of the compressor and 
also of the rivet-heating forges. These are run at present by hand blast, but it has 




FIG. 53. — GASOLINE AIR COMPRESSING PLANT FOR PUMPING. 



been suggested and planned to run a small jet of air to the forges for this pur- 
pose. The whole operation of setting a rivet consumes practically 15 seconds 
on an average. On account of the inaccessibility of some of the rivet holes the 



1 82 



PRODUCTION. 



time consumed is considerably more than 15 seconds. It is estimated, however, 
that one of the riveting machines is doing the work of three hand operators and 
the i2-horse power gasoline engine compressor is of suitable capacity to supply 
three or four riveters. 

The smaller of the two sizes of riveting hammers used was designed lor 
^-inch rivets, but it was found that it did effective work on those of J^-inch 
diameter. It was, however, a little slower in the work on these rivets, and the 
large size hammers with pistol grip were fitted with an additional handle for hold- 
ing in position. The work has thus been expedited by using two large hammers 
on the %-inch rivets, and working the smaller hammers on the ^-inch rivets 
on the upper structure of the bridge, which is being changed from lattice bracing 
to plate for giving additional strength. 

The foreman and the entire gang engaged upon the work were accustomed 
to hand riveting only, and it was somewhat difficult to convince them that the 




FIG. 54. — THE BOYER HAMMER ON BRIDGE RIVETING. 



work could be done by air. Later the foreman expressed himself highly in favor 
of the pneumatic machines. It is stated also that the pneumatic tool is superior, 
especially for reaching down between the deep stringers, as in the case of hand 
riveting it would be necessary to use a riveting bar about 3^ feet in length, and it 
io almost impossible to keep the bar from jumping from the rivet at every stroke 
of the hammer. In this way time is lost and poor work the result. 

The large hammer referred to as furnished by the Chicago Pneumatic Tool 
Co. is an entirely new device, recently designed by them for heavy work. It is 
constructed on the same principle as the lighter forms of the Boyer hammer, but 
has a capacity up to i inch, and has been used upon ij^-inch rivets. A hook bar 
is used for holding up rivets, and its speed is such that rivets can be driven faster 
than they can be made ready and put in place. Six to seven seconds are said to 
be ordinarily sufficient for driving a rivet. It has been designed especially for 



*?:^ -f-' 



PRODUCTION. 



183 



heading down staybolts, placing truck rivets, pipe riveting, etc. The Risdon Iron 
Works of San Francisco report in regard to the work of this tool on pipe riveting 
that they have driven 200 ij^2-inch rivets per hour at a cost of one-fifth that of do- 
ing the same work by hand. The tool is illustrated in one of the accompanying 
engravings, driving i^A-inch rivets. While known as the large hammer, the term 
has relation to capacity rather than weight, the latter being 10^2 pounds. 

The gasoline air-compressing plant in use upon this bridge is in extensive 
use in mining work for operating rock drills, and in irrigating. The illustration 
shown on page 181 is of a plant installed by Fairbanks, Morse & Co. at Gardena, 
Cal., where a 12-horse power gasoline engine air compressor discharges 700 gal- 
lons of water per minute from a 7-inch bored well, with a total head of 29 feet. 
The air pressure is 45 pounds and the cost of running the plant ten hours is given 
as $1.35, using distillate at ten cents per gallon. The principal advantage, aside 
from that of economy in operation, claimed for the plant, is the fact that the 
machinery is entirely above ground and accessible. The adaptability of the same 
plant for the operation of pneumatic tools on bridge work may be considered 
as an important advance, affording in the field the facilities which have hitherto 
been available only in the shop. — Railway Age. 



BELT-DRIVEN AIR COMPRESSOR FOR SHOP SERVICE. 

The half-tone and accompanying drawings illustrate an air compressor 
especially designed for the constant maintenance of a working supply of com- 




FIG. 55. — BELT-DRIVEN COMPRESSOR. 

pressed air in machine shops, boiler shops, foundries and similar places where it 
is the growing practice to employ air-operated tools and facilities. The com- 
pressor is of the belt-driven type, with tight and loose pulleys, for easy stopping 



1 84 



PRODUCTION. 



and starting. It is designed to be usually kept constantly running, a pressure 
governor automatically operating a run-around which stops the operation of com- 
pression when the pressure rises above a given point, and allows it to resume 
again when the pressure falls. One of the special features of this machine is that 
the governing action does not stop the flywheel, which is always ready to respond 




FlC. 50. — SIDE VIEW OF BELT-COMPRESSOR. 



to duty. The compression is in two stages, with an efficient intercooler between 
the cylinders. The diameter of the cylinders, each single acting, are respectively 
13 inches and 8 inches, with a stroke of 12 inches, and the free air capacity at 120 
revolutions per minute is 100 cubic feet of free air, the permissible pressure being 
no pounds gauge, although 75 or 80 pounds is the more common practice. The 
pulleys are 60 inches x 1034 inches, and the belt may be led off in any direction 
most convenient, the revolution being in either direction. 



PRODUCTION. 1S5 

The same style machine is also built in size 16 inches in diameter, 10 inches 
diameter, 16 inches stroke. Flywheel 66 inches diameter, 15 inches face, having 
a capacity at 120 revolutions of 200 cubic feet of free air per minute. As will be 
seen, the compressor is entirely inclosed, but the working parts are easily acces- 
sible. By the hinged door at each side the connecting rods, cranks and main 
bearings are reached; all the valves are in the cylinder heads, each valve having 
its own cap and being independently removable. In the half-tone the high-pres- 
sure cylinder is nearest the observer, and the air is discharged at the side flange, 
to which the pipe to the receiver or line is to be attached. The free air enters 
at the side flange of the other cylinder, and if for any reason desirable an air 
pipe from the outside of the building or elsewhere may be connected. The pro- 
vision for the lubrication of every working part is deserving of notice. There 
are chain oilers on the main journals and a pressure grease cup takes care of the 
upper pin. The base of the compressor is 6 feet x 3 feet and the total height is 7 
feet. The drawings give very clear information as to the construction and opera- 
tion of this compressor. 

The design of this compressor, is admirable, giving many points of advan- 
tage over other styles ; the single-acting cylinders give 80 per cent, more cooling 
surface than the ordinary single cylinder, double-acting, increasing the efficiency 
in proportion, and doing away with troublesome stuffing boxes. This immense 
cooling surface is thoroughly water-jacketed, and partitions so arranged that 
there is a forced circulation of cooling water, so that all parts subject to excessive 
heat are kept cool. The advantage gained is readily understood. 

This style of compressor is nearly double in weight of the same size of any 
other make. 

These machines are now being manufactured in both single and double 
stage, either belt or steam driven, of sizes from 25 to 200 cubic feet of free air per 
minute, by the Curtis & Company Manufacturing Company, St. Louis, Mo. 

We are also pleased to call attention to the very handsome catalogue which 
this concern has just issued, and it will be sent to all interested parties l)y apply- 
ing to the manufacturers. 



AUTOMATIC AIR PUMP. 



A pretty little air pump just large enough to set almost anywhere is manu- 
factured by the Auto-Electric Air Pump Co., 39 Cortlandt street. New York. 

It consists of a one-sixth horse power electric motor, which can be arranged 
to operate by no volt continuous current, alternating current or storage battery as 
desired and an air compressing cylinder three inches in diameter by three inches 
stroke. Both the motor and the cylinder are mounted on a square cast iron base 
as shown herewith. The whole apparatus occupies a space of ten inches square 
and is enclosed in a glass case. When power is applied the motor operates the 
pump, producing a volume of air of 2.25 cubic feet per minute at 100 revolutions, 
enough to do a certain work such as operating dentists' tools, physicians' 
atomizers, pumping ale, beer or mineral waters, pumping tires, operating clocks 
and providing power for innumerable small works. Photographers, monumental 
designers, lithographers, architects and mechanical draughtsmen, also those who 



i86 



PRODUCTION. 



color photographs, lithographs, etc., will greatly improve their work and save time 
and annoyance by the use of this air pump. An illustration is given in the cover 
showing its use for artists. With the use of the foot pump to furnish air for the 
air brush, it has always been a matter of wonder how an artist could operate a 
pump with his foot and do good work with his hand. The Auto-Electric Pump 
operates automatically. It needs no attention beyond starting and it then starts 
and stops itself, maintaining a constant pressure at a desired point. 

The use in which this apparatus finds its greatest utility is in pumping beer 
and other liquids in saloons, etc. It takes the place of carbonic acid gas and the 




FIG. 57. — ELECTRIC DRIVEN AIR PUMP FOR SMALL DUTIES. 



consumer is benefited by the change, as he gets only the natural effervescence 
instead of a highly charged gas in his beverages. The cost to the user is very 
much reduced and there is no refilling of reservoirs and consequent annoyance. 
Already numbers of saloons have adopted the air pump. One user says he draws 
from eight to ten barrels of beer and ale per day, and previous to running this 
pump his water bills for running the old style pump were from $18 to $24 per 
month. Since using this pump water bills run from $1 to $2 per month. To do 
the work mentioned the cost does not exceed 50 cents per month for electric cur- 
rent. The pump is capable of pumping from 20 to 30 barrels a day. 



PRODUCTION. 187 

THE GLEASON-PETERS PUMP. 

A variety of air pnmps that would come in exceedingly handy for experi- 
mental purposes and would answer where only a small quantity of air was needed 
are made by the Gleason-Peters Pump Company, Houston street, New York. The 




illustration shows an improved triple cylinder pump which can be operated by 
electric motor or from counter shaft. Requires but one-fifth h. p. at 75 revolu- 
tions and makes 150 lbs. pressure. 



Dec. 12, 1899. 
Editor Compressed Air: •- 

I have a 24 X 18 power exhauster which operates satisfactorily at 40 R. P. 
M. with a port opening 20 x 1% inches. 

With 27-inch vacuum at what speed could this machine be operated to 
advantage? This machine has a simple slide valve, no lap, with eccentric 90 
degrees ahead of crank. 

If we desired to make a 9-16-12 D4 steam driven exhauster, at what speed 
do you think it would operate? It seems to me to be a question of velocity of gas 
through a variable port opening. If you can give me any idea it would be appre- 
ciated. 

Thanking you for any information which you may give me, I am, 

E. W. King, M. E., 
Deane Steam Pump Co., Holyoke, Mass. 



The data given by Mr. King is somewhat limited, and it is possible that we 
have not obtained a proper understanding of his purposes. To begin with, the 
engine described is a practical steam engine with a slide valve which is rigidly 
connected with moving parts and has a definite cycle which insures a certain 
relation between the piston and the valve at all times. The action is the reverse 
of the ordinary steam engine, in that air is admitted in what is usually the exhaust 
and is discharged from the steam chest, which is always the inlet in the usual 
engine. We will assume the piston at one end of its stroke just starting back, and 
we will assume that air is taken in for a full stroke on one side, and discharge for 
a full stroke on the other side. In the ordinary compressor of which this is the 
reverse, the valves remain fully open or fully closed, as the case may be, during 



i88 PRODUCTION. 

the entire stroke. With a slide valve just described, the ports area is constantly 
changing from a very small opening through all ranges to the full size of the ports 
and again closing. However, the velocity of the moving piston, which is drawing 
in air on one side and expelling it on the other, is also changing. These two 
changes are, therefore, coincident, and properly related, that is, as the port opening 
of the inlet or outlet side of the cylinder is increasing or decreasing in area, the 
velocity of the inflowing or discharging air is increasing or decreasing as the case 
may be. It is usually true that these complimentary changes are not identical, 
and that the valve may close at a more rapid rate than the piston slows down, 
which causes an increased friction at the port ; this point will be considered later. 

For the present we will take the liberty of assuming the velocity of flow of 
air and the change of valve area as parallel variables. Another point to be 
considered is, that the pressure tending to fill the inlet side of air cylinder is that 
of the atmosphere or 15 pounds. Now it would seem that the limiting speed of 
such an engine would be for any given case that speed which would cause the air 
to flow through the full open port, neglecting now the resistance of pipes, elbows, 
etc., at the same velocity which air would have if allowed to flow through an 
orifice in a receiver, where the pressure is 15 pounds, and the outside pressure 
practically nothing, or from a receiver pressure of 30 pounds to an outside 
pressure of 15 pounds. 

For practical purposes, however, it is better to assume a velocity of flow 
through the port of 100 ft. per second, which is- the figure used for calculating 
port openings for steam engines. 

To make this clearer take the exhauster mentioned by Mr. King. 

The port area is 20 X i^ = 22^/2 sq. ins. or 0.156 sq. ft. 100 X 
60 X 0.156 =: 936 cu. ft. per min. 

The volume of the cylinder, 24 X 18 ins., is 4.75 cu. ft. Dividing 936 by 
4.75, the volume of the cylinder, gives 197 strokes or 98 revolutions per minute. 



COMPRESSED AIR CENTRAL PLANTS. 

The enthusiasm and ingenuity being displayed in the application of com- 
pressed air for power purposes will no doubt bring to light many schemes for 
further advancing its use, now that it is in a fair way to be adopted in so many 
places where a few months ago it would have been rejected — not for the reason 
that it was not competent, but because it seemed new and untried. Many of 
these dormant schemes will be brought out and the fortunate inventor will reap 
a long delayed reward. 

For transmission of power, compressed air perhaps has no equal. It is 
always ready, willing and obedient.There does not seem to exist any of the dan- 
gerous elements that are associated with other forces. Already the central plant 
idea is taking possession of the minds of the mechanical genius of the world, and 
a few of the many devices that may be operated from central plants will be of 
interest to engineers, in general, and will stimulate the adoption of compressed 
air in many places where it is not now applied. We have already told of the 



PRODUCTION. 



1S9 



successful and highly economical operation of various appliances at Jerome Park, 
New York. It is simply a gigantic exhibition of the co-operative system in 
mechanics, where the judicious distribution of power effects good results and 
accelerates the completion of necessary work. 

A proposition has been made wherein one air compressor will supply 
power to run several pumps that are widely separated, for pumping sewage to a 
level of the sewer line in the city of Chicago. 

It seems in this case numerous steam-actuated pumps were to be employed, 
each one of which would require a boiler and an attendant to operate it. A 
progressive firm of pump manufacturers now propose to erect a central air 



COMPRESSOCi. 



o o 

n fi 



3 



I QECtlVER. ( 



OFFICE 

eulLOlNG 

OR 

DWELLING. 



DEEP 
WELL 







AIR 

LIFT 

PUMP. 










r 


1 MAC 


hineI 




111 

a. 


B 


< 


CARPET 

CLEANING 

ESTABLISHMENT. 














loUAPflV. 1 




1 





FIG. 59- 
power plant, lay the pipe line to each pump and operate it by air instead of steam, 
and chances are that they will win the contract. 

These two instances are only given to illustrate the importance to be at- 
tached to this method. 

This little diagram will serve to illustrate the outlines of a central plant 
and its tributaries : 

These and many additional places that may be added could readily be run 
from the one compressor plant, as they may all be within a half mile of each 
other. 

As to the feasibility of this plan, there is no doubt. It has been demon- 
strated, time and again, that by using compressed air for the purposes for which 
it may be employed you will enjoy several advantages over steam and electric 
power. First of all comes safety and cleanliness, then reliability, and the sim- 
plicity with which it may be handled and made to do man's bidding. The cost 
is always dependent upon conditions, but in any case that we can think of it will 
be as cheap as either of the two agents mentioned, and if water power is available 
it will be much cheaper than either of the others. 



190 PRODUCTION. 

COMPRESSED AIR VERSUS TROLLEY. 
To THE Editor — 

In discussing the other day with a New York business man the advantages 
of the Compressed Air Motor over the Trolley, I referred to the safety of the 
former method and its freedom from delays and accidents. He asked me in a 
tone of triumph when I had ever heard of or seen any accident or delay caused 
by the Trolley? 

I was surprised at this question, coming as it did from a man thoroughly 
well informed on current affairs, until I recalled the fact that he lived up-town in 
New York and had rarely "enjoyed" a ride on a trolley car. I am an unfortunate 
resident of trolley-ridden Brooklyn, and the very next day a practical answer 
was afforded me to his inquiry. While riding down Fulton street on a car filled 
with passengers, we were all startled by a sharp explosion directly at the side of 
the car — and a heavy wire blazing and sputtering with blue-fire fell to the ground 
striking the end of the seats, directly in front of me. 

The passengers jumped to the other side amid the screams of women, the 
shouts of men, while every face paled with fright and the stoutest men trembled 
with fear. 

Of course the papers contained nothing of this for it was "only" a daily 
passing occurrence, and my New York friend might say, "but no one was hurt." 
Apparently not, and yet it is now conceded by the doctors, that such frequent 
shocks and frights, leads to prostrations and complications of the nervous system, 
oftentimes most serious. 

Previous to this occurrence I saw a live wire fall upon, and set fire to, the 
roof of the car, and for a hundred feet along the street emitting flames for a min- 
ute or two — a menace to the lives of those crowding the busy thoroughfare. 

The old saying you might as well kill a man outright, as to frighten him to 
death, might with a slight modification be aptly applied to the erratic and terrible 
trolley. 

Yours in the cause of public safety. j. s. tobey. 

BROOKLYN. 



TESTS OF A FOUR-STAGE AIR COMPRESSOR. 

The Engineering News of November 4th contained a clear and valuable 
review of the two tests made on a four stage IngersoU-Sergeant Air Compressor 
by seniors of Cornell University and Stevens Institute, the tests in detail having 
been published in the Engineering Nezvs on October 7th. The method of com- 
puting the efficiency of the Air Compressor defined as "the ratio of the useful 
work done by the air cylinders to the indicated work of steam cylinders," is in- 
teresting and as nearly correct, perhaps, as can be reached under the circum- 
stances. It must be admitted, however, that the work done in the steam cylin- 
ders of this compressor was really more than the figures show, as it is stated in 



PRODUCTION. 191 

the beginning of the Engineering News' article that "the useful work done by 
the air cylinders was the storing in a receiver of 925 cu. ft. of air at a gauge 
pressure of 170 atmospheres." In order to do this, the supply pipe and the high 
pressure air cylinder were also filled with air at the same pressure. The second 
intermediate cylinder was filled with air at 780 lbs. pressure; the first interme- 
diate was filled at 160 lbs., and the low pressure or initial cylinder at 55 lbs. In 
addition to these, the air was forced through the different coolers. It is evident 
that this represents work done, and that it should be taken into account when 
figuring the efficiency of the compressor. Each cubic foot of internal contents 
of conveying pipe required 1,500,000 foot pounds of work at 170 atmospheres. It 
is practically impossible to follow the air through the four stages of compression 
and the intercooling between each stage, comparing and computing the effects of 
each operation successively and obtaining definite results. The efficiency shown 
in the Engineering News' article is certainly as good as could have been ex- 
pected, and it is probably better than has ever been shown before for such high 
pressures. In making theoretical deductions from a test of this kind, the indicated 
horse power of the steam cylinders at the beginning of the series and the volume 
pressure and temperature of the compressed air at the other end are safe lines on 
which to base efficiency. 

It is to be regretted that this test is not conclusive and that the Air Com- 
pressor was not operated under the conditions of actual service. The filling of a 
receiver from atmospheric pressure up to any other pressure, however high, is 
not what a compressor is built for. It has usually to maintain a constant high 
pressure in a receiver while the air is being drawn off and used at that high 
pressure. The first operation is one of compression pure and simple, while the 
second involves not only compression but delivery of the air, which is a very 
different thing. The first operation, which is all that is represented iti these tests 
merely brings the compressor to a point where it is ready to begin its legitimate 
work, and does not show its actual efficiency when at its proper work. It would 
not, therefore, be quite fair or proper to allow the statement of efficiency here 
obtained to go out as showing the actual efficiency of the compressor. 

The results of our computations of the efficiency of the compressor in 
filling the storage receiver only are practically identical with those given in the 
Engineering News. In the first case — the test made by Cornell students — the 
steam cylinders developed 1,556,280,000 foot pounds; and 694 cu. ft. of air, at a 
pressure of 171 atmospheres, was compressed from atmospheric pressure. The 
formula for the mean effective pressure, absolute, in compressing air isothermally 
from any given pressure to any other pressure, we use in this form: 

(Hyp. log R) X P 



R— I 

R being the ratio of the terminal to the initial pressure, and P the absolute 
terminal pressure in pounds per square inch. Substituting the figures we have 

5. 141 663 X 2513.7 

= 76.0268 

170 



192 PRODUCTION. 



« 



The mean gauge pressure then will be 

76.0268 — 14.7 = 61,3268, or say 61.3. 
The power required for the compression will then be 

694 X 144 X 61.3 X 170 =3 1,041,433,056 foot lbs., and 1,041,433,056 ^ 1,556,280,000 
= 66.91 per cent, as the ratio of the work done to the power expended, or the 
actual efficiency. 

In the tests made by the Stevens Institute students, one-third more storage 
capacity was employed, and in the first test the work done was therefore 1,041,- 
433,056 (as above) x i 1-3 = 1,388,577.408 foot lbs. The power developed by the 
steam cylinders being 2,029,500,000, we have 1,388,577,^108 -^ 2,029,500,000 = 6S.40 
per cent. 

In the second test by the Stevens Institute students, the final volume and 
the total work done was the same as in their fi.rst test, with the exception that 
at the beginning of the second test the receiver was already filled with air com- 
pressed to 136 atmospheres, and the work of this preliminary compression is to be 
computed and deducted. The hyp. log. for 13.6 being 4.912655, and 136 x 14.7 = 
1999.2 pounds, the absolute pressure, "we use these in the formula ahove and we 
have 

4.912655x1999.2 

= 72.75. Then 

135 

72 75 — 14.7 == 5805 the m. e. p. Then 925 x 144 x 58.05 x 135 == 1,043.855,100 
foot pounds, and 1,388,577,408 — 1,043,855,100 = 344,722,308 foot pounds, the worU 
actually done. As the power developed by the steam cylinders was 527.710,000, 
that is to be used as a divisor, as in the preceding cases, so 344,722,308 -^ 527,710,- 
oco = 65.3 , jcr cent. ^^^ 

This is practically a recapitulation of the Engineering News' figuring, but 
it represents independent computation all through. The results differ only as the 
work of any one computor may differ from that of another on account of dif- 
ference of practice in the retention of the decimals. It confirms in every par- 
ticular the results arrived at. 

A quite simple means of ascertaining the ultimate efficiency of the com- 
pressor, at any particular moment of its operation, would have been to take a 
simultaneous set of indicator diagrams, as was done repeatedly by the students, 
and note at the same time the temperature and pressure of the air delivered. The 
steam cylinder cards would, of course, show the power developed, and from the 
card of the first or low pressure air cylinder the volume of free air taken in 
could be ascertained. It would not be necessary to pay any attention to the work 
of the other air cylinders. The temperature and pressure at delivery would sup- 
ply all additional data required, so far as the mere computation of the efficiency 
was concerned. The card from the high pressure cylinder could not be expected 
to be minutely accurate, on account of the small area of the piston and the friction 
and other interfering conditions. The entire set of cards is, of course, valuable, 
and especially suggestive and instructive to the compressor designer as showing 
the relative economy of each stage of the operation and the inter-dependency of 
the different parts of the apparatus. 



PRODUCTION. 193 

ABSTRACT OF THESIS TEST OF COMPRESSED AIR POWER PLANT 
AT JEROME PARK, N. Y. 



By George W. Vreeland and Charles M. Younglove. 



To receive the degree of Mechanical Engineer at Cornell University, the 
above named gentlemen sought to satisfy the requirement for a graduation 
thesis by making an exhaustive test on the Compressed Air Power Plant at 
Jerome Park, N. Y. 

The purpose of the test was to determine the various efficiencies of a central 
power plant of this kind and point out any line of improvement that may be 
necessary. 

A complete description of the plant was given in Compressed Air, No. 7, 
Vol. I., and it will not be necessary here to go into details further than say that 
the plant consists of 2 Hogan boilers with an aggregate of 540 h. p., and one 
Ingersoll-Sergeant Corliss Cross-Compound Condensing Air Compressor, the 
equivalent of 3,400 cubic feet free air per minute at a pressure of 80 lbs. 

The use to which compressed air is put to at Jerome Park represents a 
d^'paimre i^'-om old methods. Although the relative advantages are pretty well 
\ii !'. - . d by those interested, any reliable information on any part of the plant 
is ot 1 'I "''••"'•" ind great care was |]j|erefore taken in this test to give exact 

«-i' :>iir 

' ^'" .~,ariiDles of indicator cards taken trom all cylinders of the com- 
:d give the following abstracts, which no dctrh* will interest our renders. 
A — Report of boiler test. 
B — Engine data and results. 
C — Compressor data and result*. 1^ r 

REPORT OF boiler TEST. 

Duration of trial, hours, 10. 

Dimensions. 

Grate surface Sq. ft., 121 

Water heating surface " 5548 

Superheating surface " None 

Area for draft (Calorimeter) " 

Area, chimney " I973 

Height, chimney Ft. 93 

Ratio heating surface to grate surface 45-8 :i 

Ratio air space to grate surface 

Pressure. 

Barometer Inches, Mercury, 29.7O 

Steam gauge Pounds, 1 16.5 

Absolute steam pressure Pounds, 131. 14 

Temperature. 

External air Dog.. Fah.. 65 

Boiler room " 79 

Flue '• 483.5 



194 



PRODUCTION. 



Temperature — Continued. 

Furnace Deg., Fah.» 1918. 

Feed water " 105.8 

Steam " 259.05 

Fuel. 

Total coal consumed Lbs., 9284 

Moisture in coal Per cent., 2.22 

Dry coal consumed Lbs., 9078 

Total refuse, dry " 1102 

Total refuse, dry Per cent., 12.1 

Total combustible Lbs., 7976 




FIG. 60. — INDICATOR CARDS FROM CORLISS COMPOUND AIR COMPRESSOR AT JEROME 
PARK, N. Y., TAKEN APRIL 6tH, 1897. 

Fuel per Hour. 

Dry coal, per hour Lbs., 928.4 

Combustible, per hour " 797-6 

Dry coal per sq. ft. of grate " 7.67 

Combustible, per sq. ft. of grate " 6.59 

Quality of steam Per cent., 97.9 



PRODUCTION. 

Total Water. 

Total weight water used Lbs., 

Total evaporated, dry steam Lbs., 

Factor of evaporation 

Total from and at 212° Lbs., 



t95 



84,510 
82,735 

1.154 
95476 




FIG. 61. — INDICATOR CARDS FROM CORLISS COMPOUND AIR COMPRESSOR AT JEROME 
PARK, N. Y., TAKEN APRIL 6tH, 1897. 



Water per Hour. 

Amount used Lbs., 845 1 

Evaporated dry steam Lbs., 8273 

Evaporated fi-om and at 212° Lbs., 9547 



196 PRODUCTION. 

Economic Evaporation. 
Per pound of fuel. 

Actual per pound, dry coal , Lbs., 9.1 1 

Equivalent from and at 212° (dry coal) Lbs., 10.51 

Per pound of Combustible. 

Actual Lbs., 10.37 

Equivalent from and at 212° " 1 1-95 

Per sq. ft. Heating Surface per hour. 

Actual Lbs., 14.9 

Equivalent from and at 212° " 17.19 

From 100° Fah. to 70 lbs. by Gauge. 

Per pound of fuel Lbs., 8.57 

Per pound of combustible " 9.5 

Evaporation per Hour. 
Per sq. ft. of Grate. 

Actual from feed water temperature Lbs., 68.37 

Equivalent from and at 212° " 78.89 

Per sq. ft. of Water-Heating Surface. 

Actual Lbs., 1.49 

Equivalent from and at 212° " 1.71 

Horse Power. 

On basis 347/2 lbs. equiv. evap. per hour (i) H. P., 277 

Builder's rating H. P., 510 

Ratio of commercial to builder's rating 50.5 % 

Heat generated per hour B. T. U., 1 1465740 

Heat absorbed per hour " 8960200 

Heat lost per hour " 2505540 

Efficiency of boiler Per cent., 78.I 

Efficiency of furnace " 78 

ENGINE DATA AND RESULTS. 

Kind of engine, Cross Compound. 

Duration of run 10 hours. 

Revolutions per minute 57.o6 

Diameter of fly-wheel 22' 

Weight of fij'-wheel 50,201 lbs. 

Temperature engine room 78 

Temperature external air 65 

Temperature condensing water, cold 74.3 . 

Temperature condensing water, hot 113.8 

Temperature boiling point (atmospheric pressure) 21 1.7 

Boiler pressure, gauge 1 16.5 

Boiler pressure, absolute 131.03 

]^)arometer in mercury 29.73 

Barometer pressure in lbs 1458 

(1) standard Commercial II. P. 



PRODUCTION. 197 

Condenser in mercury 23.3 

Condenser pressure in lbs 11.04 

Total condensing water per hour, lbs 160360. 

Weight condensing water per pound steam 19.7 

Total I. H. P 467.7 

Total D. H. P. .• 402.4 

Mechanical efficiency 86.03 % 

Moisture in steam 2.1 % 

Steam per I. H. P. per hour, actual 17.36 

Steam per I. H. P., corrected for Cal 17.01 

Water rate of perfect engine 12.4 

Thermodynamic efficiency 23.4 

Ratio actual to theoretical water consumption 1.37 

Heat supplied per hour, B. T. U 9634245.8 

Heat discharged and radiation, B. T. U 8456808.8 

Heat utilized, B. T. U 1 177437.0 

High. Low, 

Diameter of cylinder in inches 24 44 

Length of stroke 48 48 

Diameter of piston rod, front 4 5 

Diameter of piston rod, back s^ 3^ 

Piston displacement, crank end, cu. ft 12.21 1 41.64 

Piston displacement, head end, cu. ft 12.221 41.92 

Volume of clearance, head end, per cent 3^ 4 

Volume of clearance, crank end, per cent 314 4 

Make of Indicator Thompeon. Tabor 

Scale of spring 60 10 

Cut-off, crank end, % stroke 24.82 16.83 

Cut-off, head end, % stroke 22.14 16.32 

Release, crank end, % stroke 100 100 

Release, head end, % stroke 100 100 

Compression, crank end, % stroke 100 100 

Compression, head end, % stroke 100 100 

Ab.solute pressure at point cut-off, crank 120.58 26.23 

Absolute pressure at point cut-off, head 119.98 25.53 

Absolute pressure at release crank 27.63 4.16 

Absolute pressure at release cut-off, head 26.58 3.99 

I H. P., head 123.3 I0474 

I. H. P., crank 127.44 1 12.24 

Total I. H. P 250.74 216.98 

Steam per I. H. P. at point of cut-off, per diagram, high pressure cylinder. . . 11.3 
Steam per I. H. P. at point of cut-off, per diagram, low pressure cylinder. . 7.25 

COMPRESSOR DATA AND RESULTS. 

No. L No -3. 

No. of cylinders, double-acting i ' 

Length of stroke, in inches 48 4^ 



PRODUCTION. 



Diameter of piston 24% 

Piston area, head, sq. inches 429.28 

Piston area, crank, sq. inches 451-49 

Diameter piston rod, in inches 3% 

Diameter piston in inlet, inchfes 6 7-16 

Piston displacement, per stroke, in cu. ft., head 11.924 

Piston displacement, per stroke, in cu. ft., crank 12.54 

Clearance, head, % volume 289 

Clearance, crank, % volume 287 

Displacement of piston, cu. ft., per minute 1395.68 

Developed H. P. mean 198.9 

Absolute pressure at end of compression 80.76 

Heat equivalent of work, steam end, per hour 

Heat equivalent of work, compressor, per hour 

Efficiency of mechanism, % 

Work of compression per lb. air, in ft. lbs., Adia 

Work of compression per lb. air, in ft. lbs., Isoth 

Efficiency of compression 

Combined efficiency, 86.03 X 82.05 

HEAT ACCOUNTS. 

No. 1. 
Temperature of air at inlet 78 

Temperature of air at exhaust 354-7 

Rise of temperature of air 276.7 

Temperature of entering jacket water 46.05 

Temperature of exit jacket water 95.7 

Rise of temperature of jacket water 49.65 

Weight of jacket water per hour 2934.6 

Heat rejected in jacket water (B. T. U., per hour) 145705. 

Heat rejected air leaving cylinder (B. T. U., per hour) 308063 

Radiation and unaccounted for 13701 

Total heat loss 467469 

Heat produced in compression 467469 

Calculated volume of air delivered in cu. ft. per stroke at 

atmos. pressure, allowing for clearance and by pass. . 12. 11 

Per minute, cu. ft 1395-68 

Per hour, cu. f t 83740 

Rated capacity of compressor at 60 revolutions per minute, 

in cu. ft. of free air 1467 

Per cent, of rated capacity delivered 95 % 

Weight of comp. air per hour 12393.6 

Weight of comp. air per D. H. P 

Volume of air delivered per I. H. P. per hour at atmospheric 

pressure, in cu. ft 

Volume of air delivered per D. H. P. per hour at atmospheric 

pressure, in cu. ft 

Weight of water in cooling i lb. of air, in lbs 



24 j4 
429.28 

451.49 

3H 

6 7-16 

11.924 

12.54 

.289 

.287 

1395.68 

204.5 

82.20 

1177437 

I 0239 10 

86.03 

7658.53 

6286.44 

82.05 

70.58% 

No. 2. 
78 
360.03 
282.03 

4605 
92.03 
4598 
2934.6 
134935. 
313865 
18669 
467469 
467469 

I2.II, 

1395-68 
83740 

1467 
95% 

.517 

358.09 



416.2 



.31 



PRODUCTION. 199 

In accounting for mechanical efficiency of 86.03%, allowance must be made 
for the work of the jet condenser, which is attached by means of bell crank and 
connecting rod to crank pin of low pressure engine — pumping about 200,000 
pounds of water per hour with a suction of 5 feet, and also from a varying load 
as well as the condition of condensing water which enters condenser at a high 
temperature. This is occasional by a limited supply. The water being used 
over and over again, does not have time to cool, thus reducing the vacuum and 
decreasing the mechanical efficiency and increasing the steam consumption per 
H. P. per hour. 



TESTS OF A KING-RIEDLER AIR COMPRESSOR, AT THE ROSE 
DEEP MINE, SOUTH AFRICA. 



PAPER READ BY MR. L. I. SEYMOUR^ BEFORE THE SOUTH AFRICAN ASSOCIATION OF 
ENGINEERS AND ARCHITECTS. 



ENGINE. 

A Vertical King-Riedler Compound Steam and Double Stage Air Com- 
pressor at the Rose Deep, Ltd., No. i Shaft. 

Diameter of high pressure eteam cylinder 19 inches stroke 4r6875 inches 

" low " " " 30 '"■ " 41-9375 " 

" " Ist stage air cylinder 30 " " 41-9375 " 

" 2d " " " 17-5 " " 41-e875 " 

" piston rods ... . 3-46875 feet 

The two steam piston rods are connected by a short link to a triangular 
connecting rod, and the power from them transmitted through a crankshaft, fly- 
wheel and another triangular connecting rod and links to the two air cylinders. 

The inter-cooler for the air is placed on the platform by the side of the air 
cylinders. (N. B. — This inter-cooler was not very effective and is now being 
fitted with baffle plates, which will reduce the temperature of the air in the inter- 
cooler to less than that drawn into the ist stage cylinder.) 

The circulating pump for inter-cooler and water jackets was driven directly 
by the engine. 

The air pump and jet condenser was disconnected. 

JACKETS. 

The high pressure steam cylinder jacket was under boiler pressure, while 
the low pressure steam cylinder jacket was reduced to a pressure from 30 to 40 lbs. 
per square inch by a "Royle" reducing valve. The jackets were drained by a 
"Kieley" trap, and the discharge weighed. 

CONDENSER. 

A "Wheeler" independent condenser (capacity, 30,000 lbs. of steam per 
hour) with Admiralty tubes and attached horizontal air and circulating pumps, 
steam cylinder 16", air pump 16", circulating pump 18" x 24" stroke, was used 
during this trial entirely for the compressor; although ordinarily it condenses 
for the compressor, a 12^'' and 19" x 42" Cornish pumping plant, a small tem- 
porary lighting plant and a pair of 10-^2" and 17" x 28" horizontal tandem com- 



200 PRODUCTION. 

pound "Tangye" winding engine. The steam actuating the motive cylinder ex- 
hausted directly into the condenser, and all the steam used was charged against 
the compressor. The discharge from the condenser air pump was not measured 
the water pumped into boilers being weighed. 

BOILERS. 

The two boilers in use were of the horizontal return tubular type, (see 

annexed sketch). 

Diameter of shell in inciies 66 

Length between tube plate in feet 16 

Nnmber of tubes in each boiler 104 

Outside diameter of tubes in in ches 3 

Number of square feet of grate surface 35 

" '• " '-heating " 1500 

Ratio of grate to heating surface 1*428 

No economizers were used with these boilers. A separator was fitted on 

the steam main to compressor and drained by a "Kieley" trap. 

The water discharged from this tray was weighed, 

COAL. 

The coal used was "Clydesdale," having an evaporative value under the 
conditions of the trial of 5.815 lbs. of water per lb. of coal, (3 of rounds to i of 
nuts). 

DRILLS. 

One 2-1/2 inches value compared to 334 inches Tngersoll-Sergeant drill 445 

Eleven 3-1/4 " " " '• " " " " " 1-000 

Seven 3-5/16 " " " " " " " ». " 1 069 

Twelve 3 3/8 " " " '' " " " " " 1'123 
Total 31 drills, equal in value to 32'4 334 incli drills', 

TABLE 16. 



Name of Drillman. no\eI 


MfchlSL. !"">•»-- 


Remarks. 


J. Stephens 

D. McAvoy 


7 
2 
8 
6 
9 
2 
1 
8 
4 
8 
9 
8 
15 
8 
9 

10 

i 

8 

7 


2 
2 
2 
2 
2 
1 
2 
2 
2 
2 


1 
19 feet 7 inches 
8 " 2 •' j stopped after about 2 hours 

36 " 5 •' ! 
29 " 5 " i 


D. McAvoy 

K. Wilson 


G. Tonkin 


51 " 9 " 
11 " 5 " 
3 " " 
40 " 6 " 
19 " 5 " 
48 " 9 " 
46 " 2 " 

44 " 8 •' 
85 '• 11 " 
42 " 4 » 
42 " 1 " 

45 " 8 " 
50 " 8 " 
32 " 9 " 
58 " 5 " 
44 ■' 7 " 
42 " 3 " 
35 " 3 " 


4 dry holes 


Walters 


Wallers 


stopped after about 1 hour 


T. Mylroie 


J. C. Mylroie 

H. Tembv 




R. Dellbridge 


3 '• 


S. Uren 

T. H. Trevillion 

J. H. Harris 




J. Cock 


4 di-y holes 


H. Carnow 


Blain 


4 dry holes 




J. A. Harris 

Cock 

J. Harrison 




J. Handley 








Totals 


159 


31 


2:30 feet 2 inches 


18 dry holes 





Thirty-one Ingersoll-Sergeant drills were started at 9:45 a. m, (Mine time), 
all being set up and ready to start simultaneously. The air pressure at the start 
was 46 lbs, per square inch, and as this could not be raised with the compressor 



PRODUCTION. 2ot 

running at about 90 revolutions per minute, two drills were stopped after drilling 
8 ft. 2 ins. and 3 ft. respectively. The pressure then gradually rose 70 lbs. per 
square inch. Twice afterwards it fell to 48 lbs. and three times rose to 95 lbs. 
finishing at 80 lbs. (per square inch at 3 145 p. m. the average pressure was 69,83 
lbs.) 

The size of drills (all Ingersoll-Sergeant). 

Two of the 3J4 in. drills ran 2 hours and i hour respectively. 

This reduces the average time of running of the 32-4 314 in. drills from 6 
hours (duration on trial) to 578 hours, which is equivalent to 30*9 3^ in. drills 
running for an average time of 6 hours. 

N. B. — The comparative values of the drills was measured by filling the 
cylinders, ports, etc., with water. 

All holes not indicated were wet holes. 

A bonus of £$ was given to C. Tonkin for drilling the most footage with 
his machine. The footage of 30.0 drills averages 26 ft. 10 2-5 in. per drill in 6 
hours which is equal to 4 ft. 5 11-15 per drill per hour. 



DATA. 

Duration of trial in hours 

Average height of mercurial barometer in inches (corrected) 

" pressure in lbs. per square inch 

" UK steam by gauge 

" " " '• (absolute) 

"■ vacuum in inches of mercury 

" pressure of air in intercooler 

" " " "receiver 

" temperature of air entering 1st stage air cylinder in degrees Fah. 

" " •♦ leaving " "• '• ** 

" " " entering 2d stage " " " 

i. 4< K leavins: " " " " 

'• " " at drills iu mines in degrees Fah 

Percentage of volume taken Dy 2d stage air cylinder to that discharged 

by let stage air cylinder 

Percentage of volume taken by 2d stage air cylinder to that discharged 

by l6t stage air cylinder, if air had been reduced by proper inter- 
cooling to temperature used at drills 

Number of revolutions of engine during trial 

Average number of revolutions per minute 

" temperature corresponding to absolute steam pressure in 

degrees Fah 

Average temperature of feed water 

B. T. U. in each lb. of the dry steam 

" " " feed water 

•' absorbed by each lb. of the feed water 

Factor of evaporation 

Lbs. of water pumped into boiler 

" moisture in the steam 

Factor of dryness of the steam 

Lbs. of dry steam used by steam jacket 

" " " engine (including indep. condenser) 

Total lbs. of dry steam used by engine (including steam for jacket and 

independent condenser) 

Total lbs. of dry steam used by engine (including steam for jacket and 

independent condenser) per hour 

Lbs. of water used by condenser ( by meter) 

" " " per lb. of steam condensed 

Temperature of water entering condenser in degrees Fah 

" " leaving " " " 

B. T. TJ. in each lb. of water entering condenser 

" absorbed by each lb. of the circulating water 



52-0 
292-8 
131- « 
243 5 

650 



24 5 

12 04 

105-39 

117-43 

21-24 

27-0 

69-83 

5430 

753-8 

592-9 

704-5 

526-0 

78-65 



69 78 
29916-0 
831 

339-37 
98-0 
1317-45 
98-97 
1119-38 
1-139 
46878-8 
422-85 
99- 16 
.3071-0 
43380 25 

46451-25 

7741-87 
1434500-0 
83 07 
79-79 
106-45 
79 85 
26-71 



abs 



RESULTS. 



I. H. P. of steam cylinders 

" " air and circulating pump. 

TotalLH.P. of engine 

L H. P. of air cylinders 



873-65 

19 51 

893- 16 

338 77 



202 PRODUCTION. 

Mechanical efficiency of engine per cent 86-17 

" " " ^without including air and circulating 

pumps) per cent 90'66 

Lbs. of dry steam used by engine and independent condenser per 

I. H. P. per hour 8-39 

Lbs. of dry steam used by jacket per L H. P. per bour 1-30 

Total lbs. dry steam used per 1. H. P. per hour 19.69 

Lbs. of coal used per I. H. P. per hour (assuming 1 lb. of coal will 

evaporate 674 lbs. of water from and at 212" Fah. cost of coal 13/9 

per20001bs.) 3-38 

Cost of coal per I. H. P. per hour in pence 0*28 

Heat efficiency of engine per cent 10*7 

Average volume of free air entering 1st stage cylinder in cubic feet per 

minute 2505" 5 

Average volume of air leaving 2d stage cylinder at 69*83 lbs. gauge 

pressure and at the temperature used at drills (65** Fah.) in cubic 

feet per minute 388-46 

1. H. P. at compressor steam cylinder per 3>4 in. drill 12-72 

Cubic feet of free air required per 3^4 ™' drill per minute including 

all leakages 81-08 

Lbs. of coal required per drill per hour 4'^^99 

Cost of coal per drill per hour in pence 3-55 

SUMMARY OF MAIN DETAILS. 

Diameter of high pressure steam cylinder 19 inch stroke 41 '6875 

low " " 30 " 41-9375 

" 1st stage air cylinder 30 " 41-9375 

2d '' " 17-5 " 41-6875 

Average revolutions per minute 83' 1 

" steam pressure (by gauge) 105"39 

" vacuum (by gauge) 21 • 24 ins. 

•' intercooler air pressure (by gauge) 27-0 

receiver " " 69 83 

" temperature of air entering 1st stage cylinder in degrees Fah. 82-0 (.543 abs) 

" " " at drills in degrees Fah 65-0 (526 ") 

Actual number of 8J4 inch drills working 30-9 

Duration of trial in hours 6-0 

Total footage of holes drilled 830 ft. 3 inches 

Average " " per machine 26 " 10 2-5 inches 

Cubic feet of free air compressed per minute 2505-5 

" " air at drills per minute at 6983 lbs. pressure and 65*^ Fah. 36846 

" " free air used per 3J4 inch drill per minute 81 "08 

'■'■ " air used per drill per minute at 69-83 lbs. pressure and 

65° Fah 11-92 

Average I. H. P. of steam cylinders (including air and circulating 

pump) 39316 

Average L H. P. of air cylinders 338-77 

Mechanical efficiency percent 86-17 

Average steam I. H. P. per drill 12-72 

" feed water to boilers per I. H. P. per hour 19-69 

" cost of coal per drill per hour in pence 3-56 

Tested February i6th, i8g8. 

I believe the footage drilled during these six hours actual work is equal 
to the average work done per shift of drilling, which is usually of eight hours 
duration; on account of the drills being all set up ready to work and also the 
incentive, etc. 

In other words I do not think the compressor would have made many more 
revolutions during eight hours ordinary working, than it did during the six hours 
trial. If this be true then the average steam horse power per drill would be 
reduced by 12-72 X 6 -^ 8 = 9-54 or the probable steam horse power actually 
required per drill. 

It must be borne in mind that this machine was specially designed for a 
high speed, with large valves having a high lift. 

In addition to this, the air pipes at the Rose Deep, are remarkably free from 
leaks. Against this, the drill pistons are made a good fit in their cylinders and no 
packing rings are used. 



PRODUCTION. 203 

Were the compressor only charged with its pro rata of the power required 
by the air and circulating pumps, as ordinarily used, the result would have been 
better. 

Three other trials have been made since, which demonstrate that the total 
steam used per indicated horse power is i -2 lbs. less, where the jackets are not 
used, than has been obtained on this trial. 

I should not like to state this as being true under all conditions, inasmuch 
as the steam at the compressor is very dry, and were it moderately wet, no doubt 
the performance with jackets would be better than without. 

Two boilers easily ran the compressor, and during a later trial which was 
non-condensing, the same two boilers ran the compressor but with hard firing. 

The steam used in this latter trial was 25 75 lbs. per indicated horse power, 
over 31 per cent, more than when condensing. 

The lbs. water evaporated into steam per boiler per hour was 3871 equal to 
2 -58 lbs. per square foot, heating surface, while on the non-condensing trial this 
was nearly 3 -35 lbs. water evaporated per square foot per hour. 

The cubic feet of free air compressed per minute was calculated from the 
first stage air cylinder card, the points at which the compression and re-expansion 
Imes across the atmosphere, being taken as the volume of air actually delivered, 
which was 88 -4 per cent, of the theoretical cylinder volume. 

The compressor had been in constant use for three years, with few repairs, 
the only alterations being to substitute forged steel connecting rods in place of the 
original cast steel ones, which had proved defective. 

The fluctuations in the air pressure were on account of the governor being 
disconnected and the speed regulated by hand. 

The latter type of intercoolers supplied with these machines, in which the 
air is made to cross the cooling tubes three times instead of moving lengthwise, 
is a decided improvement and adds materially to the economy by reducing the vol- 
ume of air discharged by the first stage cylinder and compressed by the second 
stage from 78.65 to 69.78 per cent. 

Having proved that with this compressor running at a high rate of speed 
we compress 382 *3 cubic feet of free air at 12 lbs. atm. pressure to a pressure of 
69.83 lbs. per square inch, per steam indicated horse power per hour. I reserve 
for a future discussion and paper, the amount of air necessary under conditions 
existing on these fields, to again generate one brake horse power and I trust by 
this means we may obtain some reliable data of the efficiency of transmission of 
power by compressed air, for comparison with other methods more in use. 



CENTRAL POWER PLANTS. 



Central Power Plants for distributing any kind of power, either Com- 
pressed Air, Electric or belt power, are gaining daily in popularity, and it is only 
a question of time until small power consumers will derive their power from 
Central Power Plants instead of generating the power themselves. By doing so 
Ihey will dispense with the following items : Expenses of installing boilers with 



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PRODUCTION. 205 



their expensive settings and piping, economy in space, dispensing with the services 
of expensive and many times unreliable engineers; and they will obtain their 
power at reduced prices from Central Power Stations operated in an economical 
manner. 

The block system of distributing power has been tried in this city for the 
last few years, and while working under most unfavorable conditions it has 
proved to be a financial success to both owners and consumers. 

The table which the writer publishes in connection with this article, and 
which is compiled not only from theory but from actual practical results, will 
demonstrate the adaptability and necessity of Central Power Plants. The larger 
the Central Plant is the greater will be the economy. 

When a Company has decided to install a Power Plant the first problem 
which presents itself for solution is the selection of engines and boilers and other 
machinery to economically develop this power. Assuming that there is sufficient 
f^Ioor space to install the Plant to suit the best obtainable conditions and that the 
purchasers have enough business sagacity to make the first cost secondary to ulti- 
mate economy, then in order to make a proper selection the following points only 
should be considered : Whether to install single cylinder, compound or triple ex- 
pansion engines, either condensing or non-condensing; whether, according to 
price of fuel, ordinary return tubular or high pressure water tube boilers would be 
most advisable; whether for condensing purposes, jet or surface condensers are 
preferable. For small plants up to 50 H. P. where the cost of fuel does not 
exceed $4.00 per ton, plain slide valve engines will generally do, as they hardly 
require any attention, but the fuel consumption per H. P. per hour for this class 
of engine is exceedingly high. For plants varying from 50 to 100 H. P. per unit 
Meyer's cut-off engines will fill the bill. For powers varying from 100 to 500 H. 
P. either single or compound Corliss engines, either non-condensing or condens- 
ing, are advisable, according to conditions, it being natural that the compound 
condensing Corliss engines will be most economical. A reference to the table of 
cost of plant will show conclusively that the first cost of a plant cuts a very small 
figure in comparison to the cost of its operation or economy, and that the extreme 
difference in price between the cheapest plant for 1,000 H. P. in engines of ade- 
quate sizes shown in column No. 2 to the expensive but economical plant shown in 
column No. 8 and amounting to $50,000, is more than recovered the first year in 
the consumption of fuel. As shown by the above table it is understood that the 
plant is in operation for 24 hours per day with cost of combustible at $4.00 per ton. 
the figures being based on regular mining or railroad work. The cost of operating 
such a plant in the Western States generally exceeds the above figures, as the 
price of fuel, labor and incidentals is higher than that named above, and thus a 
higher percentage of saving will be prevalent. Economical advantages of com- 
pounding and condensing contrasted with the old style of single cylinder non- 
condensing engines are so patent that no company could be oblivious to them and 
be prejudiced in favor of buying fuel-eating plants as a slightly smaller initial 
expenditure. 

No reference is made in the above table regarding the cost of labor to 
operate plants, the cost of labor depending entirely upon the region where plant 
is installed; however, it should be understood that niriniial labor required to opcr- 



2o6 PRODUCTION. 

ate a i,ooo H. P. Central Power Plant will not exceed twice the labor required 
for a single 200 H. P. plant. 

The table published in connection with this article ought to be of interest to 
any party contemplating the installation of a Compressed Air Central Power 
Plant for the distribution of power to small consumers. 

Much has been said recently on the subject of distributing compressed air 
power for automobile vehicles and manufacturing purposes, but in all that has 
been published nothing has been said showing the cost or giving any data to guide 
the investing public in this matter. F. schmerber. 



A CENTRAL POWER SCHEME. 

A company is at present in course of formation to be called "The Kal- 
goorlie Goldfields Electromotive Power Compressed Air and Electric Light Com- 
pany, Limited." The object of the company is to establish a central power sta- 
tion on a site conveniently situated for the supply of electromotive power, com- 
pressed air, and electric light to the group of the larger gold mines on the Kal- 
goorlie goldfields. The Kalgoorlie miner speaks of the project in this manner. 

There is probably no better field in the world for the successful carrying 
out of such a scheme than the Kalgoorlie goldfields, as the best mines are sit- 
uated in a compact group, so that the distance of the mine most remote from the 
central station as suggested in this scheme will not exceed a mile, while the 
majority of them will be less than half that distance. Within a radius of two 
miles there are about fifty leases that are on payable gold, which in the near 
future will require power, at as cheap a rate as possible. 

Mr. Sam Wilson, mechanical and mining engineer, Coolgardie and Kal- 
goorlie, is the chief promoter of the Kalgoorlie central power scheme. During 
the last twelve months he has been acquiring information and data respecting the 
same, not only here, but from all parts of the world, wherever accumulative 
power is being used. As the founder, managing director and largest shareholder 
of the Pioneer Foundry and Engineering Works in this place, Mr. Wilson has 
had special opportunities of becoming acquainted with nearly all the mine man- 
agers and electrical and mechanical engineers on the field, all of whom, without 
exception, recognize the fact that a large central power company will do more 
to develop and encourage the mining industry than anything else. Mr. D. C. 
Smith, electrical engineer of the Kalgoorlie Council, has given valuable assist- 
ance to the promoters of the Kalgoorlie central power scheme by his practical 
and technical knowledge. 

It has been ascertained that, with one or two exceptions, there is no mine 
in the Kalgoorlie district able to produce power for less than from 6s. 6d. to 7s. 
per i. h. p., per 24 hours, and the average cost is usually higher than this. The 
proposed company does not intend to charge more than 4s. per i h. p., thus 
effecting a saving of at least 25 per cent. Fourteen mines are at present using 
about 3,600 i. h. p., so that the profit these mines would make by taking their 
power from the Central Power Company's works would be over iioo.ooo 
per 365 days working, still leaving a very handsome profit for the company. 



PRODUCTION. 207 

The company proposes to at once erect a plant that will generate 3,000 i. 
h. p. for compressed air, to work 300 rock drills, and for underground hauling 
and pumping, 2,000 i. h. p. electromotor power, for winding, crushing, pumping 
and every other purpose; and 300 h. p. for electric lighting. It is thought that 
double this power will be required before the plant is completed. The capital 
of the company is £500,000, and it is proposed to call up £300,000 at once. Some 
months ago the promoters put this scheme, with all the required data and par- 
ticulars, into the hands of Mr. William Griffith, the representative of Messrs. 
Bainbridge, Seymour & Company, the large mining engineers, St. Helen's place, 
London, who perceived its importance, and he at once forwarded all particulars 
to London. Through the able assistance given by Mr, Griffith and his firm, the 
scheme has been taken over and registered by a wealthy, influential syndicate 
in London, the chairman of which is also chairman of one of the largest electric 
lighting companies in London. 

The syndicate has received very great encouragement from the largest 
mining boards in London, and it is thought that they will subscribe half the 
required capital, as they will be the most benefited by the company, and thus 
share half its profits, and secure equal representation on the London and local 
boards which will control the company. As the power will be registered by 
meter at the different mines, only what is used will be paid for. Each mine 
will provide its own receivers for compressed air; the electromotors will be the 
property of the power company, and a rent will be charged for their use and for 
keeping them in order. 

In order to guarantee continuous power a reserve plant will be kept ready 
for use in case of a breakdown ; accumulators will also be used for storing both 
compressed air and electricity for several hours, which can be drawn upon when 
required. 

To the non-producing mines, to those which are being developed, and 
especially to those with small capital, the advantages are incalculable, as such 
mines will be saved the expense of putting down power and compressor plants, 
and will only be called upon to pay for the power and compressed air used. This 
should prove a great inducement to many developing mines that are at present 
closed. There is very little doubt that before the year is out all the power used 
about Kalgoorlie for lighting and other purposes will be drawn from the central 
power. 

The scheme and plans are at present before a board of mechanical and 
mining experts in London, and it is expected that one or two of them will be 
here in a week or two to consult with the local promoters, and in a few weeks 
at most the company will be placed on the London market. 

It has been ascertained from the local representatives of several of the 
principal mines that they would be willing to give their support to such a scheme, 
and it is proposed in the first instance to put down plant sufficient to supply 
their requirements, with a fair margin to meet any further demand. The fol- 
lowing table gives a list of some of the principal mines, with the approximate 
power, number of lamps required for lighting, a probable number of compressed 
air drills either in use now or required in the near future: 

It has therefore seemed reasonable to base the accompanying estimates on 
the following figures: 



2o8 



PRODUCTION. 



2,000 actual h. p. delivered on the mines for crushing, pumping, hauling, winding, 

etc., by means of electromotors. 
300 actual h. p. in the form of electric light. 

2,000 actual h. p. delivered on the mines in the form of compressed air. 
4,300 total actual h. p. delivered. 

But as the losses of transformation and transmission in the electric power 
and light circuits will amount to about 30 per cent., and the losses in air trans- 
mission to 50 per cent., the total h. p. generated in the central station will amount 
to 5,443 h. p., and this figure has been adopted in calculating capital and working 
expenses. 

From these estimates it will be seen that the capital actually required is 
^235,500, but as it is anticipated that an early extension of plant will be necessary, 
it is proposed to have an authorized capital of £500,000 and to call up £300,000 at 
once, which will leave a sufficient margin for running expenses, while the plant 
is being filled up, the balance to be held in reserve toward duplicating the power, 
which more than probable will be necessary at an early date. 

The annual running expenses will amount to £117,093, and the gross 
revenue, by charging 4s. gd. per actual h. p. delivered, or 3s. I7d. per electric unit, 
will be £214,747 los., leaving a profit of £97,654, equal to a profit of 32 per cent, 
on £300,000. 

To give mine-owners a direct inducement to become consumers, it is pro-, 
posed to give them the opportunity of subscribing conjointly one-half of the re- 
quired capital, the other half being offered to the public, and it is further pro- 
posed to make the shares held by the mine-owners preferential to the extent of 
paying 6 per cent, on the capital held by them as a first charge on the profits. 

TABLE 18. 



No. of 

Drills 



No. of 
16 C. P. 
Lamps 



H. for 

other 

purposes 



T^otal 
H. P. 



For 274 days 



Present 
Cost at 6/6 



Cost at 
4/9 



Saving 



Australia 

Lake View 

Great Boulder 

Ivanhoe 

Go] den H ors eshoe . . 

Kalgurli 

Kalgurli North 

Kalgurli South 

South Boulder 

Hainault 

Brookmau's Boulder 

Boulder No. 1 

Perseverance 

Oroya 

Totals 



211 



200 
200 
150 
200 

im 

100 
100 
100 
50 
50 
.50 
50 
50 
50 



1,500 



700 


870 


240 


385 


240 


345 


150 


245 


1.50 


240 


100 


170 


ICO 


170 


100 


170 


100 


165 


100 


165 


100 


165 


100 


165 


150 


215 


100 


165 



£77,473 
34,284 
30.722 
2l,bl7 
21,372 
15,138 
15,138 
15,138 
14,693 
14,693 
14,693 
14,693 
19,146 
14,693 



£.^6,614 
25,054 
22,450 
15,943 
15.618 
11,063 
11,063 
11,063 
10,737 
10,737 
10.737 
10,737 
13,991 
10,737 



2,430 



3,635 



£323,693 £236,545 



£20,858 
9,230 
8,272 
5,874 
5,754 
4.075 
4,075 
4,075 
3,956 
3,956 
3,956 
3,956 
5,155 
3,956 



£37,148 



The ordinary shareholders will then receive 6 per cent., and the balance of the 
profits will then be divided evenly among all shareholders. It is also proposed ^'^ 
to make a reduction in the price of power to the mines holding capital in the 
company, 4s. 6d. per h. p. being charged to them as against 5s. to mines holding 



r 



PRODUCTION. 209 



no capital, and, further, a sliding scale of charges will be introduced whereby 
the largest consumer of energy will pay the smallest rate per h. p. 

By this arrangement the mine-owning shareholders will get their power: 
(i) at 30 per cent, of the present cost, (2) will be guaranteed 6 per ^ent. on the 
money invested in the company, and (3) will still further reduce the cost of 
power by receiving the balance of profits in dividends, which collectively will 
reduce the cost of power to half the present expense. The ordinary share- 
holders, on the other hand, will be guaranteed a sufficient number of customers 
to ensure the success of the undertaking. 

For the proper control of the company it is suggested that three mine 
managers represent the mine-owners' interests, while the other three directors 
will be appointed by the ordinary shareholders. It is further suggested that no 
director shall receive any remuneration until a dividend of at least 10 per cent, 
is declared. The method proposed for carrying out this scheme is to convey 
the electricity from the generating station at high pressure (2,000 volts) to sub- 
stations, placed in as close proximity to the various points where power is re- 
quired as practicable. Those sub-stations will be furnished with accumulators 
capable of supplying the whole energy called for, for at least an hour. The 
power will be then taken from the accumulators at a lower and safer pressure to 
the various motors and lighting circuits. 

The advantages of this method of distributing are: 

1. The transmission is effected over the principal distances with a com- 
paratively small main, and with small loss of pressure (about 2j^ per cent.). 

2. By the introduction of accumulators the pressure can be conveniently 
reduced to a perfectly safe point before being conveyed to the motor. 

3. It is possible to keep the lamp at a perfectly steady c. p., notwithstand- 
ing the variations in the motor circuits caused by starting and stopping. 

4. In th€ event of a breakdown in the generating machinery, the accu- 
mulators would act as a reserve for at least an hour, and so prevent a stoppage 
at the mines. 

5. As the load of power circuits is always of a fluctuating nature, the use 
of accumulators will enable the engines to work steadily at their most economical 
point, the fluctuations being taken up and given off by the batteries. 

6. That it is perfectly flexible in providing for variations in pressure for 
all purposes, as any pressure may be obtained from two to 2,000 volts, without any 
alteration to the existing arrangements, other than changing a wire. 

With reference to the compressed air system, it is found to be more eco- 
nomical to compress the air direct at the central station, and convey it by pipes 
to the various mines, rather than simply to supply power on the mines to drive 
the various compressors, as thereby the cost of plant would be greater and the 
losses of transformation heavier; but in order to economize in the outlay of pipes, 
and also to preserve a uniform pressure at the mines, it is proposed to transmit 
the air at 300-lb, pressure per square inch to receivers capable of storing 
energy for 200 drills for an hour, placed at the sub-stations, and then to reduce 
the pressure before entering the service-pipes to the mines, to the usual working 
presgure of 80 lbs. by means of reducing valves. 

Both the electric and compressed air energy will be measured by meter, 
BO that only the po\ver actually used will be charged for. 



2IO PRODUCTION. 

It is found in the Eastern colonies that a mine producing 5 dwt. of gold 
per ton crushed, can be made to pay dividends with care and economy, and while 
it would be rather rash to predict that the same state of economy would be 
arrived at here, by a saving in the cost of power, it is at all events safe to say 
that the introduction of the scheme just detailed would be a step in that direc- 
tion, and in some cases, might make the difference between a dividend-producing 
and a call-producing mine. 

This system has been introduced on the Rand in South Africa by two 
large companies with great advantage to themselves and to the mines utilizing 
the energy supplied by them, although the conditions there are not so favorable 
for economical running as in the Kalgoorlie goldfield, owing to the fact that the 
mines cover a much larger area, and the expense of labor is very much less. 

In America the same method of generating power has been adopted in the 
large mining centres with most successful results, while such methods also are 
finding favor in Great Britain and on the Continent, where circumstances allov/ 
of a central generating power. 

A machinery area has been secured adjoining the present railway (that 
will be an important consideration), in almost the centre of what is known as the 
gold-bearing belt, which embraces over fifty distinct companies or leases, nearly 
all of which have been proved payable mines, but will require power and light 
It is, therefore, almost certain that by the time the plant is erected the whole 
of the proposed power and light will be applied for, and in the near future a 
large extension will be necessary. 

There are at present a considerable number of mines that are in a forward 
state of development and will soon require machinery, and consequently they will 
be only too pleased to avail themselves of the proposed company's power, etc., 
if the scheme is carried out without delay. 

Should any of the plant now in use by any of the mines which propose 
to take power from the central station be found suitable, the company would be 
prepared to take it over at a fair valuation and utilize it in the central station. 

Letters expressing approval of and wishing success to the scheme have ij 
been received by Mr. Samuel Wilson from Mr. R. Hamilton, Great Boulder; Mr, 
T. Hewitson, Ivanhoe; Mr. William Dick, Golden Horseshoe, and the manager! 
of all the leading mines in this district. | 



REPORT ON TRIALS MADE AT MAGOG, QUEBEC, TO TEST THE 
ECONOMY EFFECTED BY PREHEATING COMPRESSED AIR. 



By Prof. J. T. Nicolson, D. Sc. (Edinburgh & McGill) M. Inst. C. E. 



These trials were made during the month of April, 1899, at the Dominion 
Cotton Mill, Magog, Canada, where there is installed a 150 horse-power hy- 
draulic air compressing plant on the system devised by C. H. Taylor, of Montreal. 

They were made at the instance of Mr. John A. Inslee, of St. Louis, and 
conducted under the auspices of Mr. Inslee, the Taylor Hydraulic Air Com- 
pressing Co., and the Dominion Cotton Mill Co., jointly, 



PRODUCTION. 211 

The trials were conducted by the undersigned, assisted by Professor R. J. 
Burley, B. Sc, etc., of McGill University, but a number of prominent engineers 
from the United States were invited to be present and took part in the experi- 
ments. Among others I may mention Mr. A. Langstaff Johnson, of Richmond, 
Va., Mr. Wm. O. Webber, of Boston, Mass., and Mr. John Birkinbine, of Phila- 
delphia, Pa. 

Experiments were made on five different methods of using compressed air 
in an ordinary steam engine of the Corliss type. 

ist. The air was supplied to the engine cold. 

2d. Steam was injected into the air in the main pipe before supplying it to 
the engine. 

3d. The air was injected among the water in a steam boiler and heated by 
mixing with the water and steam of the boiler before being supplied to the engine. 

4th. The air was blown upon the surface of the water in a steam boiler 
and heated, by mixing with steam in the same before being made to drive the 
engine. 

5th. The air was pass2d through a tubular heating vessel and heated by a 
coke fire, afterward being used to work the engine. 

For all the experiments the air was drawn at a pressure of 53 lbs. from the 
S-in. main air pipe of the Taylor Air Compressor, which supplies power to the 
mill, and was piped to a 12-in. diameter by 30-in. stroke Corliss engine, supplied 
for the purpose of the trials by the Laurie Engine Company, of Montreal. 

A friction brake was fitted on the fly-wheel of this engine and the engine 
in this way was worked up to its full power at about 75 revolutions per minute. 

Connection was made to a Lancashire boiler 7 ft. diameter by 30 ft. long 
when it was desired to mix steam with the air for purposes of pre-heating. 

When dry heating was resorted to the air pipe was led through a heater 
on its way to the engine, having been previously blanked off from the steam 
boiler. This heater was designed by the writer and built by Messrs. The Laurie 
Engine Co. for these experiments; but, as it was designed of such size as to heat 
the whole of the compressed air used in the mill, it was considerably larger than 
was required to heat the greatest quantity of air which could be used by the Cor- 
liss engine employed on the test. It was, therefore, a matter of some difficulty 
to prevent the heater and the tmall quantity of air passed through the same from 
becoming hotter than was desired. 

For the experiments made without pre-heating, the observations made were 
as follows: 

The temperature of the air before entering the engine. 

The same on leaving the engine. 

The pressure of the entering air, indicator cards from each end of the 
cylinder, readings of. the revolution counter and of the rope brake weights. 

A trial was conducted \Aith cold air on April 27th, in the presence of Mr. 
Birkinbine, which gave the following results: 

The air entered at 66.5 F. and was exhausted at — 41 F., the revolutions 
being 74.6 and the cut-off about one-third of the stroke. The indicated horse- 
power was 27 and the weight of air used per hour was 1,671 lbs. This gives 
about 841 cubic feet of free air at 60 F. per I. H. P. hour. 



212 PRODUCTION. 

On another trial made under same conditions 850 cu. ft. of free air were 
used per I. H. P. hour. 

2. In the case of experiments made with the dry heating, the following 
observations were made : 

The temperature of the air before entering the heater; after passing up 
the first row of tubes ; upon .leaving the heater ; before entering the engine. 

The temperature of the furnace and flue gases of the heater were also 
taken, the former with a Callendar's patent electrical promoter. 

The amount of coke (Sherbrooke gas coke) used was carefully weighed 
and the trial only began when the conditions had become steady, i. e., about three 
hours from the time of beginning the run with heated air. Cards were taken ; 
the brake horse-power and the revolutions were also observed. 

With air entering the heater at a pressure of 53^^ lbs. gauge and at a 
temperature of 58.2 F., it was raised to 225 F. after passing the first row of tubes, 
and to 363 F. upon leaving the heater. Owing to undue length of air pipe and 
lack of proper covering, the air fell in temperature to 287 F. before entering the 
engine. It was exhausted at 88 F, and the pressure at the engine was 52^^ lbs. 
by gauge. 

The temperature of the gases leaving the fire was only about 700 F. — and 
was reduced to 100 F. in the flue of the heater. It was difficult to use a small 
enough quantity of coke in such a large heater without letting the fire out alto- 
gether. A closed ash pit was used and the air for combustion supplied from the 
compressed air main and couid be regulated in its amount to a nicety. 

Under these conditions and with exactly the same cut-off as in trial of 
cold air, the indicated horse-DCwer being 26.7 and the revolutions 70 per minute, 
there were used 1,310 lbs. of air per hour, this gives a consumption of 640 cu. ft. 
of air per I. H. P. per hour, a reduction of 850 — 640 — 210 cu. ft. of free air per 
I. H. P. per hour due to pre-heating. Thus 210-850, a saving of 24.7 per cent, is 
effected in the quantity of air used. 

This saving was effected by the burning of 9.3 lbs. of coke per hour, or of 
9.3-26.7 348 lbs. per H. P. per hour. 

These results may be stated otherwise as follows: • 

To produce 100 H. P. with cold air, 85,000 cu. ft. of air were required in 
this engine; when pre-heated to 287 F., the horse-power yielded was 85,000—640— 

9.3x133 

133 H. P., and as this heating was effected by the burning of ^y i^s. 

27 
of coke per hour ; the additional ^3 H. P. were obtained by an expenditure of 

47 
47 lbs. of coke per hour, or at the rate of — 1.42 lbs. of coke per hour additional. 

33 
If we assume that this gas coke had ^ of the calorific value of good coal, 
it is seen that wc obtained an additional horse-power for every (i.42x.>4) i lb. of 
coal burnt in the heater. 

As an ordinary steam engine and boiler of this size would require from 4 
to 8 lbs. of good coal per H. P. per hour, it is seen what a very economical mode 
of using the heat this is. Heat is used 4 to 8 times as efficiently in a compressed 
air prc-heater as it is in a steam engine and boiler, 



PRODUCTION. 213 

With regard to the resuhs of this trial it ought to be remarked that a large 
radiation loss per lb. of air used was taking place, both on account of the undue 
size of the heater and on account of its distance from the engine. Much more 
favorable results can be and in fact, have been obtained, when the size of the 
engine and heater are properly proportioned. 

Professors Riedler and Guttermuth have obtained an additional horse- 
power in air motors for every ^-Ib. of coal burnt to heat the air: This is an 
economy far surpassing that of any prime motor in existence. 

In large plants with first-class air motors, where double or triple pre- 
heating might be resorted to, a better result than even this can easily be obtained. 

In a large transmission plant consisting of a Taylor Air Compressor, a 
five-mile pipe line, air engines and electric generators, with coke pre-heating 
stoves, the full or gross power of the water fall can be obtained at the terminals 
of the dynamo, at a comparatively insignificant cost for fuel. 

No other system of energy transmission can compare with this for economy 
of first cost and maintenance. 

3. Tests were made of the economy to be obtained by heating the air 
by mixing it with steam from a boiler before allowing it to do work in the engine. 
• The results are of the highest scientific interest, and show the adaptability 
of compressed air to almost any condition of employment. As regards economy, 
this method is, however, inferior to that of dry heating. By mixing from 10 to 
13 lbs. of steam per H. P. with the air, the quantity of air required was reduced 
from 850 cu. ft. to 300 to 500 cu. ft. per I. H. P. per hour. Thus the air required 
for a 100 H. P. engine running with cold air would be sufficient to operate an en- 
gine of 85,000 — 400-^210 H. P. if mixed with 12^x100 — 1,250 lbs. of steam per 
hour. This can be supplied by about 140 lbs. of coal per hour; so that no H. P. 
additional were obtained by the burning of 140 lbs. of coal or 140 — no — 1.3 lbs. 
of coal per I. H. P. per hour additional 

Such a method of heating, economical as it may appear, would, however, 
be unsuitable except for powers of over 50 H. P., unless waste steam is available 
from a boiler plant at times of low demand. 



COMPRESSED AIR AND ITS DISTRIBUTION FOR POWER PUR- 
POSES IN THE CITY OF PARIS; HOW IT IS PRODUCED, 
ITS NUMEROUS APPLICATIONS AND ITS COST. 



I?Y M. VICTOR I'OPr 



HISTORY OF THE ENTERPRISE. 

The world renowned compressed air system for power purposes which is 
now in operation in Paris was started in a very small and modest way. Its point 
of departure was the installation of a small compressed air plant in 1879. This 
plant was installed in the basement of a dwelling house situated at No. 7 St. 
Anne street with a view of supplying compressed air to a small circuit for the 



214 PRODUCTION. 

operation of pneumatic clocks, and this was the first application of compressed air 
for this purpose. The machinery which was installed at that time consisted of 
two small steam actuated air compressors of 6 h. p. each. 

The receivers, pressure regulators, standard clock controlling all the pneu- 
matic clocks and other apparatus consistent with the plant were installed on the 
ground floor; the main standard clock controlling all the pneumatic clocks on the 
compressed air circuit, which was at that time about three miles long, gave each 
pneumatic clock a compressed air impulse every minute moving the minute hand 
1-60 of a revolution. In addition to these clocks, which were placed on the 
principal thoroughfares, and the results being so satisfactory, a large number 
of them were installed soon after the beginning of operations in a number of 
public buildings and private houses. 

In 1898 the compressed air installations of the Popp System comprised the 
following : 

I St. — One compressed air central plant of 8,000 h. p., situated on the Quai 
de la Gare. 

2d. — One central station for the operation of pneumatic clocks. 

3d. — One main pipe line, having a total length of 138 miles, this pipe line 
being placed underground and located in a tunnel. Of these 138 miles of m^n 
pipe line 41 miles are operating the pneumatic clock service and 97 miles are for 
the supplying of compressed air for power purposes. In addition to the main 
pipe line, there are over 20 miles of branches. These branches conduct the com- 
pressed air to 955 power consumers and to 1,637 establishments in which com- 
pressed air is used for the operation of pneumatic clocks. 

4th. — Compressed air furnished to consumers operate 1,600 h. p. of engines; 
is used in addition for 163 other purposes than power, and in addition, there are 
180 passenger and freight elevators all operated by means of compressed air. 

5th. — The company owns and operates 7,000 pneumatic clocks. As will be 
seen, great progress has been made since the installation of the small plant in 
St. Anne street. 

QUALITIES OF COMPRESSED AIR. 

The report of Mr. Humblot, General Inspector of Public Works in Paris, 
contains the following: "There is no reason why power could not be transmitted 
by means of compressed air, and the theoretical considerations on the subject 
have the tendency to give compressed air the preference above any other method 
of transmitting power. Compressed air is not a source of power, it is only a 
medium for the transportation of heat, which heat can be retransformed into 
power. Thus there is a great difference between this kind of power transmission 
and other methods such as the transmission and transportation of power by 
means of water or electricity. Water is' nothing but a purely mechanical medium 
between the piston of the pump supplying same and the piston of the motor 
operated by same. It can be compared to a solid incompressible rod connecting 
two mechanical organs. Such manner of transmitting power presents many 
inconveniences and losses, and in no case can the power obtained by the motor 
operated by same be superior to the original power. 

"Electricity is a form of energy, same as heat, and can be transformed into 
mechanical work, but here again the amount of power obtained at the further end 



PRODUCTION. 



215 



^f the line is always inferior to the power supplied at the starting point. As an 
lectric conduit can receive nothing but electricity, the loss between starting 
)int and final point must be made up by means of electricity, if such loss is made 
fp. Now, in order to produce electric power heat has to be first produced; this 
;at transformed into mechanical work; mechanical work into electricity, and it 
evident that this combination of transformations is inferior to a system which 
lows the making up of losses direct by the addition of heat, as can be done with 
impressed air. In order to fully understand the principles of distributing 




FIG. 62. — BOILER ROOM OF THE PARIS PLANT. 



compressed air, it is necessary to know the fundamental principles of the 
mechanical theory of heat and which are as follows : 

"Any production of heat corresponds to the destruction of a power; any 
production of power corresponds to the absorption or destruction of a certain 
amount of heat. 

"The unit of energy is the kilogrammetre, which represents the power 
necessary to elevate one kilogramme one metre in one second. The unit of heat 
is the calorie, and represents the necessary quantity of heat to elevate the tem- 
perature of I kilogramme of water i** cent. This corresponds to the elevation of 
temperature of 4° cent, for i kilogramme of air. The absorption or suppression 
of one calorie corresponds always to 425 kilogrammetres of mechanical work 
produced; the absorption' of 425 kilogrammetres of mechanical work corresponds 
always to the omission of one calorie. 



2i6 PRODUCTION. 

"The above statement does not always exist in practice, and the role of the 
engineer consists in producing the above transformations from heat into work, 
and vice versa, with the least possible loss. 

"Should this be obtainable in practice, the efficiency of compressed air 
apparatus would be lOO per cent. 

"Example — One kilogramme of coal represents practically 5,000 calories; 
with 900 grammes of coal a steam engine will produce practically one h.-p. during 
one hour, the one h.-p. being equal to 75 kilogrammetres. As the hour is equal to 

3.600 seconds, we can sav — — — =635 calories, and then — ^7— =14 per cent. 

425 ^^ 5,oooX.9 

"It is well known that 800 calories are lost through the smokestack; that 
600 calories are absorbed in condensation, and that the balance of the loss comes 
from radiation and absorption in general. Thus we are in a position to say that 
for the present, and until better apparatus for the generation of heat and steam 
are produced, the steam engine in its present condition has reached an almost 
perfect stage; but, notwithstanding its low effectiveness of 14 per cent., it is at 
present the only method of obtaining primary power. For air, however, we are 
confronted with a different problem. Air must be considered only as a reser- 
voir for heat and a vehicle capable of transporting same. When air is com- 
pressed it forms a resistance, it absorbs power, and consequently it increases in 
temperature. When this air, after being compressed, regains atmospheric pres- 
sure through expansion and mechanical work performed, its temperature will 
be decreased. 

"Suppose that air, after being compressed, would not lose any of its heat 
between the compressor and the place where it is used; that there would be no 
loss by friction or leakage ; that the number of calories absorbed by the com- 
pressor and the number of calories lost during the work of expansion would be 
equal, then the efficiency of the air compressor would be 100 per cent. This does 
not take friction of compressor into consideration. It cannot be obtained in 
piactice, as we do not allow the air to absorb all the heat produced during com- 
pression. If this were done, the air would lose its heat by absorption and radia- 
tion in the pipe line and would decrease in volume and pressure. Excess of heat 
produced during compression is absorbed either by water injection or by water 
jacket circulation during the process of compression, and each calorie absorbed 
by the water corresponds to a loss of 425 kilogrammetres in the receiver, or an 
equivalent loss in weight of compressed air. 

"According to Pernolet, the amount of heat produced by compression and 
which should be absorbed during the process of compression is as follows : 

For two atmospheres — 14 calories. 

For three atmospheres — 23 calories. 

For ^our atmospheres — 29 calories. 

For five atmospheres — 34 calories. 

For six atmospheres — 38 calories. 

For seven atmospheres — 41 calories. 

"Suppose that we use water at 15 degrees cent., and, furthermore, that 
the water would be discharged at 30° cent., each kilogramme of water would 
absorb 15 calories, and for a pressure of seven atmospheres we would require 2.7 
kilogrammes of water per kilogramme of air admitted to air cylinder. 



PRODUCTION. 217 

"It will be seen later that one h.-p. being able to handle eleven kilogrammes 
of air, the practice and theory will agree. Thus, per nominal h.-p. of a steam 
engine, the amount of water required will be 2.7 X 11 X 15 = 445 calories. 

"In addition to the above loss of power during compression, there are sev- 
eral others which are secondary •. 

"ist. — The contraction of t|ie air, which will be discharged at 30** cent, 
into the receiver and which will cool to 15° cent, in the main pipe line on account 
of radiation and absorption. This loss for 11 kilogrammes of air per h.-p. will 

he equal to — — =41 calories. 

"2d. — A certain amount of vapor remains in the compressed air and is car- 
ried with same into the pipe line. The quantity of vapor is hard to determine. 
We can, however, count on about 10 grammes of water per cubic metre of air 
at atmospheric pressure; this corresponding to about 100 grammes per h.-p., or, 
in other words, 61 calories. 

"3d. — The quantity of water required for cooling, either by means of injec- 
tion or otherwise, reduces the volume or capacity of the air cylinder. This is, 
however, of no consequence, principally when we consider that the injection 
water reduces the clearance to a minimum. Thus, we can say that the total 
loss of heat between the compressor and the terminal point of pipe line amounts 
to 445 -f- 41 + 61 == 547 calories. As we have used 635 calories to compress 
the air and have a loss of 547 calories during compressfon, etc., we can deliver 
only 88 calories to the engine or other apparatus at the further end of the pipe 
line. We know, however, that compressed air is a valuable receptacle for calories 
and that it will give them up when required to produce mechanical work, we can 
add calories to produce compressed air, and these calories will be given 
up and transformed into mechanical power or energy in addition to the 
original calories stored in the compressed air. Practice has proved that 
compressed air will lose 65° cent, for a reduction in pressure of six atmos- 
pheres. Theory will bring the figures to 90° cent. We have thus for each 

kilogramme of air a reserve of -^^-^^!^^ — ^ =20 calories, and as each h.-p. handles 

4 

II kilogrammes of air the number of calories stored would be 220. Adding to 
this the 88 calories added by the work of compression, we find that i h. p. of 
compressed air will amount to 308 calories at end of pipe line; thus, using 635 
calories to do the work of compression, and obtaining 308 calories in work, the 
practical percentage of efficiency of the air compressor would be 48.6 per cent. 
If we consider, however, that the difference between the indicated and nominal 
h-p. amounts generally to about 18 per cent., this loss being due to leakage, fric- 
tion, dead-load of the engine, etc., for the steam engine itself, and that the air 
leakages in the air pipe line amount to about 5 per cent., we can only count on a 
practical efficiency of 37 per cent. 

"This result being obtained without taking reheating into consideration. 

"Practical tests made by a commission appointed by the Ministry of War 
have demonstrated that four 450 h.-p. air compressors have absorbed 38,000 kilo- 
grammes of free air and have produced 16,000 kilogrammes of compressed air. 
The tests being made on short pipe lines without any leakages whatever, it will 



2l8 



PRODUCTION. 



be seen that the practice agrees nearly with the theory, the effectiveness of the 
tests giving a result of 42 per cent., while the theory above mentioned should 
have called upon an effectiveness of 48.6 per cent. 

"The difference between theory and practice is thus only 6 per cent. As 
air is a proper receptacle for the absorption and storage of calories at any stage 
during the compression before being used for power purposes, it is a very im- 




FIG. 63. — AIR COMPRESSORS AND AIR STORAGE RESERVOIRS, 



portant subject to study as to how a certain number of calories can be given to 
the air after compression in order to make up for all the loss due to cooling, 
leakage, etc. There is no limit to the number of calories which can be added to 
the air except that a too high elevation of temperature wants to be avoided, as it 
would prove either inconvenient or dangerous. We have seen above that there 
are only 88 calories out of 635 available during expansion at the terminal point. 



PRODUCTION. 219 

Thus, in order to obtain 100 per cent, of power we ought to restitute 547 calories 
per indicated h. p. Should we figure on nominal h. p. we should add about 20 
per cent. 

"This would bring the total number of calories required per nominal h. p. 
to 762. Now, having seen that 11 kilogrammes of compressed air will store 88 
calories, or in other words, 8 calories per kilogramme, let us see in practice how 
many calories we can add to each kilogramme of compressed air by means of 
heat either in one, two or three stages before and during the work of expansion. 
It is easy while expanding to reduce the temperature of air 150° cent, (with 
two expansions, a decrease of 300° cent.) This decrease in temperature can be 
obtained while expanding the air in two cylinders, increasing its temperature 150° 
before letting it enter each cylinder. The total loss of temperature being 300° it 
represents a loss of 75 calories per kilogramme of air, which, added to the 8 
calories which the air was ready to give up ordinarily, the total number of 
calories absorbed will be 83. 

"We have said above that one kilogramme of coal represents S,ooo calories, 
and that to consume this coal, we have to lose 16 cubic metres of air at 400° 
m the smokestack, this being equivalent to 1,600 calories, the loss will be 32 per' 
cent. In order to obtain the 5,000 calories with one kilogramme of coal, we will 
have to add 246/1,000 kilogramme of coal. Theory has demonstrated that the 
efficiency without reheating amounted to Z7 per cent., thus it will be seen that 
for i/io of a kilogramme of coal consumed at the central power plant and 
246/1,000 used for reheating at the terminal point one effective h. p. of com 
pressed air can be obtained and a decrease of temperature at 300° cent, will be 
effected. Should the increase in heat furnished by reheating amount to only 150° 
cent., a larger amount of coal in reheating would be necessary. Tests which 
have been made confirm positively the above statement, and it is a remarkable 
proof that the hot air motor is a perfect thermic engine, where theory and prac- 
tice differ the least. 

"It is well known by all technical engineers that hot air engines are ma- 
chines which show the best results theoretically, and that if these machines are 
not used in greater number it is on account of their complications in construction 
All the hot air engines are based on the following principle, which is to intro- 
duce a certain number f:f calories under the piston of the engine and then 
transform the heat into mechanical work by either of the two following pro- 
cesses : 

"ist. The compression of air in the machine itself in order to expand 
same later on. 

"2d. Direct expansion of heated air, using the power obtained direct on 
the crank. 

"The above operations are explained by the following formula: The 
calories which are transformed into mechanical work are equal to the work of 
compression plus the work on the crank. The sum of these two energies, i. e., 
compression and power, which can be used, require a great number of calories, 
or, in other words, a great amount of energy on the piston of the engine; this 
piston, presenting only a small surface, is subject to great strains and also to 
deterioration on account of the great amount of heat prevalent. 



220 PRODUCTION. 

"Thus it will be seen that the ideal is to compress the air in a different 
machine than the one which is used for producing the power, and for this pur- 
pose central compressed air power plants prove to be the best adapted where 
compressed air power can be obtained and produced cheaply, and then the con- 





FJ(;. 64. — PLACE DE LA REPUBLIQUE, PARIS, SHOWING THE COMPKESSEU AIR MAIN 

PIPE LINE. 

sumer needs only to attend to the reheating, which amounts to very little regard- 
ing expense and attendance. 

"To obtain a nominal horse-power at the end of the pipe line we have to 
use 1.50 kilogramme of coal, of whoch 900 grammes are used at the central sta- 
tion and 250 grammes at the terminal point for reheating. This gives us an 
cflficiency of 78 per cent., and is under all conditions superior to the best results 
obtained by electrical power transmission. 



PRODUCTION. 221 

"4th. The installation of a compressed air central power plant for distri- 
bution comprises : 

"ist. One central power plant, comprising air compressors, boilers or 
other power medimn, receivers, pressure regulators, etc. 

"2d. A complete endless main pipe line starting from the central power 
station and returning to same. From this air pipe line a certain number of 
branch pipes run for the distribution of compressed air to the consumers; these 
branches furnished with automatic water traps in order to eliminate the con- 
densed water. 

"3d. Air meters placed at every outlet for measuring the amount of air 
used by every consumer, these meters varying to suit pipes from ^/i inch to 3 
inches in diameter. 

"4th. Apparatus for charging the receivers of compressed air cars or 
tramways, together with reh eaters and all appurtenances connected with same," 

CENTRAL POWER PLANT (QUAI DE LA GARe), ESTABLISHED IN 189I. 

This is the most important central power plant not only in Paris, but in 
the whole world. The plant is installed and built of such size as to have an 
ultimate capacity of 24,000 h. p. The outlay is arranged for the installation of 
three rows of air compressors, each row amounting to 8,000 h. p. and com- 
prising four 2,000 h. p. air compressors; thus the complete installation com- 
prises twelve 2,000 h. p. air compressors. 

The first row of 8,000 h. p., which has been in operation since 1891, consists 
of four 2,000 h. p. air conipressors of the triple expansion Corliss type for the 
steam end, the weight of these four machines being 1,800,000 kilos, practically 
4,000,000 lbs. 

Each of the low pressure steam cylinders weighs 30,000 kilogrammes 
(66,00 lbs.). 

The boilers are of the water tube type furnished with economizers, five 
for each compressor, thus making a total of twenty. 

The four compressors are fitted with positive air inlet and outlet, and are 
of the three-cylinder type; two low pressure cylinders of same size fitted with 
intermediate receivers and intercoolers and one high pressure cylinder. That 
means the air compression is done in two stages. In addition to the above, pan 
of the cooling is done during the period of compression by means of water 
injection in the cylinders. 

The compressors are of the tandem vertical type, with three cranks set- 
ting at 120°, the steam cylinders being placed directly below the air cylinders. 

The total height of each air compressor is 12^5 meters (40 feet). 

The steam ends of the compressors are of the triple expansion type and 
are controlled for the low and intermediate cylinders by means of variable cut- 
ofT Corliss valves, with trip motion, while the high pressure cylinder, which is 
fitted with the same kind of valves, is controlled by an automatic combined air 
pressure and speed governor in addition to a quick acting variable liand gov- 
ernor; this in order to stop the racing or running away of any air compressor 
and to control its speed and output at a steady working pressure of 8 kilo- 
grammes (i. e., i?o lbs.). 



222 



PRODUCTION. 



These different methods of governing and controlling speed and pressure, 
and which are each independent of the other, act all on the steam distribution of 
the high pressure cylinder. 

The valve motion for the air cylinders is actuated through a system of spur 
gears placed on the main shaft; each compressor is fitted with two heavy fly- 
wheels and the shafts of the four engines which are placed in line are con- 




FIG. 65. — UNDERGROUND PIPES OF THE PARIS PLANT. 



nected together with clutch couplings, thus allowing them all to work in unison. 
The four engines are besides rigidly tied together by means of heavy cast iron 
bed plates, thus insuring perfect alignment, the upper ends of frames being also 
tied together with heavy tie rods. 

Access is given to all parts of the machines through four staircases and 
platforms extending the full length and on both sides of the four compressors. 

The condensers, air pumps and water pumps are placed in pits next to the 
engines, these pits being 12 feet deep and reached by means of wrought iron 
stairs. Each compressor has its own condenser, air pump and water pump, the 



r 



PRODUCTION. 223 



pumps being actuated directly from the crosshead of the high pressure cylinder 
through a beam controlled by same. The air valves of the two low pressure 
cylinders are of the positive inlet type and are fitted with rubber lined seats; 
the outlet valves are also of the same type, and it has been found that for low 
pressure cylinders these valves give very good results and dispense with shocks 
and jumping. 

The two low pressure air cylinders are supplied with air direct from the 
atmosphere, discharging same into the combined receiver and intercoolers, which 
are placed on heavy cast iron columns; these receivers supply the air to the high 
pressure cylinder, where it completes its compression and is discharged into the 
terminal receivers. 

In order to insure the best results it has been decided to admit the air for 
supplying the two low pressure cylinders direct from the atmosphere and passing 
through small longitudinal openings whereby this air will give up part of its heat 
and moisture. 

Direct steam actuated fly-wheel pumps, entirely independent of the air 
compressors, furnish the injection and jacket cooling water for the compressors. 
In addition, these pumps furnish water for cooling the compressed air in the 
intercoolers between high and low pressure cylinders and in the high pressure 
receivers. 

The drawings and sketches accompanying this article will give the reader 
a fair idea of the general arrangement of the plant and a conception of the 
provision made for future increase. The engines have been built for extra 
heavy duty and are amply strong in all their parts to develop much more power 
than required. All working parts, such as piston rods, crank pins, crosshead 
pins, etc., are made of hard crucible steel and removable. Main bearings, crank 
and crosshead pin bearings, valve rod pin bearings, etc., are fitted with adjustable, 
removable bronze quarter boxes. 

Up to this date, after eight years of steady Avork, both day and night, it 
has not been found necessary to renew any of the working parts of any of the 
air compressors except the rescraping and regular readjusting incidental to gen- 
eral wear and tear. 

All the engines run at a regular speed of 60 revolutions per minute, but 
the combined air and steam governors allow this speed to be increased to 72 
revolutions if required. 

The amount of air handled per hour by the four machines now in operation 
(8,000 h. p.), and which is compressed to 8 kilogrammes per square centimetre 
(i. e., 120 lbs. per square inch) amounts to 70,000 cubic metres (220,000 cubic 
feet) per minute. The above is based on a temperature of 60** F, and a barome- 
tric pressure of 29 inches. 

Each of the 2,000 h. p. air compressors delivers its supply of compressed 
air at 8 atmospheres into two high pressure air receivers of 30 cubic metres 
capacity (i. e., 1,000 cubic feet each), from which it is distributed to the central 
main pipe line of 500 milimetres diameter (i. c, 20 inches diameter). 

The boilers are of the water tube type manufactured by the Babcock & 
Wilcox Company, tested at 250 lbs. to the square inch, and furnish steam to the 
engines at 150 lbs. pressure. Each set of boilers is furnished with a steam 
rpheater controlled in such a manner as to allow the steam from the boilers to 



224 PRODUCTION. 

pass through or around same. All steam pipes are installed in duplicates, thus 
allowing any engine or boiler to be put in or out of commission and to allow 
the cutting out of either of the main steam pipe nnes in case of accident without 
interfering in any way with the operation of the plant. 

Boilers to the number of 20 (i. e., 5 for each engine) are as follows : 

Number of vertical sections for each boiler 12 

Number of tubes per section 9 

Number of tubes per boiler 108 

Number of tubes — 5.4 metres — equal 18 ft. 

Diameter of tubes 4 in. 

Heating surface for each boiler, 182 sq. metres, equal about 2,000 sq. ft. 

Heating surface of economizers for the complete battery of boilers — 

500 sq. metres — equal 6,000 sq. ft. 

Engines and air compressors are as follows : 

Nominal h. p. of each engine 2,000 h. p. 

Number of revolutions per minute 60 

Pressure of compressed air in receivers, S kilogrammes 120 lbs. 

Boiler pressure per sq. in., 12 atmospheres 180 lbs. 

Diameter of high-pressure steam cylinder 36 in. 

Diameter of intermediate steam cylinder 50 in. 

Diameter of low-pressure steam cylinder 80 in. 

Diameter of the two low-pressure air cylinders 44 in. 

Diameter of high-pressure air cylinder 34 in. 

Stroke of all the pistons 56 in. 

Diameter of fly-wheels 18 ft. 

Diameter of air pump 40 in. 

Stroke of air pump 24 in. 

Diameters of intercoolers and receivers 66 in. 

Length of intercoolers 36 ft. 

The following tests on the distribution of Compressed Air through main 
pipe lines have been made in Paris. 

LOSS OF AIR. 

The loss or decrease in pressure of compressed air in main pipe lines is 
due to either or both of the following causes : The loss in weight of air caused on 
account of leakage and the loss in pressure due to friction. Both of the above 
are of great importance and should be taken into consideration. The leakages, 
if properly attended to in due time, and if the main pipe line is kept fairly tight, 
do not require much attention as it is the duty and to the interest of any central 
compressed air power plant engineer to reduce them to a minimum. They remain 
a constant factor of loss in amount of air furnished. 

The loss of compressed air through leakage is about proportional to the 
number of fittings, such as T's, elbows and valves installed on the main pipe line, 
and that it amounts to about 6 per 'cent, of the total capacity of the plant. As 
this is a constant percentage of loss for an even pressure, it will be readily seen 
that if the plant were of 24,000 H. P. capacity, the total loss of compressed air 
would be onljy 2 per cent., it being 6 per cent, for 8,000 H. P. 



PRODUCTION. 



225 



LOSS OR REDUCTION OF PRESSURE DUE TO FRICTION IN THE MAIN PIPE LINE. 

The reduction in pressure due to friction is a question of the greatest 
importance, and in order to determine same and to avoid its being excessive, it 
is well for the owners of the central power plant to thoroughly investigate the 
following results. 

A great many experts had formed an opinion that loss due to friction 
would not amount to much, and Mr. Arson's experiments had led the company 
to believe that the loss would be very small, but all these experiments and tests 




FIG. 66. — HOUR SERVICE — CENTRAL CLOCK IN ITS CABINET. 



were made with compressed air at low pressure and consequently low density. 
The company, however, decided to satisfy itself thoroughly, and engaged Prof. 
Gutermuth to make thorough tests, which were always made at night and on 
Sundays, when the traffic and supply were practically steady. These tests have 
proved that extraordinary loss of pressure was due to short bends, principally in 
the smaller branch pipe lines running uphill, notwithstanding the large diameter 
of 12 inches and the great number of receivers and automatic water traps con- 
nected with same. Thus it was decided to make thorough tests to determine the 
loss of pressure due to the receivers placed in pipes, and then in the main and 
branch pipes between the receivers. The table pnl)lishod l)elow gives the results 
obtained. 



226 



PRODUCTION. 



LOSS OF AIR PRESSURE DUE TO FRICTION FOR ONE RECEIVER. 



Pressure 

at entrance 

of 

receiver. 


Pressure 
at outlet 

of 
receiver. 


92.84 lbs. 
92.36 " 
7174 " 


91.87 lbs 
91.28 " 
69.23 " 


95.25 " 
90.11 " 


93.05 " 
89.08 " 



Loss. 
0.97 lbs. 
1.08 " 
2.51 " 
2.20 " 
1.03 " 



Averaf^e 

speed of air 

per second 

through pipes. 

19.8 feet. 

19.1 *' 

28.7 " 

24.4 " 

18.5 " 



The figures show positively that for each receiver there is a loss of 15 per 
cent, of one atmosphere when the speed of air amounts to seven metres (23 feet 
per second), and that for 9 metres (30 feet per second), the loss due to friction 
amounts to 0.2 of one atmosphere. Thus it will be seen that five receivers placed 
one behind the other will cause a decrease of pressure of one atmosphere. 

Twenty-three automatic water traps which were installed at different places 
on the main pipe line, did not result in any perceptible loss of pressure. The 
following table giving the number of tests and mentioning the places where they 
were made, will give the reader a fair idea of results to which reference has been 
made. 

TABLE 19. 

EXPERIMENTS IN DIFFERENT CONDUITS USED FOR THE TRANSMISSION OF AIR TO 
DETERMINE THEIR RESISTANCE. 



SECTION OF CONDUIT 



OS 



Total length from the Central Station at Saint Fargeau across the City and return 

From the Central Station to rue Fountaine au Roi , 

From Central Station to rue de Charonne 

From Place de la Concorde to Saint Fargeau 

From Station at Saint Fargeau to rue Fountaine au Roi 

From Station at Saint Fargeau to Place de la Republique. , 

Isolated tests conduits of different lengths | 

From rue de Charonne to rue Fountaine au Roi , 

From rue de Charonne to Saint Fargeau 



10.28 
8.15 
7.50 
5.75 
2.08 
1.066 
0.445 
4.57 
5.44 
2.74 



h' 



The above table relates only to tests made at nighjt while the distribution of 
air was practically at a standstill, and the whole compressed air plant at the 
disposal of the engineers in charge of the tests. Some tests, however, have been 
made while the plant was in full operation and while the compressed air reached 
the endless main pipe line experimented upon through both ends. The experi- 
ments were made at a place situated respectively four and five miles from the cen- 
tral power plant, and all readings were automatically registered by automatic 
recording pressure gauges placed at convenient places. All tests were thus made 
on a main pipe line having a total length of nine and one-half miles and fitted 
with four air receivers, twenty-three automatic water traps and forty-two gate 
valves. The resistance or loss ot pressure was made under different speeds of 
compressed air varying from zero to 50 feet per second. 



PRODUCTION. 227 

I desire to emphasize that in the main pipe line of Saint Fargeau — Fontaine 
au Roe — which does not contain any receivers, it has been demonstrated practi- 
cally that with a speed of 6% metres (203/^ feet per second), the loss due to 
friction amounts to 0.05 atmosphere per kilometre (3,300 feet) of main pipe line. 

Thus admitting that the original speed of the air be 6V2 metres (i. e., 20]^ 
per second), and the original pressure 14.7 pounds above the atmosphere, a main 
pipe line of 20 kilometres length (i. e., 66,000 feet) would not be adequate to 
transmit any power. 

A series of tests made on the main pipe line in Paris over a length of i6y^ 
kilometres (i. e., S5,ooo feet), with an average air speed of six metres (i. e., 20 
feet per second), has demonstrated that the loss due to friction amounts to 0.07 
of one atmosphere per kilometre. Thus, it is clearly proved that the forty-two 
gate valves, the twenty-three water traps and the four receivers do not represent 
a great percentage of loss and taking as a basis that any air pipe line will be 
fitted with about the same number of syphons, receivers, valves and traps as the 




FIG. 67. — COMPRESSED AIR MUNICIPAL CLOCK. 

above-mentioned line, it will be seen that a total length of main pipe of 14 kilo- 
metres (i. e., 46,500 feet) will produce the loss of one atmosphere. This result 
is the best obtained up to this time for such a length of main pipe line. 

In addition to the above, it has not been mentioned that the main pipe lines 
in Paris contain a certain number of elbows and grades, which certainly increase 
the loss of friction to a certain extent. The tests having been made under differ- 
ent air pressures, it has been found that the practical loss of pressure due to fric- 
tion does not proportionately increase with the pressure or with the density of the 
compressed air at least up to 60 pounds above the atmosphere, but it is demon- 
strated that in order to reduce the loss of pressure due to friction to a minimum, 
it is best to carry a high air pressure. 

Several installations which have given very good results are transmitting 
compressed air at various pressures of from 30 to 50 atmospheres, and in one 
case 160 citmospheres. The mechanical work necessary for compressing to high 



228 



PRODUCTION. 



pressures is in proportion to the increase of pressure ; for instance, the mechanical 
work required to compress air from ten to twenty atmospheres, represents only 
30 per cent, of the total mechanical work required to obtain the result. 

It is thus possible to produce high pressure compressed air at 2. small cost, 
to convey same for long distances through small main pipe lines with less loss of 
pressure than if the pressure was low, and this can be done with less loss of 
power than any other motive power, such as water or electric power transmis- 
sion. The transformation from high into low pressure for the operation of 
motors is effected without any difficulty at the place where the power is used, 




FIG. 68. — APPARATUS 



FOR THE DISTRIBUTION OF TIME SERVICE. POPP SYSTEM. 



this being done by an automatic pressure reducing valve. We will not, however, 
discuss here the very high pressure system, but confine ourselves to the medium 
pressure system, which is in practical use in Paris. The loss of pressure due to 
friction being one atmosphere for 14 kilometres (i. e., 46,500 feet), it will be 
easy to determine the loss due to friction in very long main pipe lines. As the 
resistance or loss of pressure due to friction decreases when the size of the main 
pipe line is increased, theory and practice have demonstrated that for doubling 
the diameter of the main pipe line and conveying the same amount of air at the 
sarne pressure through the larger pipe, the loss of one atmosphere would corres- 
pond to a length of a1)out 40 kilometres (i. c., 132,000 feet) ; or, in other words, 
should the main pipe line be 100 kilometres long (330,000 feet), the pressure at 



I>R0DUCT10N. ' 



2:^9 



the central station seven and one-half atmospheres, and the loss due to pressure 
one-half atmosphere, there would be a total loss of 7 per cent, between the central 
power station and the end of the pipe line. 

Other experiments have decidedly demonstrated that a main air pipe line 
of 600 milimetres diameter (i. e., 24 inches), will be commercially fitted to trans- 
mit 24,000 H. P. without excessive :loss, and it has been furthermore established 
that if transmission of power exceed 40 kilometres (i. e., 25 miles), compressed 
air will be a better medium than water or electricity. 

COMPRESSED AIR MOTORS. 

In order to utilize the full power accumulated in compressed air and to 
obtain all the energy possible, it is found necessary to reheat the compressed air 
and utilize same. The object of reheating is to expand the compressed air, or, 
in other words, to increase its volume while its pressure is kept constant. Prof. 
Reidler, who is considered as one of the best authorities on compressed air, 
mentioned in his lectures that M. Victor Popp was the first to successfully use 
the reheating system with good results. Reheating of compressed air, however, 
had been done for a long time in mining work, but had never given good results, 
and was used principally in order to avoid the freezing of exhaust pipes of the 
motors or other machinery operated by compressed air. 

The reheaters used in the Popp Paris installation are of the cylindrical 
jacketted type, the air circulating through the jackets, while the heat derived from 
the fire inside of the cylinder is absorbed by the air after being deviated by means 
of a series of baffle plates. The results obtained have given very good satisfac- 
tion. 

It has been seen above in relation to hot air motors that the amount of heat 
stored in the compressed air is almost entirely transformed into mechanical work. 
Even with cast iron hot air n'otors, it has been proved that 80 per cent, of the 
heat was practically used. The table below shows the efficiency of several kinds 
of reheaters. 

TABLE 20. — TABLE OF AIR REHEATERS. 



Nature op Reheater. 



U O) HI 



■«s3 ^ - 
(u'O.5 ^ 



Temperature of the 
Air in the Heater C° 



When 
Entering 



When 
Leaving 



Number of Caloriee trans- 
mitted per hour 



Total 
Calories 



Per sq. 
meter of 
Surface 
Calories 



Per kilo, 
of Coke 
Calories 



Cast Iron Tubular Heater. 


1.3 


576 


70 


107" 


17900 


13760 


4470 


Wrought Iron Heater 


1.3 


313 


70 


184« 


17200 


13230 


4530 


Stove 


4.3 


1088 


50" 


175« 


39200 


9200 


5600 










The experiments from which this table was compiled were made by Prof. 
Gutermuth and show that one kilogramme of combustible will, under good cir- 
cumstances, give up as much as 5,600 calories in an air reheater. This result 



530 



^ PRODtrCTlON. 



being superior by at least 500 per cent, to the result obtained by the best triple 
expansion compound condensing engine, the question of reheating the air using 
same, is entitled to serious consideration. 

The amount of coal required for reheating air (for large motors) being 
about 0.09 of one kilogramme (i. e., 0.2 of the pound per H. P. per hour) 0.2 of 




FIG. 69. — AIR REHK.\TER. 

one pound is so small that it hardly needs to be taken into consideration, and 
thus in transmitting heat directly to the compressed air, the decrease of net 
efficiency of the fuel burned for reheating same is more than six times as efficient 
as that used to produce the compressed air. Thus o.i of one kilogramme (i. e., 
0.22 of one pound), will produce the same mechanical work in reheating as 0.6 
of one kilogramme or 1.3 pounds of coal through the medium of boilers and 
economical engines. 

If the reader wanted to thoroughly investigate the above assertions and 
results of experiments, it will be seen that for a very small increase of com- 




FIG. 70. — AIR REHEATER. 



bustible it will be possible to transmit large quantities of compressed air a great 
distance and make up not only the loss incurred through friction, etc., but obtain 
at the end of the pipe line a larger power than that originally pumped into same. 
For ordinary length of pipe lines and with reheating to 250 degrees C. above the 
atmospheric temperature, the power obtained at the end of the line was 30 per 
cent, above the power originally required to compress the air. 



PRODUCTION. 



231 



In gas motors as they exist to-day, the heat developed by the explosion may 
be transmitted directly or partially to the compressed air. The heat lost in the 
jacket of the cylinder may be absorbed by the compressed air and utilized in this 
way. When arrangements suitable to this end shall have been discovered, the 
affirmation, based upon scientific experiments, may be made that one horse-power 
can be produced with an expenditure of from 0.65 to 0.89 pounds of fuel, that is to 
say, with one-half of what the best steam engines consume. 

The little rotary Popp motors used in Paris have been made the subject of 
new study on the part of M. Gutermuth. The table below contains an abstract of 




FIG. 71. — COMPRESSED AIR ROTARY MOTOR. 

these experiments. The rotary motors, with automatic regulators to indicate the 
expansion necessary, without reheating the air, a volume of 1044.6 cubic feet per 
indicated horse-power per hour; and with reheating the air to about 122 degrees 
F. (50 degrees C), an expenditure of 835.7 cubic feet 24 m. of air per horse-power 
per hour. 

These little motors, from those of the power of a sewing machine, one- 
eighth horse-power, up to those one horse-power, are very well suited to light 
manufacturing and to the production of refrigeration in residences. 

The total efficiency of these little motors, in which the air is first heated to 
122 degrees F. (50 degrees C), is 43 per cent. 

The following is an abstract made from experiments upon piston motors : 

TABLE 21. 



MOTOR 


III 
HI 


1 


Temperature of the 
Air at Motor 


Air Consumption 

per H. P. per hour, 

cu. meters 




Admis- 
sion 


Exhaust 


Without 
Heating 


Heated 


Piston Machines 

Journaux, 2 H. P 


148 
283 
149 


"2.1 


"io" 

150" 
150" 
165« 


"O" 
34" 
18" 


34! i 





2 " 


19.7 


Boulet, 1 H. P 


24.3 


1 " 


23.13 







232 



PRODUCTION. 




It must be noted that the results in this table were obtained with old motors 
of one or two horse-power, bought in the market, and of very ordinary con- 
struction. The back-stroke presented considerable resistance. 

Thus in the Journaux machines of two horse-power, the actual efficiency 
was only from 65 to 75 per cent. The loss of energy due to friction was thus 
unusually great. The motors of good construction showed a mechanical efficiency 
of 91 per cent. 

If we suppose for the machines of which the table above treats, an efficiency 
of 85 per cent, and a better construction, the amount of air consumed per horse- 
power with a load would be 602.4, 741.7, and 710.4 cubic feet. The foregoing is 
an experiment with an old steam engine of 80 horse-power. This was a single 
cylinder machine, which had been used during six consecutive years as a steam 
engine, and which had been made to serve without any change as a compressed 
air motor with an air reheater in which the temperature of the air did not exceed 
338 degrees F. (170 degrees C). The minimum amount of air supplied to the 
machine was 452.7 cubic feet per horse-power per hour with air at 320 degrees F. 
This corresponds to a total efficiency of 80 per cent. The consumption of coke 
was 0.176 lbs. (.08 kil.), per horse-power per hour. 

The following table contains an abstract of different experiments relating to 
this machine : 

TABLE 22. — CONSUMPTION OF AIR BY AN ENGINE OF 8o H. P. 



MOTOR 



> 


>, 


M.S 


s 


'S^ 


OJ 






1- 





Temperature of Air 



Admission 



Discharge 



Consumption of Air per 
Hour in Cubic Feet 



Per H.-P. 



PerH.-P. 

with Free 

Brake 





54.3 


72.3 


1.29^C 
264.2'^F 


21.0c 
69.8^F 


462.77 


512.13 


Farcot's Machine of 80 H.-P., 


54.3 


72.3 


152. ^C 
305. 6F 


29^C 

84. 2F 


431.09 


468.35 


with a Single Cylinder. 


54.0 


72.3 


160°C 
320° 


35«>C 
95'^F 


418.55 


458.24 




40.0 


65.0 


170«C 
338° 


49°C 
120. 2°F 


432.12 


470.09 



Considering the results of experiments made with old reciprocating steam 
engines, those obtained with old style motors, the conclusion can be drawn that 
modern air motors show an efficiency which has never been attained by any other 
motor, or with an> other system of transformation of power. 

The smallest motors, below one horse-power, with a slight reheating of the 
air (to about 122 degrees F., 50 degrees C), give a total efficiency of almost 50 
per cent.; and the more powerful motors, such as the steam engine previously 
cited, with a moderate reheating, has a total efficiency of at least 80 per cent. 

In all this, exception is made of all improvements which may be brought 
about in the reheater and in the motors. 



PRODUCTION. 233 

The information relating to old machines is purposely given, since it shows 
that the total efficiency and the supply of air are at the extreme lowest limits ; the 
efficiency could not be less, but it might be sensibly increased with better motors. 

The total efficiencies include all the losses, and the actual quantity of air 
necessary to the production of one useful horse-power, and are based on the actual 
work which is required for the compression of the air at the central station. The 
loss of pressure in the conduit has been estimated at one atmosphere, although it 
might average less in the entire Paris plant. 

The figures given may, therefore, be considered as the minimum of efficiency 
in the working of compressed air, and we may adopt these figures, which are 
results obtained from old machines adapted to the use of compressed air, as a cer- 
tain basis. 

The scientific principles of the work and of the action of heat in air motors 
can not be contested and are generally known ; they have often been examined in 
these later days. In spite of that, I will give one glance at these scientific prin- 
ciples because all the experiments made with air motors establish a very close 
agreement between the volume of air given by the theoretical calculations and that 
really furnished to the machine in actual practice. 

Disagreeing results have been found only in certain cases when, by reason 
of the wire drawing of the air before entering the motor, the exact tension could 
not be given to a certainty, or when the measurement of the exact temperature at 
the beginning of a stroke of the piston was doubtful. But, whenever, these data 
can be furnished exactly, the volume of air given by calculation, and that actually 
supplied, agree. 

The effect of preliminary heating is to expand the air if the pressure re- 
mains constant ; for example, the unit volume of air that is raised from the tem- 
perature of 59 degrees F. to 302 degrees, 392 degrees and 572 degrees, becomes : 
V 59 : V 302 : V 392 : V 572 = 
i.o : 1.46 : 1.64 : 2. 

Therefore, by heating the air to 572 degrees (300 degrees C), its volume is 
double what it w.is at 59 degrees (15 degrees C), the pressure remaining con- 
stant, and the work which this air can do is increased in the proportions : 
A 59 : A 302 : A 392 : A 572 = 
1.0 : 1.45 : 1.53 : 1.90. 

The work can therefore be almost doubled by the heating of the air to 572 
degrees (300 degrees C). The heating of the air at a constant volume and with 
an increasing pressure is still more favorable. The work which it can do, by heat- 
ing it to 302 degrees (150 degrees C), is increased in the proportion of i to 1.7. 

This fact is made more striking'by a graphical representation. 

The work absorbed in the compressor in order to compress the air is com- 
pared with that furnished by this same air in the motor, after reheating. In all 
these diagrams there has been used as a base the work of compression, using this 
law of expansion : 

p v^-' = constant. 

In reality, the resistance in the compressor is sensibly less than this figure, 
even in the machines of the Paris plant. The theory is, therefore, unfavorable in 
comparison to the practice. 



234 



PRODUCTION. 



The compressed air loses heat in the pipes, and the volume of air decreases 
from ac to al ; besides, there has been admitted a loss of pressure in the city sys- 
tem indicated by the decrease from a to a^ in the diagrams, the corresponding loss 
of work is represented by the surface a, 1. a, 1^ a covered with cross hatching. 
The compressed air, because of the decrease of the pressure, occupies a more 
extended space, and extends to a. 1. We admit that this expansion is made accord- 
ing to an isothermic law. 

Before its entrance into the motor, the pressure and the volume of the air 
are indicated by a, Ij ; then, the air is heated, and, the pressure remaining constant, 
the volume is increased to m. The expansion of air in the motor and the produc- 
tion of work are made according to the law : 

14 + 
(p v) = const. 

This adiabatic expansion is supposed to be less favorable than that which is 
really produced. The curve of expansion rises higher than the adiabatic curve, 
because of the heat communicated from the walls of the cylinder. 

This graphical representation shows on one side the loss of work caused by 
the absorption of heat during compression, and by the friction in the conduit. 
This loss is compensated for by the reheating. There results from this: 



N \\ ^- i= 200" 




au^ 



FIG. 72. — DIAGRAM. 



for a loss of pressure of o.o6 atmospheres in the city conduit. 

We shall have, then, if the distribution is made over a radius of 7.46 miles 
(12 k.), and with a reheating of the air to 392 degrees F. (200 degrees C), a loss 
of work of 2.8 per cent. 

That is to say, of the work expended in the central station, 2.8 per cent, is 
lost by transmission, and is not compensated for by the reheating; but it must be 
noted that the total loss in friction in the compressor and the efficiency of the 
motor are supposed to be less favorable than they really are. 

When the loss of pressure in the conduit is 1.3 atmospheres (in transmitting 
to a distance of 16.16 miles), and when the temperature to which the air is heated 
is 392 degrees F.(200 degrees C), the losses are compensated for by this reheating 
of the air, to the amount of 8.7 per cent. 



t^flODltCTiON. 



2-35 



For a loss of pressure of 2 atmospheres (distance of 24.86 miles), the loss 
of work is 13.2 per cent. ; and finally, 




FIG. 'JZ- — DIAGRAM. 

For a loss of pressure of 3 atmospheres (in transmitting to a distance of 
37.28 miles), the loss of work" is 23.8 per cent. 



'1 . 


1 1. ^ 










1^ ^"ao 






V 


f 






a«-. 


^vv 


^">>». — 


"^"^-^t " ~ — 


_, Ht,Q 



FIG. 74. 



-DIAGRAM. 



In the diagram (Fig. 3), we have comparatively represented: 
The work absorbed in the compressor (curve c c). 
The loss of work due to cooling (c 1), 

And that due to the loss of pressure in the conduit c (a-ai; l-h) ; the pres- 
sure being decreased by one atmosphere. (System of 12.43 miles long.) 

WHEN THE COMPRESSED AIR ENTERS THE MOTOR. 

1. Without having been reheated, the expansion follows h, mz, an'S the 
work that may be utilized is represented by the surface ai, h, mz, of the diagram 

Fig- 3. 

The loss of work is then 43 per cent, of the work of compression. 

2. After having been heated^ to 392 degrees F. (200 degrees C). In this 
case, it will occupy the larger space h, m, the expansion is made accordingly to 
the adiabatic curve m, mi, and the loss of work not compensated for is 8.2 per cent. 

3. After having been heated to 392 degrees F., and after the injection of 
water, in such a way that the expansion of the air mingled with vapor follows 
m, ma, the work done exceeds the work of compression by 18 per cent. 



2.s6 



PRODUCTION. 



The diagram (Fig. 75) indicates a different result; the work expended in the 
compressor during a compression approximately isothermic, the increase of tem- 
perature being 72 degrees, which is the case for the more perfect compressors; 
this work is compared to the useful work produced in the motor, supposing that 



T(aue. 




FIG. 75. — DIAGRAM. 

the air has been heated to 482 degrees F., and that the expansion operates accord- 
mg to the law : p v 1.3 = const. 

Fig. 75 indicates this relation, the pressure of the air being 4 atmospheres. 

The relation between the work of compression as shown by the curve (Ac) 
and the work furnished by the motor (Al) is the following: 

For 8 atmos. of pressure : Ac : Al = i : 1.34 = 34 per cent. inc. 

For 6 atmos. of pressure : Ac : Al = i : 1.39 = 39 per cent. inc. 

For 4 atmos. of pressure : Ac : Al = i : 1.44 = 44 per cent. inc. 

The limits that may be practically reached by reheating the air and particu- 
larly by the double heating, are given in the following table : 

TABLE 23. 

SUPPLY OF AIR WITH DOUBLE EXPANSION .AND DOUBLE REHEATING. 



With reheating 

pv=const., k=1.41 

With reheating and injection of hot water 
k=1.2 




Air con- 
sumed per 
ind. H. P. 
per hour. 



330.8 

271.6 
254.2 
208.9 



Efficiency 

Ne. 



Nc 



=0.85 
=0.90 



If we except the function of the injection of water, there could be reached a 
supply of air per horse-power per hour of from 280 to 314 cubic feet, supposing an 
efficiency of 85 per cent. With this supply of air from 280 to 314 cubic feet, let us 
compare the work necessary to take in, per hour, 365.6 cubic feet of air, and to 
compress it to six atmospheres, work corresponding to one horse-power per hour. 
The excess of work is then 25 per cent, and the practical efficiency reaches 125 
per cent. 

APPLICATIONS OF COMPRESSED AIR IN PARIS. 
After having arrived, through the system of distribution, to the different 
points where it may be utilized, and after having passed through the air meters 



p^- 



.Tr- '- -'.-'■ 



PRODUCTION. 



237 




FIG. 76. — HUGHES AUTOMATIC POWER ACCUMULATOR — POPP SYSTEM. 




}-IG. 77.— PRESSURE REGULATOR— POPP SySTEH- 



238 PRODUCTION. 

to the subscribers, compressed air is applied to a host of employments, of which 
we will confine ourselves to enumerating the principal ones. 

Silk finishing machines. 

Embroidering machines. 

Scrap shears and tinsmith's shears. 

Turbines and ventilators. 

Lace machines. 

Machines for carding, calendering and scouring wool. 

Comb manufactories. 

Motors for dynamos ; electricity. 

Machines for physicians, pharmacists and dentists. 

Machines for seltzer water. 

Machines for making, kneading and chipping dough. 

Woodworking machines and tools. 

Sifting and polishing machines. 

Machines for boarding books and sealing envelopes. 

Shoemaking machines. 

Motors for hot air furnaces. 

Motors for ventilators. 

Motors for dynamos and cold storage rooms. 

Pumping of beer and wine. 

Elevators and hoists. 

Blow pipes. 

Works of the Exposition of 1900, construction of the piers of the bridge of 
Alexander, beneath the Seine, etc., etc. 

COST OF PRODUCTION OF COMPRESSED AIR IN PARIS. 

M. Bourdon, professor of the course in steam engines at I'ecole centrale des 
Arts et Manufacturers, and M. Meker, inspector in chief of machines for the city 
of Paris, were assigned to make the tests for admission of the machines. 

This test, the result of which we give hereinafter; was made Jan. 19, 1893, 
upon the machine No. 4; it must be noted that this machine had already been in 
service since December, 1891, and had thus been used for about thirteen months 
before the test. 

Average No. of revolutions per minute 59.635 

Average pressure of tlie steam in tlie boilers 157.16 lbs. 

Average pressure of the steam in the regulating valve of the 

small cylinder 146.16 lbs. 

Average vacuum in the condenser, in inches of mercury 28.20 lbs. 

Pressure of air in the compressors — 

Low pressure 32.71 lbs. 

High pressure 102.40 lbs. 

Temperature of the air on entering the compressors — low pressure. 40.7" F. 
Temperature of the air on leaving the compressor — high pressure. 69.1° 

Average temperature of the feed water after leaving the economizer 140.** 

Average temperature of the feed water before entering the econo* 

mizer '. 62.6" 

M. e. p., per sq. in., upon the steam pistons according indicator 
cards — 
High pressure cylinder head 43.02 Ifes, 



PRODUCTION. 



239 



High pressure cylinder cranlr 43.45 lbs. 

Intermediate cylinder head 17.11 lbs. 

Intermediate cylinder crank 17.19 lbs. 

Low pressure cylinder, head 8.99 lbs. 

Low pressure cylinder, crank 8.135 lbs. 

Indicated work, in horse powers, upon the steam pistons — 

High pressure cylinder, head 304,5 

High pressure cylinder, crank 305.5 

Intermediate cylinder, head 335.3 

Intermediate cylinder, crank 335.4 

Low pressure, head 61.5 

Low pressure, crank 326.4 

Total indicated work, in horse powers 1978.5 

Coal burned during the experiment of 8 hours. 11.49 tons 

Slag and cinders, 5.32 % 61 tons 

Coal (net) consumed during experiment 10.88 tons 

Coal (net) consumed per hour 1.36 tons 

Steam lost per hour in the pipe and by condensation 1255.9 lbs. 

Corresponding amount of coal lost per hour 139.5 lbs. 

Coal (net) consumed per hour for the running of the machine. . . . 2580.5 lbs. 
Coal (net) consumed per indicated horse power per hour by the 
cylinders— 

2 58 0.5 1.30 lbs. 

The work of compression developed by the machinery of I'Usine du qtiai 
de la Gare is deduced from the two following experiments, made towards the end 
of the year 1892, with three months between them : 



First experiment made by the engineers 
of PoppCo 



Second experiment made by Professor 
Gutermuth 



Number 
of revolu- 
tions per 
minute. 



Total 
mechanical 
efficiency. 



m 



Final pres- 
sure of air 
Pounds per 

sq. ft. 
(effective). 



1.08 
1.23 



Vol. of air 
taken into 

steam 
cylinders 
per H. P. 
per hour. 



10.21 
10.22 



Relation of 
real work 
of compres- 
sion to 
theoretical 
work. 



1.281 
1.192 



The average of these last two ratios is 1.237. 

The real efficiency of the work of compression of the air compressors in 

I 
question, which are, as has ben stated, of 200 horse-power each, is = 80.84 % 

1.237 
Numerous other studies have been made of the same compressors when 
they were in full operation. We relate hereafter the results of some of them, 
giving an illustration of each of the four following cases : 

1. A day of average production. 

2. A day of least production (Sunday), 

3. A month. 

4. A quarter, 



240 PRODUCTION. 

STATION QUAI DE A GAIiE. 

Production and expenses for one day — 

Number of revolutions of the machines 125,922 

Cubic feet of air taken in 22,456,501 

Horse power developed — - 

This includes all that relates to the lighting by electricity of 
the factory, to the water pumps and to divers pieces of 

accessory apparatus of the establishment 58,452 

Coal burned for the air compressors and their accessories 1,326,782 lbs. 

Per cubic feet of free air 2,1 lbs. 

Per indicated horse power 2.25 lbs. 

Total expenses of the day $556.74 

Cost of 3531.55 cubic feet of free air and compressed to 17.64 

lbs. (effective) .09 

Total production for a quarter — 

Summary of the number of cubic feet of free air compressed by 
the compressors at the Saint-Fargeau and Quai de la Gare 
stations — • 

Cuhic feet. 

Month of January — Saint-Fargeau and Quai de la Gare 66^.792,755 

Month of February — Quai de la Gare 548,483,406 

. Month of March — Quai de la Gare 532,506,886 

Total cubic feet of free air for the first quarter, 1892 1,749,783,047 

WORKS OF THE QUAI DE L.\ GARE — APRIL^ — SUMMARY OF QUANTITIES. 
Number of cubic feet of free air compressed (at 77° F. — during 

the month 652,651,629 

Average per day 21,755,054 

Number of horse power developed— during the month 1,696,135 

Average per day 56,537 

Average per hour 2,356 

Gross weight of coal burned for the compression of 

air 3,644,506 lbs. 

For electric lighting 42,227 lbs. 

t*er cubic feet of free air 0056 lbs. 

Per 1 horse power 2.1493 lbs. 

Per 1,000 revolutions 991.6000 lbs. 

Waste of coal — for the compression of air 557,762 lbs. 

Amount per 100 lbs. of coal '. . . . 15,33 lbs. 

Weight of pure carbon burned — for the compression 

of air 3,085,743 lbs. 

Per cubic feet of free air '0047 lbs. 

Per 1 horse power 1,8193 lbs. 

Per 1,000 revolutions 839,6 lbs. 

Difference between pure carbon and gross weight of coal burned 

— per cubic feet of free air .0009 lbs. 

Per 1 horse power 3300 lbs. 

Per 1,000 revolutions 152.016 lbs. 

Consumption per 100 cubic feet of free air of — Valve oil 0004 lbs. 

Lubricant 0013 lbs. 

Tallow grease 0001 lbs. 

Grease 0001 lbs. 

Cotton waste 0008 lbs. 

Cost of coal — per cuUic foot of free air — 

Coal— 3,686,733 lbs. at $5.40 per ton (2,000 lbs.) $9,963,36 

11,023 lbs, at $7,31 per ton (2,000 lbs,) 40.28 



$10,003.64 
which is $0.000015 per cubic foot of fr«e air. 



ir' 



PRODUCTION. 



241 



Summary of costs — 

Coal — 3,686,733 lbs. at $5.40 per ton (2,000 lbs.) $9,963.36 

11,023 lbs. at $7.31 per ton (2,000 lbs.) 40.28 

Water 96.50 

Lubricants and cotton waste for wiping 819.31 

City taxes -. 579.00 

Sundry expenses 1,065.55 

Total amount of pay rolls (officers and labor) 3,228.37 



$15,792.37 



Total cost per cubic foot of free air, $0.000024. 



TABLE 24. — SHOWING EVAPORATION FROM THE BOILERS. 



§ 

ll 

1! 

1 


Gross 
weight 
of coal 
burned 


li 
!l 

C0-C3 

■ 


Carbon 
burned 


h 
|i 

si 
is 

> 

< 


Average 
temperature 
of water in 
economizers 


No. of gallons 

of water 

evaporated 


Fuel 

burnt 

per 

hour 


Carbon 

burnt 

per 

hour 


No of gals. 

of water 
evaporated 

per hour 


§ 

OS 

S)B 

<1 


4) 

5a. 


J3 
1 


3 

K 

Si 
£ 

1 


5 

a 

.2 
1 


1 

< 


1 

< 


1 
^ 




a 

s 
ft 


be 

1 


1 



§ 
P. 

1 




11 


^1 


^1 




^1 




II 


2£ 

.0 = 

si 




1 


•1 


1 

CO 

to 

T-l 


1 


i 
S 

S5 


1 


© 




16 
•t— 1 


bo 
CO 


t 


be 
1 


t 

1 

1-5 


i 


1 



tH 
CD 

T— 1 


1 

00 

id 


1 

i 

CO 
1—1 


t 

CO 

c» 

CO 


g 

i 

■1— 1 


? 
^ 


00 



Remarks : — The apparent difference between the weight of coal burned as shown 
in this table and the total weight of coal consumed at the works, is accounted for by the 
fact that the coal burned in the first boiler is not included in the table ; this boiler is 
not yet provided with a water meter. 

Itemized list of the costs per cubic foot of free air — 

Coal $0.000015 

Water, taxes, oil, and sundry expenses 0.000004 

Pay rolls 0.000005 

$0.000024 

Total cost of free air— per cubic foot $0.000024 

Per horse power 0.129311 

Per day of 24 hours • 526.41 

Total production for a quarter — 

Summary of the number of cubic feet of free air used by the com- 
pressors of the factories "Saint Fargeau" and "Quai de la 
Gare" — 

January— Saint Fargeau and Qual de la Gare 668,792,755 

February— Qual de la Gare 583,798,906 

March - Quai de la Garo 532,506,880 

Total number of cubic feet of fvee air 1,783,098,547 



242 PRODUCTION. 

Engine, Steam — 

Diameter of high, pressure cylinder 2 ft. 9.47 in. 

Diameter of intermediate cylinder 4 ft. 7.12 in. 

Diameter of low pressure cylinder 6 ft. 6.74 in. 

Stroke (length) 4 ft. 7.12 in. 

Number of revolutions per minute 60 

Initial pressure of steam in the high pressure cylinder 142.22 lbs. 

Air cylinders — 

Diameter of low pressure cylinder 2 ft. 9.47 in. 

Diameter of high pressure cylinder 3 ft. 7.31 in. 

Pressure of the air 113.78 lbs. 



COMPRESSED AIR PLANT AT AINSWORTH. 

The first drill e.ver run by compressed air derived direct from falling water, 
under the Taylor patents, was started in operation in April at the camp of Ains- 
worth, the plant having been installed by the Kootenai Air Supply Company, of 
Nelson, B. C. 

The plant is now completed, and the compressed air automatically made, is 
being distributed throughout the ramifications of the camp and in the great va- 
riety of uses in mining camp work it is of more than passing interest to the great 
army of mine owners to whom compressed air is the necessity of their daily busi- 
ness, and no one can go to Ainsworth and see the novel features of the installa- 
tion there — the water collecting the free air from nature, carrying it into the 
bowels of the earth, and leaving it tightly boxed in a chamber compressed to 87 
lbs. pressure ready for the drill, and passing on down the creek to find its tor- 
tuous way to the ocean — without being impressed with the simplicity and effect- 
iveness of this great invention. 

The whole process of converting the raw energy into manufactured power 
ready for delivery through the pipe lines, is absolutely automatic, with no machin- 
ery of any kind, and so long as the water comes from the flume the compressed 
air is being made. 

DETAILS OF THE WATER POWER PLANT. 

The plant is located on Coffee Creek, to the south of Ainsworth, and about 
2J/2 miles from the principal operating mines. The creek has a flow varying from 
2,500 cubic feet per minute to several thousand, and the flume used is stave barrel 
construction, round steel bands being bolted around it every three feet. The 
flume is 1,350 feet in length, 5 feet diameter in the clear, the available head at the 
compressor being 107^ feet. The water at the compressor tower is received in 
a wooden tank 12 feet in diameter, height 20 feet ; a downflow pip passes from the 
water level through the bottom of this tank down perpendicularly and at the creek 
level a shaft was sunk 210 feet deep. The downflow pipe (which is 2 ft. 9. in. in 
diameter, outside measurement, of stave pipe construction throughout, the stay 
bands being set from 6 inches to 3 feet apart, dependent on the pressure to which 
the particular section is subjected) passes on down in the middle of this shaft, 



PRODUCTION. 



243 



•rminating in a great steel bell-shaped chamber at the bottom. The downflow 
»pe discharges into a deep groove, being open to the chamber in about its middle, 
le so-called groove being open to the chamber. The dimensions of this chamber 
re: height 17 feet, diameter 17 feet, the bell-shaped bottom standing about two 
;et from the bottom of the shaft, thus allowing the water to pass out. The dis- 
large of the mingled water and air from the downflow pipe into this groove 
luses it to swirl around the whole circumference of the chamber, some 51 feet, 




FIG. 78.— TOWER OF COMPRESSOR PLANT ON COFFEE CREEK, AINSWORTH DISTRICT. 



giving the air an opportunity to leave the water and to rise into that portion of 
the chamber which is above the line of the channel, while the water drops below 
to the rock bottom of the shaft, and thq water in the supply tank at the head rises 
in the shaft on the outside of the bell and the downflow pipe to the level of the 
creek. This back water column is an important factor in this system of com- 
pression ; its weight on the falling water in the downflow producing the pressure, 
every 27^^ inches of height of column of backwater increasing the pressure of air 
and water in the downflow pipe one pound: Thus, the shaft being 210 feet in 



244 



PRODUCTION. 



depth, and the depth of the groove, which is the effective back head, being 200 
feet, the air pressure roughly will be 200 feet divided by 27^ inches, or 87 pounds, 
which the gauge on the compressor records. The air in the chamber has been 
isothermally compressed, the moisture has been absorbed from it by the water 
which surrounds each globule in its passage down, and it goes to its useful work 
three times dryer than the original air that was entrained cold and pure. A goose- 
neck pipe reaches from the surface of the creek to the level of the dividing line 
between the air and water in the chamber, and whenever more air is being made 
than is being used, the air displaces the water, and the surplus passes out of this 




FIG. 79.— PIPE-LINE AIR COMPRESSOR PLANT AT AINSWORTH. 



pipe. It is discharging into nature through the pipe at the foot of the trestle in 
the accompanying photograph ; on the other hand, when more air is being drawn 
than is being made, a pressure valve on the surface of the ground shuts off the 
flow until the automatic air-maker catches up to the demand. In other words, by 
this device the pressure cannot vary to exceed one pound, or 2'7y2 inches of water 
column, and the compressor plant can be left alone to do its work perpetually. 

THE AIR-MAKER. 

The accompanying sketch plan shows the elevation and plan of the tank at 
the head of the trestle, where the water is received from the flume and the air i^ 
entrained. The air-maker is an inverted iron tanked funnel of the downflow pipe, 



PRODUCTION. 



245 



It is seven feet in diameter, and arranged with a screw lift, so that the amount of 
water allowed down the downflow pipe can be regulated. Around the circum- 
ference of this tank are inserted 3,000 pieces of ^-inch gas-pipe, the upper orifice 
of which is open to the air, the lower orifice being in the water, all of which must 
pass these lower orifices in rushing down the downflow pipe. The speed of the 
water in the downflow pipe is approximately 34^ feet per second, and the speed 
with which the air is drawn in with it will be nearly the same. The air is received 
by the water in millions of globules which retain their individuality, gradually 
becoming smaller in their passage down until finally liberated in the chamber 
below. 

THE EFFECTIVE WORK OF THE PLANT AT THE COMPRESSOR. 

The flume has a fall of 4 feet to the mile and the velocity of flow is figured 
at 3.72 feet per second, and the volume at 70 cubic feet per second. The actual 



The Taylor . . . 
Hydraulic .... 
Air Compressor 

Uetienat Ptn0eelin H*w 




FIG. 80. 



eft'ective head is 107^^ feet, and the available horse power allowing 75 per cent, 
efficiency is 620 H. P. The area of the downflow pipe being 4J/2 square feet and 
the area of the shaft 32 square feet. The speed of the water in the penstock or 
downflow pipe is 34]^ feet per second. The amount of free air taken in under 
these conditions is 85 cubic feet per second, or 12 cubic of air compressed to 87 
lbs. The motor air horse power will be 465. The efficiency of the plant will 
vary with flowage. At a later date cornplete data will be available under a variety 
of different conditions. 

THE PIPE LINE. 

In all the construction a light lap-welded pipe with screw joints has been 
used. The air leaves the compressor in a 9-inch pipe, branching some little dis- 
tance out, one branch being left for later construction^ the main branch running 



246 



PRODUCTION. 



north parallel to the Kootenai Lake to the mines round Loon Lake. This branch 
is of the following dimensions : 6,200 feet of 7^-inch pipe to the Dictator, 4,000 
feet of 6^-inch pipe along the west side of Loon Lake serving the Lady of the. 
Lake and Mamie mines, and 1,100 feet of 5-inch pipe branch northeast to the 
Tariff, Highlander, and the big tunnel of the Philadelphia Mining Company. 
The total length of straight line is 11,300 feet. The properties reached by the 
pipe line at present are : The Eden, Crescent, Last Chance, Dictator, King Solo- 
mon, Krao, Lady of the Lake, Mamie, Little Donald, Black Diamond, Little Phil, 
Tariff, Highlander, Albion, Spokane and Trinket, and the intermediate claims. 

The tunnel of the Philadelphia Mining Company is now in 700 feet, and is 
being driven from the bench above the Stevenson concentrator to tap the various 
ledges of the camp. This tunnel will give a depth of 900 feet at the highest point 




FIG. 81. 



of the hill ; it has already intercepted the Tariff vein, and drills supplied from the 
Taylor plant are driving the cross-cut tunnel ahead and drifting to the ore body 
on the Tariff ledge. 

ITS USEFUL WORK. 

Air was turned on to the pipe lines in the early part of April, and the first 
machine drill ever run by air direct from a column of water was started in the 
big tunnel of the Philadelphia Mining Company on the i6th of that month. Mr. 
E. E. Knowles, the mechanical engineer in charge of the plant, in writing of the 
plant, says : 

"The machine drill first started was a M-inch Rand, and is 12,000 feet from 
the compressor at Coffee Creek. It started without a hitch and with 85 pounds 
air pressure at the drill. This pressure is absolutely maintained at all times. I 
will venture the statement that there is not another machine in the world to-day 
working with as dry and pure air as this one, and I will also add that there is 
none giving better results. Manager Henry Stevenson, of the mining company 
above referred to, who is using the air, has expressed himself as being highly 



t»RODUCTION. 



247 



pleased with the air, and the pressure at this distance from the compressor was a 
surprise to him. Here is an instance of what the capabilities of this system of 
compressing air will do. The company referred to has a developed water power 
with a working head of 1,000 feet, and are using a Pelton wheel belted to a me- 
chanical compressor; yet this cheapest of plants to operate has been shut down 
for the simple reason that they are getting their power furnished them at their 
very door for just one-half what it was costing them for labor to run their plant, 
to say nothing of their investment, interest, oil and repairs. The compressor is 
running fine with not a soul nearer to it than three miles. At least it is presumed 
to be, as it is breathing into this machine drill at a rate that pleases the men who 
are running it and causes the muckers to get a hump on themselves. The work 




^>^^ 



at the Philadelphia tunnel is in charge of Mr. Sherwin, and in conversation with 
him he made the statement that the effective work of the air could not be heat; 
after shooting a round of eight holes the men go back to work in from 15 to 20 
minutes with the tunnel perfectly clear of impurities, and as clear as a bell in 
every way. Mr. Sherwin says that with all his experience with mechanical com- 
pressors, and some of them have had a capacity of 50 drills, he has never used air 
that is equal to the Ainsworth Air for clearing out smoke and impure air, and he 
also dwells on the fact that this air is an infinitely better power factor, inasmuch 
as it is always at constant pressure, and thereby the machine men are able to do 
better work and to break more ground. Mr. Stevenson, the general manager of 
the company, is equally well pleased with the air. 

THE COST OF THE PLANT. 

The installation at Ainsworth has cost in the neighborhood of $60,000, includ- 
ing incorporation, water power development and pipe line. Of this investment 



248 PRODUCTIO-^f. 

$20,cxx) will cover the pipe line cost, $10,000 the water-power improvements, and 
$30,000 the compressor cost. The latter cost was especially heavy in Ainsworth 
by reason of the fact that the shaft was sunk in an unusually hard formation and 
involved a cost of nearly $50 per foot. 

On the basis of a gross air power of 600 the output when 4,200 cubic feet per 
minute is used of the capacity of the water flume, this would represent a capital 
investment of $100 per horse power, or upon a motor horse power of 465 (allow- 
ing loss in delivery and loss in engines) the capital cost per horse power would 
be 130. 

The company is now selling the power delivered at the mines at $4 per drill, 
with a liberal reduction where more drills are used. The power is being used for 
pumping, hoisting, blacksmith forges and ventilation, the drill charge including 
ventilation. — The Mining Record. 



IS COMPRESSED AIR DESTINED TO BECOME THE RIVAL OF 
ELECTRICITY? 

Many and marvelous are the inventions which have grown out of electrical 
discoveries and research, until it seems, from their multiplicity and present 
state of perfection, that the spirit of invention which animated these creations 
must soon slumber. Mighty, indeed, has been the revolution in the affairs of 
man wrought by electricity; under the command of genius, even though its 
march has been in the wake of that other potent force in civilization — steam. 
Notwithstanding these achievements, the commercial and industrial world is 
fast becoming conscious of the fact that its future rapid strides and ultimate 
commercial supremacy, as a motive power, will depend on cheapening the pro- 
duction of this form of energy, so as to oust steam, which feeds wastefully on 
costly coal. If this problem remains much longer unsolved, its toiling in the 
field of transportation, and in the workshop, will be shared by some other of 
nature's forces, for investors have begun to seriously realize that the millions 
which have been expended for -franchises, dynamos, copper wire, etc., are not 
fruitful in dividends. It is stated that only one-fifth of the electric lighting 
stations in the United States are paying 4]^^%. Is it the uneconomical process 
of generating electricity by the initial power, steam, that is responsible for sev- 
enty-four electrical railroads, representing a billion and a half of dollars, being 
now in the hands of receivers? It is true that dynamos, in their present state of 
development, give out a high percentage of the engine's power imparted to them, 
and though we find the latter supplying in mechanical energy only 10% of that 
represented by the furnace heat, yet this wasteful process is not directly charge- 
able to the engine's incapacity to transform power delivered to it; but the 
trouble is due to the inability of the boiler to absorb and convert the major por- 
tion of the heat energy liberated in its fire-box. These significant facts have 
already influenced the recent course of electrical investments, and now the selec- 
tion of a cheap initial power for generating electricity is the all-important question 
of the day. Eminent engineers and scientists are at work upon this problem. 



r 



PRaDUCTION. 249 



some endeavoring to produce electricity direct from coal or chemicals by rapid 
decomposition, or other methods of electro-chemistry, with a view of locating 
power plants in the coal-fields, or by the sea, and telegraphing the currents so 
derived to the cities for consumption, while others are seeking sources of energy 
to be found in water-powers, or in the fitful but giant forces of nature, as tides 
and winds — and the promise recently given that Niagara would soon be a cap- 
tured Pegasus and harnessed, so as to become a useful wheel-horse, instead of a 
prancing, plunging steed, is now fulfilled. 

This development of power in the bosom of nature, many miles distant 
from industrial centers, presents other problems, requiring skill of the highest 
order, in their solution, namely: the economical transmission and distribution of 
currents of great magnitude and intense energy over long distances. When large 
accumulations of electric current are concentrated and prescribed to flow over a 
conducting wire, it becomes elusive and intractable as it flows forth, and rather 
than follow the pathway appointed for it to travel, it wastes itself, or passes to 
other substances and is dissipated so rapidly, that if it is transmitted any great 
distance the loss becomes so great as to render its transmission impracticable. 
Thus it can be seen that while electricity has not yet succeeded to its estate, the 
solution of these problems will mark a new era in the history of this subtle ele- 
ment. The applications of electric energy to industrial and commercial uses are 
so numerous and varied, and this singular phenomenon has received so much 
attention at the hands of the scientist, the engineer and the capitalist, that the 
world has become fascinated by its conquests, till now the impression prevails 
that electricity must necessarily become the motive power of the age. The writer 
does not claim that this, the above tendency, is a false one, but simply is set forth 
to show the reasons why other available forces in nature have received so little 
attention and consideration. Among these neglected forces, compressed air may 
be mentioned as a means of power transmission that has not received the attention 
it deserves. 

EARLY ATTEMPTS TO USE COMPRESSED AIR. 

The application of compressed air to industrial purposes dates from the 
close of the last century, although before this we find isolated attempts were made 
to apply it in a variety of ways. 

To the fertile brain of Dr. Papin, of France, we are indebted for the first 
suggestion of conveying parcels in a tube by compressed air, and he was the first 
to suggest the use of compressed air as a means of transmitting power. This dis- 
tinguished Frenchman went to the expense of putting his ideas into wood and 
metal, but the results of his experiments were not encouraging. This was about 
A. D. 1700. 

About a hundred years later, a Welsh engineer contrived an apparatus to 
utilize a water-power to work a blast furnace and machinery, a mile and a half 
distant, by compressed air, but the resulting blast was feeble. 

For a century or more water elevators operating by compressed air have 
been used in the mines at Chemnitz in Saxony. Vague descriptions of apparatus 
for using compressed air in the mechanical arts are found in early English patents 
and publications, but none, so far as known, were practically applied. In 1810, 
Medhurst, of England, patented means for conveying parcels by compressed air. 



250 PRODUCTION. 

There is no authentic record that his project was reduced to practice, and it stands 
simply as a mile-post on the road toward the advancement of knowledge in this 
direction. In 1824, Vallance revived the idea of Medhurst. Contributions to 
this science were also made by such pioneers as Pinkus, Cleeg, and Pilbrow. 

In 1837, the Italian government ordered experiments to establish the laws 
that govern air transmission, and improvements in methods and appliances have 
followed, resulting in the practical use of air for tunneling, in conveying parcels 
in tubes, and that valuable adjunct to railway trains — the air-brake. 

Along about 1857 an American, Dr, Gorrie, exhibited in London and else- 
where cold-producing machines, in which air was compressed in one cylinder, 
cooled whilst compressed, and re-expandcd in another cylinder, in a manner to 
utilize its expansive force. In 1859, a company was formed in London, and per- 
manent pipes laid down for conveying parcels by air; these lines of pipe were 
extended in 1865. During the same year Ericsson operated eighty sewing-ma- 
chines by compressed air in a factory in New York, 

Experimental sections of pneumatic dispatch tube for carrying passengers 
were built at Sydenham, England, and in New York in 1867. The line at Syden- 
ham was 600 yards long, and was traversed in fifty seconds with a pressure of 2^ 
ozs, per square inch. In 1872 Congress appropriated $15,000 for a pneumatic dis- 
patch tube between the Capitol and the Government Printing Office in Wash- 
ington, 

Other systems have been multiplied by telegraph and express companies 
in Vienna and Berlin, The Western Union Telegraph Company conveys mes- 
sages from lower Broadway to Twenty-third Street in New York, a distance of 
about three miles. They emplo}'- a vacuum, and the parcel travels between the 
terminals ordinarily in five minutes. Air was used for rock drilling in tunneling 
Mount Cenis, Hoosac, Arlburg, and other mountains. In 1879 air was used to 
propel cars on the Second Avenue Railroad, in New York. 

This was briefly the state of the art up to 1880, but the dreams of Papin 
and the hopes of Medhurst were but partially realized. The disappointments of 
the past are, however, no cause for apprehension of final successful application 
of air for transmitting power. Many of the grandest successes of the present 
were absolute failures in the early attempts. Previous to 1880 the waste of 
energy in the compression of air, and the sickly design and faulty construction 
of mechanism for using air, due largely to the ignorance of the principles of 
thermodynamics, retarded the introduction of air as a mode of transmitting 
power. At Mount Cenis tunnel, the loss in compression was fully 90%. In the 
modern compressors the loss is less than 16%. 

While compressed air has been used over and over again in a small way, 
and generally in a rough and uneconomical fashion, it was not until within a few 
years that any systematic attempt has been made to transmit and distribute this 
form of power for general consumption. To-day this is being successfully done 
in Paris and Birmingham, England, where the installations have given birth 
to applications and utilizations for purposes heretofore unthought of, with val- 
uable economic results, and a realization of high efficiency in its workings. 

In Paris the power is distributed not only to factories and electric lighting 
stations, but also finds domestic use, being sold to householders, restaurant 



s^^^r'" 



PRODUCTION. 251 

keepers, etc., keeping them supplied with an availaWe power which is turned to 
account in many useful ways, in producing the conveniences and comforts of 
life, while proving a welcome substitute for steam-power, with its heat, smoke, 
danger and waste. 

The commercial advantages derived from these air systems have resulted 
in their rapid extension, and in Paris elaborate provision is being made to in- 
crease the size of the plant with a view of supplying an aggregate of 25,000 H. P. 

THE POWER YIELDED. 

The general efficiency of this mode of transmitting power in these two sys- 
tems is conservatively put at from 80% to 85%, a showing that puts to flight the 
idea that the transmission of compressed air over a distance of several miles 
necessarily entails enormous losses. The attainment of this efficiency is gained 
by the help of another physical agent, in connection with the observance of cer- 
tain simple laws, and an explanation in regard thereto may be readily under- 
stood without wading too deep into the water of science ; and when understood 
will make clear the reasons why heretofore the progress in the introduction of a 
power so rich in possibilities has been impeded, while the truth becomes apparent 
that there is very little loss of power through its transmission if properly manip- 
ulated. In order that the reader may understand the elements involved in the 
solution of this problem it is necessary to gain a few preliminary ideas as to the 
behavior of air under prescribed conditions. Air under compression when im- 
pelled to move in a certain path is governed by laws quite different from those 
affecting electricity. As the air flows through the pipes the resistance of the 
surface of the same has to be overcome, and whenever compressed air meets re- 
sistance the pressure falls slightly, but this moderate reduction in pressure does 
not involve a loss of transmission, because what the air loses in pressure it gains 
in volume, so that its mechanical effect may at any point be easily restored to 
initial capacity by the application of a small amount of heat, and it has been found 
that by this simple expedient its capacity to do work at the points of consump- 
tion many miles from the power-station is enhanced with but a nominal cost, 
and that no more economical effect of the application of heat has ever been found 
than this method of annihilating the effects due to friction in the air's transmis- 
sion. An eminent English engineer declares that a quarter of a pound of coke 
per hour per indicated horse-power is sufficient to heat the air required in a 
moderate sized engine. Nor does this fairly illustrate its economic value, when 
we come to consider that it is capable of another important service (as alluded 
to in Dr. Gorrie's discovery) at the points of consumption, in the use of the by- 
product, the exhaust from the motors — for the purposes of ventilation and refrig- 
eration. In Paris the restaurants and*beer cellars are supplied with refrigerant 
in this manner, and which proves highly satisfactory in every respect and displaces 
the ice-melting method altogether, and in some cases is so sought after for cold 
storage that power is consumed essentially for its exhaust to use to this end. 

In this country compressed air is being pressed into service in small ways 
in every branch of industry, but the use to which the public is most familiar is 
probably in its application to railway trains in its adaptation to applying the 
brakes; but its utility and operation in this connection are scarcely appreciated 



252 PRODUCTION. 

until we come to consider the conditions of its use. While we have all noticed 
that trains cannot be gotten under way until the locomotive has run some dis- 
tance, to work up speed, it is doubtful if we have ever stopped to think of the 
tremendous momentum that is being piled up as that speed increases and the 
energy that must be destroyed in bringing a train to a sudden stop after it has 
gotten under way. It is estimated that the vast amount of energ>' that must be 
called into action at a moment's notice is greater than can be imparted to a pro- 
jectile by the largest of modern guns. Its triumph in this direction is daily evi- 
denced, and is the one important factor that has made speed in railway travel 
reconcilable with safety. How few of us have realized the importance of this 
daily performance. A train running 40 miles an hour traverses 59' in each 
second — lurking danger appears in sight — the loss of one second, through the lack 
of vigilance on the part of the engineer means its hastening on an errand of 
destruction by just 59'. By the touch of a lever the brakes are applied and the 
train that was rushing along at almost lightning speed is brought to a stand- 
still in a minimum of time and within a distance of 400' from where the danger 
was sighted, and this prodigious power that is brought to bear on the brakes is so 
ingeniously distributed and applied as to relieve the cars of all strain, while the 
train is promptly arrested in its flight without creating any commotion among 
the passengers or giving rise to a disagreeable shock. 

Joseph W. Buell, in Inventive Age. 



Editor Compressed Air: 

Dear Sir: — Knocking about the mines where compressed air is being 
used, I hear a good deal said about the deleterious effect of compressed air upon 
the health; only recently one foreman going so far as- to say that compressed air 
was very bad to breathe, as the result of compression gave a quality of air very 
different from that of the atmosphere. He went on to say that a chemical change 
took place in the air as the result of compression. 

Upon investigation, I found that they were using a very inferior quality 
of oil, and, running the compressor very hot, the result naturally followed that a 
certain amount of gas from the decomposition of the oil found its way into the 
headings, and naturally affected the men. 

It might be wise, therefore, that this matter should be discussed a bit in 
your admirable publication, and thoroughly explained to the unitiated. There 
seems to be a belief among miners that compressed air is a bad thing to breathe, 
or rather that the exhaust from drills in some way affects the health of the 
miner. 

Am I not right in my surmise that it is simply the use of a poor quality of 
oil in the compressor? Yours very truly, 

Benj. B. Lawrence, 
Mining Engineer. 

Denver, Col., March 13, 1897. 



PRODUCTION. 253 

In compressing air for the ordinary purposes of mining, temperatures be- 
tween 200 and 400 degrees are obtained in the air cylinder, notwithstanding the 
cooling jackets. This tends to volatilize the oil, carrying gases into the mine 
with the air. A high grade oil will be comparatively free from objection in this 
respect, but in no case is it likely that a chemical change takes place in the air, 
or that there is anything unhealthy about it. Many of the germs or organisms 
which exist in free air are destroyed by the heat of compression. A process has 
been recently introduced for the preservation of fruits and meats by confining 
them in dry air which had previously been compressed and dried, the purpose 
of compression being mainly to kill the germs. Compound compression or com- 
pression in stages aids in preventing the smell from oil. This is natural, be- 
cause in compound compression the heat does not reach as high a point as in 
single stage compression. 



The effect upon men working in a confined space where pure air is con- 
tinually being exhausted, should have a tendency to make a model workman out 
of the laziest man. 

There is no reason to believe that heat (even intense heat) should cause 
a chemical change in the two gases composing the mechanical mixture, air. The 
heat of compression in the average compressor does not rise much above 350 deg. 
F. ; and if any foreign substance is present, such as oil (in excess often), there 
will be a tendency for it to volatilize at that temperature unless the quality is such 
that the 350 deg. F. will have no volatilizing effect upon it. 

It is only necessary to refer to the use of compressed air in caissons to 
prove that the air undergoes no chemical change by virtue of the heat of com- 
pression. The only difficulty met with there is on account of the effect of the 
pressure on the human body; the extra amount of oxygen present in a caisson 
has the most exhilarating effect upon the workmen. 



Referring to the deleterious effect of compressed air on human life, I asked 
Professor Hart, the chemist, if air underwent any change in compressing and 
heating, and he said not, and that if there was any odor in compressed air it 
was caused by the oil. This was what I supposed to be the case. From my 
own experience, I must admit that there is an odor to compressed air which it 
undoubtedly receives partly by some of the oil becoming volatilized owing to 
using poor oil, and where excessive heat is in the air due to poor cooling, but 
mostly by the air passing through the receiver and pipe line which are more or 
less coated with oil — the air, even whefl cold, being able to take up odors. A 
good example of this would be the delightful odor one meets when passing 
through a pine forest. It does not follow that air in which an odor is perceptible 
is unhealthy, for in the case of a pine forest the odor is both agreeable and 
healthy, while with many antiseptics the odor is disagreeable, but still healthy. 
I do not think compressed air any exception to the rule, for the slight odor it has 
is not disagreeable, and as the air was pure when it entered the compressor and 
had nothing to mix with except the small amount of oil that was fed to the air 



254 PRODUCTION. 

cylinder for lubrication, this only amounting to about one pint of oil for every 
1,000,000 cu. ft. of free air, or such a small percentage that the air itself should 
not be appreciably changed. 

Wherever the odor of compressed air becomes objectionable, it must be 
due to the air being excessively hot and poor oil used, that the oil is turned into 
a gas which mixes with the air, and also that a great excess of oil is used; but 
even with the most unfavorable conditions, the percentage of oil would be so 
small that the large amount of air with which it was mixed should have no dele- 
terious effect on the life of people who were inhaling same. With good oil, of 
which only a small quantity is necessary, a good compressor with good cooling, 
no oil should ever be turned into a gas. 



TRANSMISSION. 255 



TRANSMISSION 



THE USES AND ADVANTAGES OF A PUBLIC SUPPLY OF COM- 
PRESSED AIR.* 



BY FRANK RICHARDS. 



It occurs to me that it will be of interest to many readers of the "American 
Machinist," and that I will be doing an actual, practical service to many of them, 
if I try to put in easily readable shape some statement of what could be done — 
say in any of the large cities — if a supply of compressed air should be established 
and maintained, and the air distributed to all customers who should want it, as 
water and gas are now so universally provided. 

There are no difficulties or uncertainties whatever in the way of establish- 
ing a general compressed air supply. Air compressors of considerable capacity 
are now made, and nearly as well understood as the steam engine, and their per- 
formance can be computed and guaranteed with great accuracy and reliability. 
The conveyance and distribution of the compressed air involve no difficult prob- 
lems, no experimenting, no risks, no enormous expenses. Comparatively small 
pipes will convey a great amount of power, and they can be cheaply laid, and made 
and kept tight, by the resources of everyday mechanical skill. No expansion 
strains of any importance occur, as with steam pipes. The air, as delivered to cus- 
tomers, can be metered as accurately as gas ; so that everything can be conducted 
upon a thorough business- basis. 

It may be better at the latter end, rather than at the beginning, to go into 
a detailed consideration of the cost of the compressing plant, and of its main- 
tenance and operation, with the details of its construction and arrangement. It 
will be better first to see whether the service would be worth anything to us — 
and if so, how much — before proceeding to consider the cost of it. 

It is necessary at the outset to determine what pressure of air shall be 
maintained in the system, as the scope and mode of its employment must, to a 
certain extent, be limited or controlled by that. We may assume, then, a pressure 
of 100 pounds, gauge, which, upon the whole, and at this stage of the game, may 
be better adapted to an all-around service than any other pressure, although much 
might be said in favor of a pressure much higher. 

Although, as I said above, we will not now consider in detail the cost of 

compressing and delivering the air, still, in order to have some practical idea of 

the cost — and, therefore, the saving or the loss in the use of the air, under the 

various conditions which we may mention — it will be desirable to have some ap- 

♦ '• American Machinist," 



256 TRANSMISSION. 

proximate figures for a standard by which we may measure the economy of the air 
service as compared with other means applicable to each individual case. 

It is generally found to be most convenient in making computations or 
comparisons, or in keeping records or accounts pertaining to compressed air 
practice, to conduct all such transactions upon a free-air basis. Free air is the 
volume that we have at the beginning and at the termination of compressed air 
operations ; but during the use of the air, the volume will be less and will vary at 
different stages. Supposing the air to be compressed at or near the sea level, 
and at normal barometric pressure, the volume actually delivered at lOO pounds 
gauge pressure, and at normal temperature, will be only .1304 of the volume of 
free air; or, 1,000 cubic feet of free air will, as actually delive-red to the customer, 
be only 130.4 cubic feet. 

Let us assume, then, for the sake of keeping the cost feature before us in 
our compressed air practice, that the air is delivered to the consumer at an estab- 
lished and uniform rate of five cents per thousand cubic feet of free air — the 
pressure maintained being, as before assumed, 100 pounds by the gauge. This 
estimate of cost is, for the present, to be taken entirely upon trust ; although I 
could easily show that the rate would be a perfectly safe and profitable one for a 
company who should undertake the compressing and furnishing of the air and 
develope sufficient business in it. With coal at $5 per ton (and not talking any 
nonsense about utilizing idle water powers, where the water is running to waste, 
and where consequently it would cost nothing), the total fuel cost for compressing 
the air under the above conditions would be decidedly less than two cents per 
thousand feet of free air. 

The establishment of a public supply of compressed air could not fail to 
open for it a wide field of usefulness. It is an undeniable fact that it can boast a 
range and variety of applicability, a Briarean dexterity, possessed by no other 
transmissible medium. To some extent, in the single function of power transmis- 
sion, it would find itself in competition — or, rather, in comparison — with the hy- 
draulic system, with steam, and with electricity. Water transmitted under pres- 
sure of 1,200 pounds or more, is in use in various cities of Great Britain, and 
though the range of its usefulness is restricted to power transmission alone, and 
that only under narrow conditions of application, it is still an established success, 
and moderately remunerative to its promotors. Steam, though excellent in the 
development of power when it gets at its work, and though also available as a 
conveyor of heat, is not a good traveler, and its inability in this particular is fatal 
to its extensive employment. Electricity, upon the other hand, is the most 
sprightly and ubiquitous of travelers, and a ready distributor of both light and 
power — the latter almost exclusively by means of whirling motors and trains of 
reducing mechanism, while air may communicate its power in various ways — by 
the motor or engine at high speeds, or by slow, dead pressure when so required; 
and in addition to its universal adaptability for power transmission, it has numer- 
ous other modes of making itself useful which are possessed by it alone ; and it 
has, above all, the unique advantage of costing nothing, except as it is used, and 
that it charges only for its actual services when employed. 



TRANSMISSION. 257 

^VANTAGES OF COMPRESSED AIR FOR TRANSMITTING POWER. 

In a communication to the Societe de I'lndustrie Minerale of France, M. 
>rtier made a critical examination of the advantages and disadvantages of 
impressed air as an agent for the transmission of power, showing clearly by 
lathematical calculation, that the advantages far outweigh the disadvantages. 
We have not sufficient space to reproduce this valuable treatise, but we select the 
more practical portions and also the conclusions arrived at by the eminent in- 
ventor of the diametral ventilator. 

While cornpound air compressors have already been adopted to a certain 
extent, the use of multiple expansion has hitherto been limited to a compounding 
of the motors, the reason of which limitation must be sought in the fact that 
compound engines cost more than those not compounded, while it is difficult, 
without warmed intermediate receivers, to restore its initial temperature to ex- 
panded air. Instead, however, of compounding each compressed air motor inde- 
pendently, it would be better to compound them mutually, the exhaust air from 
one series of motors being collected for supplying another series in a pipe under 
moderate pressure, laid side by side with the high pressure mains. 

There is, moreover, nothing to prevent various lengths of this supplemen- 
tary pipe from being connected, first with one another, and afterwards with the 
receiver of the successive compressors, in which case a series of compoundings 
would be obtained, notwithstanding differences in the volumes of air exhausted 
from the two series of motors, and in this manner something akin to the system 
of electric distribution with three conductors would be effected, without, how- 
ever, its complication. 

Besides great saving in the first cost of the motors, a mutual compounding 
would give them considerable elasticity of power without loss in yield, because 
with two pipes under different pressures, a moderate effective pressure, double 
or triple, according to the method of connecting the admission and exhaust, may 
be applied to the same cylinder. Advantage may thus be taken in the same 
cylinder with normal dimensions of the original economy afforded by low com- 
pression, because the possibility of admitting a threefold pressure would permit 
of overcoming a special resistance of making unusual efforts. In this manner 
successive stages of compounding introduced into the utilization apparatus would 
greatly increase the useful effect of moderating or governing, by permitting the 
dimensions of the motors to be reduced and the wire-drawing of the compressed 
air in the cylinder to be diminished. 

The co-efficient of general yield, taking into consideration the imperfect 
general yield, the losses of work corresponding with losses of pressure, and the 
advantages of multiple compressions at the beginning and end of the operation, 
is calculated mathematically by the author, who concludes that if only the adia- 
batic method — that at equal pressures — be adopted, which most nearly approaches 
the ordinary conditions of practice, the following useful effects will be obtained : 
With a single compression, 0.533; with a double compression, 0.C81 ; and with 
quadruple compression,' 0.753. 

These figures suppose the most unfavorable conditions that can occur, vie.: 
no cooling down in the compressing cylinders and no reheatThg in those wherein 
the air is again expanded; but at the same time they suppose the favorable con- 



258 TRANSMISSION. 

dition of the air returning to its initial temperatures after each stage in the mul- 
tiple compression. Although a quadruple compression may be obtained per- 
fectly well, a double expansion is all that can be hoped for in practice. Taking 
everything into account, it will be very near the truth to regard the original yield 
or useful effect as varying between 55 and 75 per cent. 

Simple air compressors of good construction show a ratio of 0.85 between 
the work indicated on the air pistons and that on the steam pistons, or 0.93 for 
the yield of the air system and 0.93 for that of the steam system, while for the 
receptor motors only a rough mean can be given, probably near upon 75 per cent. 
The maximum value of the general useful effect, supposing the pipes absolutely 
tight, will therefore be 0.75X0.93X0.75=0.523; but without multiple compressions 
this figure will be only 0.384, supposing the work, of expansion to be completely 
utilized, which is practically impossible with a single expansion without re- 
heating.* 

As is well known, the compression of air in a space which exerts no action 
upon it causes heating, while expansion in a similarly inert space causes cooling, 
and with production or utilization at constant pressure the variation of tem- 
perature may be obtained in centigrade degrees by dividing the work (expressed 
in kilogrammetres* per kilogramme of air) by 102.7 F. 

To give an example for an expansion at constant pressure corresponding 
with a ratio of 6.25, the theoretical lowering of temperature will be 120° cent., 
while for a ratio of 2.5 it will only be 60° cent. In the former case, working 
would be impossible owing to the oil becoming solidified, and the watery vapor 
in the air being frozen; but in the second case admissible conditions may be ob- 
tained, especially if the exhaust be allowed to commence at a pressure slightly 
greater than the back pressures. 

Thus, not only does the use of multiple expansions improve the useful 
effect, but even renders it possible, which would not otherwise be the case. If 
the initial temperature of utilization be not the same as that of production, the 
useful effect found for identity of initial temperature must be multiplied by the 
ratio of the temperatures. 

The yield may be increased (i) by lowering the initial temperature of 
production, although little more can be practically done in this connection than 
to draw the air for compression from a cool cellar and (2) by raising the tem- 
perature of the compressed air immediately before it is utilized. The available 
energy is then, as it were, expanded under the action of heat, just like air itself, 
and with the same co-efficient of expansion, the improvement thus obtainable 
having theoretically no limit, so that the yield of a power transmission by com- 
. pressed air may be considerably greater than unity ; and it is in this respect that 
compressed air differs widely from the other agents for transmitting power such 
as electricity and water under pressure, which admit of no such increase, and 
always yield less work than what has been entrusted to them. 

It is evident that this "expansion," or increase of energy, cannot be ob- 
tained without the consumption of fuel, but this supplementary work is obtained 
so cheaply and simply that no other is more economical, not even the natural 

*A kilogrammetre (7.233 footpounds) represents the effort required to raise a kilogramme 
(2.8 lbs.) the height of 1 metre (3 ft. 3% in.). 



TRANSMISSION. 259 

forces, which are regarded as gratuitous. In any case, whether the expansion 
leaves the air at a relatively high temperature or whether it determines an in- 
tensely refrigerating action, a difference will be set up that may be utilized me- 

lanically so that some of the heat imparted will be recovered, thus reducing ex- 

;nse. 

Indeed, there is a case in which the saving that may be obtained is abso- 
lutely integral, viz. : when the expansion supposed forms one of a multiple series 
In which the initial temperature becomes raised by the reheating every time to the 

ime figure, and in that case the residual temperature of the air at the end of 

ich partial expansion constitutes a net gain for the next reheating. 

For a multiple utilization, comprising a certain number of stages, each 

)rresponding with the same ratio of compression, with the same initial absolute 
iperature reheated, and consequently with the same sum of work produced, 

le mean thermic yield, which in this case is the arithmetical mean of the partial 
rields, may in any case rise above 50 per cent, even, under ordinary circumstances. 
Considering that the cylinders of gas engines readily accommodate them- 
selves to high temperatures, an exact doubling of the energy available at the end 
of the operation, i. e., an integral reconstitution of the energy furnished at the 
commencement may be obtained — and this with a very slight expenditure of 
heat units, inasmuch as the operation of reheating has a thermic yield ten times 
that of good engines. 

The multiple compression of air by the natural forces, its transmission at 
high pressure, and its expansion in a series of stages after considerable and re- 
peated heating, afford a very welcome solution of the problem of the economical 
production and transmission of power ; and this system, economizing the natural 
forces, the effect of which it multiplies, and the fuel which it consumes, offers 
nothing but what is very acceptable, provided the pipes be perfectly tight, which, 
however, is unfortunately not yet attained in practice. The following is a sum- 
mary of the conclusions arrived at by the author: 

Compressed air, regarded as an agent for transmitting power, is just what 
it is made, its value being exactly proportioned to that of the mechanical and 
calorific conditions which preside at its production and utilization. With high 
adiabatic compressions, rendering illusory all effective expansion, the yields ob- 
tained are miserably small ; and on the other hand, although with low pressures 
this original defect is absent, the dimensions of the pipes and apparatus then 
become so large as to be prohibitive. 

With a series of successive compressions, however, even at constant pres- 
sure, and especially with a mutual compounding between motors, sufficiently far 
apart for the air partially expanded in passing between them to acquire the sur- 
rounding temperature, a useful effect of 50 per cent, may easily be obtained, and 
that with pipes and cylinders of moderate dimensions. 

While the other agents of power transmission, such as electricity and 
water under pressure, correspond with a strictly defined amount of energy avail- 
able, compressed air, in addition to the amount of work which it is capable of 
giving out at a constant pressure and at the surrounding temperature, carries 
with it a credit, theoretically unlimited, for transforming into power the artificial 
heat which may be communicated to it; and this transformation is effected with 



26o TRANSMISSION. 

so high a thermal yield that the supplementary work thus obtained is almost 
gratuitous. 

In other words, the purchaser of a given weight of compressed air acquires 
at the same time the right of obtaining, without complication of any consequence, 
and with a very slight expenditure of fuel, an artificial quantum of energy at 
least equal to that of the natural energy imparted to it directly. 

This special faculty added to absolute elasticity of speed, both of the com- 
pressors and the motors, and also to the possibility of regulating or storing up 
compressed air, constitutes an individual feature of the highest importance, which 
may often justify a preference being given to this agent of power transmission. 

J. W. PEARSE, 



AIR VS. ELECTRICITY IN LONG DISTANCE TRANSMISSION.* 



By W. S. Norman. 



The high efficiency now obtainable by the Taylor system of hydraulically 
compressing air which develops 75 per cent, of the horse power of any given 
water power in compressed air, the excessive dryness and low temperature of the 
air so compressed, thus reducing to a minimum the loss in delivery, brings com- 
pressed air forward as the most economic form of delivering power in long dis- 
tance transmission ; and I propose to show in this article that for the uses of a 
mining camp, compressed air under the Taylor system is the cheapest in its first 
cost of installation, and immeasurably the cheapest in its cost of operation in com- 
parison with electric power. 

The Taylor system of hydraulically compressing air was fully explained in 
an article which appeared in the May number of the Mining Record, and the 
accompanying plan of the plant now in process of installation at Ainsworth, B. 
C, will refresh the memory of the reader as to the principle involved. The Ains- 
worth plant will develop 75 per cent, of the horse power of the stream in actual 
compressed air, at a pressure of 90 pounds, and the air so delivered will be three 
times drier than the external atmosphere, and of the same temperature as the 
v/ater which compresses it. 

In comparing any two systems of power transmission, relative compari- 
sons must be made upon the following points: 

1. Original cost of installation. 

2. Cost of maintenance and operation, including their relation to load 
factor. 

3. Efficiency of systems. 

4. Relative simplicity of systems, and the superior advantages of operat- 
ing with simple machinery. 

Starting with the acknowledged condition of all mining operations, namely, 
that a large portion of the ultimate power required must be compressed air, 
whether it is mechanically compressed by steam or from turbines, or from elec- 
tricity transmitted by electric wires and converted by electric motors and mechan- 



* British Columbia Mining Record. 



TRANSMISSION. 



261 




FIG. 83. — ^AIR COMPRESSOR PLANT INSTALLED AT AINSWORTH. 



262 



TRANSMtSSION. 



ical compressors, or by the Taylor system, the absolute demand of the camp for a 
large share of its power must be air to drive the percussion drill, to ventilate 
the underground workings and to actuate the pumps; and since the major por- 
tion of the work to be done in the mine has to be performed by air, the general 
custom is to run all motive power by air, thus bringing the generating station 
under one roof. 

For the purpose of comparison, we will assume the existence of a water 
power eight miles from a group of mines, v/here the head is high and the cost of 
development is relatively low, the conditions to be fulfilled being the delivery of 
10,000 cubic feet of free air at six atmospheres pressure, or sufficient free air to 
represent i,ooo net air h. p. delivered, and to actuate say 150 drills in ordinary 
rock. We shall consider the case of an electric plant at a water power actuating 
motors in the heart of a mining district, the motors driving mechanical com- 
pressors in a central station, the air being delivered by mains to the various mines, 




FIG. 84. 

though a very common practice throughout the United States and Canada is 
the use of small separate mechanical compressors at the various properties, each 
actuated by its own separate motor, and each employing its own separate force of 
operators, thus materially increasing the cost of the air h. p. delivered at the drill. 
The air h. p., however, which the conditions laid down above call for is not the 
air h. p. read from the indicator card of the compressor, which tells us nothing of 
the temperature of the air nor of the amount of moisture therein contained, but 
the air h. p. at its working conditions at the drill, where the moisture has been 
drawn off and where its temperature has been reduced almost to atmospheric con- 
ditions. To reach this degree of perfection, the mechanical compressors must 
deliver an air efficiency of 1,000 h. p., or 10,000 cubic feet of free air per minute 
at the mine, and our mechanical compressors, therefore, should have at least 1,500 
gross h. p. capacity, and be actuated by electric motors of at least 2,000 h. p. 
capacity, and our water power must possess 3,000 gross h. p., which will give 
2,400 net h. p. on the wheel shaft, and will give a dynamic force of 2,200 h. p., 
delivering 2,000 h. p. over the line at the electric motors. With the Taylor system 



TRANSMISSION. 263 

there is but the one transformation, that from the water to the compressed air, 
and no moving mechanism is used in the transformation. The water rapidly- 
flowing down the downflow pipe entrains the air, which is compressed in the 
receiving tank by the returning column of water, and from this tank it is auto- 
matically delivered absolutely free from moisture ready for use at the drill. The 
amount of loss in transmission is almost inappreciable if we care to invest a 
sufficient amount in pipe line. In the West, however, where freights are high 
and the pipe line cost is greater than the sinking of shaft cost, we will figure on a 
wider drop of pressure in the pipe line. At the compressor we will have a shaft 
sunk deep enough to produce 125 pounds pressure and allow 45 pounds loss of 
pressure in the line, delivering at the terminal at 80 pounds. This would be 
equivalent to a loss of 12 per cent. Reduction of pressure increases the volume 
of the air, and by using a 15-inch wrought iron pipe we can deliver at the terminal 
end' 10,500 cubic feet of free air per minute, isothermally, and not adiabatically 
compressed, as in the case of all mechanical compressors, the h. p. of which 
would be rather more than 20 per cent, greater than the same volume of air 
adiabatically compressed. With these losses we should, therefore, require 1,250 
h. p. at the compressor, and a gross h. p. in water of 1,700 h. p. By raising the 
initial pressure to 200 pounds, and making a drop o£ pressure of 100 pounds in 
the pipe line, which would represent a loss of about 19 per cent, due to friction, 
the 1,000 h. p. could be carried in a 12-inch main, thus saving one-tenth in weight 
of iron in the plant. 

I — ORIGINAL COST OF INSTALLATION. 

The cost of water-power development varies with the local conditions, and 
for the sake of camparison we will take a water power having a high head, 
where the power can be developed, exclusive of the waterwheel cost, at $20 per h. 
p. The following will be the cost of the electric plant, according to the figures 
given in Dr. Louis Bell's "Electrical Power Transmission," 1897: — 

Electric plant, 3,000 gross h. p., at $20 per h. p $ 60,000 

2,200 h. p. electric generators, at $12 per h. p 26,400 

2,200 h. p. in transformers, at $10 per h. p 22,000 

Pole lines and wires, eight miles 35,ooo 

2,750 h. p. in water-wheels, at $15 per h. p., set in place 41,250 

Station building and equipment 10,000 

2,000 h. p. step-down transformers 22,000 

2,000 h. p. in motors, at $12 per h. p 24,000 

1,500 h. p. compressor plant, set up in place 75,ooo 

Miscellaneous 20,000 

Total $335,650 

The following will be the cost of the air plant under the Taylor system : — 

1,750 gross h. p. water power to develop, at $20 .$35,000 

275-foot shaft, 8 X 8 10,000 



264 TRANSMISSION. 

Down-flow pipe and compressor tank S^ooo 

8 miles 15-in. pipe line, all set in place, at $1.50 per ft. 63,360 
Sundries 10,000 

Total $123,360 

2. — COST OF MAINTENANCE AND OPERATION. 

The following are the expenses of the electric plant : — 

Superintendent of whole plant $ 3,600 

4 men at power generating station, at $3 each per day. 4,380 
4 men at compressor station and sub-electric station, at 

$3 each per day 4,380 

Repairs to plant, 4 per cent, on capital cost 13,483 

Insurance, 2 per cent, on $150,000 3,000 

Taxes, 2 per cent 3,000 

2 linemen at $3 and team at $1 per day 2,555 

Interest on investment, at 6 per cent 20,235 

Sinking Fund, at 4 per cent 13,488 

Clerical work and office expenses 4,000 

Total $72,126 

Should the power transmission plant be at a distance greater than ten 
miles, then the investment cost would be greater, as a step-down transformer 
station would be rendered necessary, entailing additional capital and additional 
operating charges. This brings the annual charge per air h. p. delivered at the 
drill up to $72.12, and it is very questionable to-day whether in practice, under the 
most favorable conditions, a rate as low as this has ever been realized. It should 
be remembered that in almost every mining camp where electricity is used for 
the driving of compressors, numbers of small compressors are used on each 
different property, driven by their own separate motor, each entailing a separate 
operating force, and this, of course, adds largely to the cost of the air h. p. deliv- 
ered at the drill. If, for instance, the electric h. p. is rented from a central com- 
pany at a charge of say $50 per h. p. per annum, delivered at the motor in the 
camp, it can be seen from the above figures that the air h. p. delivered at the drill 
will cost between $150 and $200 per annum. 

The following are the rriaintenance and operating expenses of the Taylor 
air plant: — 

Maintenance of pipe line, at 4 per cent $ 2,534 

One man at station to keep racks clean 1,000 

Depreciation in plant taken at 2 per cent, on account of 

absence of machinery 2,267 

Management a/nd interest 10,801 

Total .;. $16,602 

Or a h. p. cost of $16.60 per annum delivered at the drill. 
An important point to consider is the relation of the load factor in a power- 
generating plant. The load factor in a plant reaches its maximum of 100 per cent. 



TRANSMISSION. 



265 



when it operates at its full maximum capacity during the whole twenty-four 
hours. If it operates at less than its maximum capacity, or less than the twenty- 
four hours, then the load factor cannot reach lOO per cent. The great object in 
all electric plants is to raise the load factor, because it is found in actual experi- 
ence that the operating expenses do not increase as the load-factor increases, nor 
do they diminish as the load factor diminishes. Very few electric plants attain a 
load factor exceeding 50 per cent. In the case of the electric plant given above 
by Dr. Bell, he considers that if it runs on a load factor of 38 it attains all that 
can be expected. The point is just this: As has been mentioned, the operating 
expenses in an electric plant do not fall as the load factor falls. If the load factor 
falls down, say as much as 60 below its maximum, the operating expenses will 




FIG. 85. 



only fall about 10 per cent. In the case of the Taylor air system, the operating 
expenses are merely nominal, being in the case considered only $1,000 for a man 
to keep the water racks clean, so that this factor of loss due to a low and variable 
load factor is almost entirely eliminated in the Taylor air plant. 

EFFICIENCY OF SYSTEMS. 

In the case of the electric proposition there is a series of eight losses from 
transformation before the drill is actuated in the face of the stopes of the mine : 
First, from the water to the water-wheel; second, from the water-wheel to the 
dynamo; third, from the dynamo to the transformer; fourth, from the transformer 
to the line; fifth, from the line to the step-down transformer; sixth, from the 
transformer to the motor ; seventh, from the motor to the compressor, and eighth, 
from the compressor to the drill. In the hydraulically compressed air plant under 



266 TRANSMISSION. 

the Taylor system we just have two transformation losses — first from the watef 
to the air in the receiving tank, and from the receiving tank to the drill. The 
Magog, Quebec, plant is actually running with an efficiency of delivered air of 62 
per cent., and Professor Nicholson, of McGill College, Montreal, in a very able 
treatise on the plant, shows that the efficiency should have been 81 per cent, instead 
of 62, the difference being largely accounted for by a loss due to ineffective sepa- 
ration, 20 per cent, of the air taken down having escaped with the up-cast water. 
This was due to the small capacity of the separating tank; and, as Professor 
Nicholson points out, "all future plants will avoid this loss, and we may expect 
as high an efficiency from this system as when the power is given off at a turbine 
jack-shaft, when it is not by any means in such a fit state for transmission as it is 
in the shape of compressed air." Professor W. C. Unwin, F. R. S., author of 
"The Development and Transmission of Power," says: "I expect that an effi- 
ciency of 75 per cent, can be reached when the proportions of the apparatus have 
been better adjusted. This comparatively large compressor (referring to the 
Magog plant), is therefore, an example of a very successful application of Mr. 
Taylor's system. It works almost automatically, and with very little supervision. 
It has no moving parts and nothing requiring adjustment, and the apparatus will 
cost very little for maintenance or repairs." 

We come now to consider the respective losses in both systems due to 
transmission. It is generally believed that electricity has a much superior ad- 
vantage over compressed air for transmission purposes, that is, that there is a 
much smaller loss of energy over electric wires than through pipe lines. Com- 
pressed air has been badly misrepresented in this respect; this loss has been 
greatly exaggerated, and the catalogues of air-compressing machinery companies 
have not improved matters any ; in fact, they have done more harm than good as 
regards the interests of compressed air. . The tables published in air compressor 
catalogues usually speak only of the loss of pressure ; they fail to tell us that the 
loss of pressure is not necessarily, or to the same extent, a loss of power. As 
Frank Richards, in his work on "Compressed Air," page 33, says: "The actual 
truth is that there is very little loss of power through the transmission of com- 
pressed air in suitable pipes to a reasonable distance, and the reasonable distance 
is not a short one. With pipes of proper size and in good condition, air may be 
transmitted say ten miles, with a loss of pressure of less than one pound per mile. 
If the air were at 80 pounds gauge or 95 pounds absolute upon entering the pipe, 
and 70 pounds gauge or 85 pounds absolute at the other end, there would be a loss 
of little more than 10 per cent, in absolute pressure, but at the same time there 
v/ould be an increase of volume of 11 per cent, to compensate for this loss of 
pressure, and the loss of available power would be less than 3 per cent. With 
higher pressures still more favorable results could be shown." As a competitor 
with electricity in long distance transmission, it seems almost like scientific heresy 
to claim for it equal if not greater efficiency; nevertheless the writer claims that 
within the 20-mile limit compressed air will compare in efficiency with electric 
transmission, while so far as operating and maintenance expenses are concerned, 
the electric proposition is not to be compared for a moment with that of air. 
Over 15,000 h. p. of mechanically compressed air is distributed to-day throughout 
the city of Paris, France, being transmitted from a series of stations from three 
to fifteen miles distant, with a loss of 10 pounds pressure in transmission. This 



TRANSMISSION. 267 

compressed air is used for all kinds of purposes ; and additional intallations are 
constantly being made to meet the ever-increasing demands. 

Professor W. C. Unwin in his work on "The Development and Trans- 
mission of Power from Central Stations," page 186, says: "In comparatively 
short distance transmissions such as those in towns, the loss of pressure in the 
mains is so insignificant that it may be neglected. In long distance transmissions 
an accurate estimate of frictional loss is necessary. The author believes that he 
has shown, using data derived from careful experiments on twenty miles of main 
in Paris, that long distance transmission of power by compressed air is perfectly 
practicable." In the work referred to Professor Unwin gives the figures on a 
10,000 h. p. plant, where the initial pressure is 132 pounds, and the transmission 
pipe is 20 miles in length and 30 inches in diameter, and shows that the loss of 
pressure in such a case would be only 12 per cent., which means a loss of power 
of less than 6 per cent. 

It is not the purpose of the present article to institute a comparison between 
the work done by mechanical air compressors and the Taylor air compressor, its 
object being to show the comparison of the latter with electric transmission. As, 
however, the mechanical compressor becomes a part of the system in the electric 
proposition, being necessary at the distribution end of the line to convert the 
electric energy into compressed air, this is the proper place to say a few words as 
to the relative efficiencies of the product turned out by the mechanical compressor 
and the Taylor air compressor respectively. The Taylor compressor turns out 
absolutely dry air — a feat which is impossible of accomplishment by any known 
mechanical compressor. The great advantages of dry air are sufficiently well 
known to all air users, so it will not be necessary to dwell on this point here. 
From the very nature of mechanical compressors, it will never be possible for 
them to turn out dry air. Owing to the rise of temperature which accompanies 
all mechanical compression, mechanically compressed air will always contain a 
higher percentage of moisture than the surrounding atmosphere; in this sense 
the mechanical compressor acts like a moisture collector, and this moisture is 
discharged and freezes up in the machinery upon the expansion of the air when 
used. From actual tests it is found that the Taylor compressor turns out com- 
pressed air which is three times drier than the free air of the atmosphere from 
which it is drawn. This may appear somewhat surprising, but it is nevertheless 
true. It leaves the compressing tank absolutely dry and cool, its temperature 
being the same as the water which it carries down. This is the ideal condition to 
which all compressed air users and manufacturers of air compressing machinery 
have been striving to attain, and particularly in its application to mining, where 
compressed air is required for constant use by the drills, will this advantage of 
obtaining absolutely dry and cool air be found to be an inestimable boon. 

4. — RELATIVE SIMPLICITY OF SYSTEMS AND THE SUPERIOR ADVANTAGES OF OPERATING 
WITH SIMPLE MACHINERY. 

In long distance electric power transmission the apparatus used is of a 
highly unstable character, necessitating as it does constant supervision by skilled 
men. The multiplicity of transformers, high potential insulators and other high 
potential devices in long distance electric propositions renders them exceedingly 
liable to break-downs, particularly if the transmission line passes through a rough 



268 TRANSMISSION. 

and wooded country. A break-down generally occurs just when the power is 
most wanted, and when the heaviest load is on. Trouble on the outside line from 
storms, falling timbers, lightning and other causes is immediately felt at the gen • 
crating station, with very often disastrous results to the high potential machines 
and apparatus. If by machinery ig implied moving mechanism, such as wheels, 
shafts, pulleys, belting, gearing, etc., then there is no machinery whatever involved 
in the Taylor system of air compression. There is not one single moving piece of 
mechanism in the whole compressing outfit. There is no other system of power 
generation in the world where these conditions exist ; and of all the factors which 
enter into the consideration of the economic production of the power at the 
present day, the one involved in moving machinery parts is the most important. 
The aim of modern machinery practice is to obtain the utmost possible simplicity 
of moving parts consistent with efficient operation. What does the absolute ab- 
sence of moving machinery mean in a system of power generation? It means 
the absolute elimination of all repairs and stoppages in the system; and those 
who have had to do with the management of power machinery can realize what 
this means from an economic point of view, and can also realize the trouble and 
annoyance dispensed with by the breaking down of moving machinery very often 
at the most critical times. In the Taylor air compressing system there is not a 
single moving axle or shaft, not a single moving wheel or gear, and not a single 
rod or piston of any kind. The system is, as stated, absolutely devoid of anything 
whatever in the way of moving mechanism ; and yet it develops and delivers any 
quantity of compressed air in a more efficient and perfect condition than if en- 
gines and compressors turned it out. 

UTILIZATION OF SMALL MOUNTAIN POWERS. 

There is one factor in this new form of hydraulically compressing air which 
will prove to be of great value in the utilization of the numerous comparatively 
small streams found in the mountainous mining districts of the west. It often 
occurs that in the course of a stream extending over a distance of five miles a 
series of falls can be obtained, aggregating about i,ooo feet, the stream gathering 
to itself as it flows downward additional supplies of water from various gulches. 
To improve these small powers by turbines involves, if the whole head is to be 
taken advantage of, the loss of the drainage area below the point of diversion, 
which ofttimes amounts to a large percentage of the whole, or the installation of 
three or four operating stations, the expense and maintenance of which make the 
power cost prohibitive. With the Taylor system every pound of water in the 
whole length of the stream can be used, because compressors can be installed at 
every few hundred feet, and the air generated by these compressors delivered into 
a common pipe line for distribution to the mining camp; or, in order to save 
expense in the sinking of shafts the upper compressors can make the air at a low 
pressure and this air can be carried to the lowest compressor, the lowest compres- 
sor being used as a "booster" to raise the pressure so that it can be economically 
transmitted. In this way the entire h. p. of the stream on every foot of its length 
can be utilized without any addition to the operating expenses and with only a 
comparatively small increase to the installation cost. The system in other words 
has all the elasticity of electricity with elimination of its operating and mainte- 
nance expenses, and the volume of air transmitted in the pipe line can be doubled 



TRANSMISSION. 269 

even after the compressors are built, by the construction of a second compressor 
to "boost" up the air made by the first compressor to a higher pressure. 

It will also be observed that the Taylor system is by far the more econom- 
ical in the use of water in the cases we have been considering; and this is an im- 
portant item with the mountain streams of the^ West, whose water supply is lim- 
ited, and for the use of which certain fixed charges are made by the Government 
according to the quantity used. Every year adds to the industrial value of the 
streams, and therefore any system of power development which involves the more 
economical use of the water is the system to which preference must be given. 

Compressed air is the ideal applied power and particularly is this the case 
under the Taylor system. The plant where is it installed is like a part of nature 
herself, the water being simply directed to flow through an iron or wooden pipe 
instead of through its former channel. There is practically no wear upon the 
system, and the power materials are drawn from nature's inexhaustible store- 
house. It is incomparable in its simplicity, and is destined to bring compressed 
air as an applied power to its deserved and proper place — the very front rank 
in the mechanical world — a consummation impossible of attainment with any 
known system of mechanical compression at the present day. 



DISCHARGE OF AIR FROM PIPES UNDER HEAVY LOSSES OF 

PRESSURE. 



BY WILLIAM COX. 



It is generally supposed that the volume of "air" discharged from a pipe 
increases with every increase of pressure absorbed in overcoming friction. Thus, 
if the initial pressure is 100 pounds, more air will be discharged with a final 
pressure of 80 pounds than with a final pressure of 90 pounds. That a limit to 
this useful absorption of pressure exists hardly seems to have been considered, 
except such limit as would be imposed by the extra consumption of fuel, etc. 
Yet upon due reflection it would almost appear natural that such a limit should 
exist; but why, where? The important question therefore arises: What, if any, 
maximum proportion of the initial pressure may in any given case be absorbed 
in overcoming friction in the pipe before this limit, if it exists, is reached? 

One great difficulty in dealing with all problems relating to the flow of air 
in pipes is that all the practical users of this valuable commodity always calculate 
according to volumes of free air. Now, free air does not circulate in pipes, does 
lot run rock drills, pumps, hoisting engines, etc. Hence much confusion of ideas. 
The supposition that free air flows through a pipe implies that there is in it con- 
stant volume, constant density and constant velocity of flow. But the fact is that 
jach of these is varying at every step of the current's passage. This general con ■ 
lideration of free air instead of compressed air leads also to the application to it 
>f laws which affect compressed air, whereas the laws governing free air and 
ompressed air, as specially related to flow in pipes, are in most cases entirely 
•pposite. 



270 TRANSMISSION, 

In order to have clear ideas on this subject, and to arrive at correct con- 
clusions, it is therefore necessary that we should deal with what actually flows 
through a pipe and is discharged from it. Thus, to return to the supposition with 
which this paper opens, that lOO cubic feet of air, compressed to lOO pounds 
gauge pressure, enter into a pipe per minute from the receiver, it would appear 
evident that with every subsequent reduction of the terminal pressure, or pressure 
of discharge or egress from the pipe, the volume of air (compressed) discharged 
will by reason of its expansion be greater and greater until the maximum reduc- 
tion of the terminal pressure (in this case lOO pounds) expands it to the point of 
free air, or air at atmospheric pressure, when its volume will also be a maximum. 
Such increases for a constant volume of compressed air, and for various reduc- 
tions of pressure would be as follows : 

100 cubic feet of air at lOO pounds gauge pressure is equivalent to 121 cubic 
feet at 80 pounds ; 153 at 60 pounds ; 209 at 40 pounds ; 330 at 20 pounds ; 464 at 
10 pounds and 780 at atmospheric pressure. 

As the volume increases therefore toward the outlet of the pipe, the velocity 
of flow must also clearly increase; and as the greater volume is under a lower 
pressure, its density must consequently be less, hence as stated, what flows 
through a pipe is by no means free air. 

The assumption, when applied to compressed air, that the volume of air dis- 
charged from a pipe increases with every increase of pressure absorbed in over- 
coming friction, is therefore, we may say, correct. The case given above does not, 
however, represent the flow of air in a pipe, as it supposes that the same volume 
of air enters the pipe, and consequently that the same equivalent volume of air, 
but at a lower pressure, is discharged from the pipe, whatever variations there 
may be of the terminal pressure. 

The laws governing the flow of air in pipes show that the discharge of air 
(compressed, not free) from a pipe varies as the square root of the loss of press- 
ure, when the diameter and length of the pipe and the initial pressure are con- 
stant. 

The formula for the flow of compressed air in pipes given by the writer in 
Compressed Air, January, 1898, page 359, is : 



jd^ X iPi—ps) 



Discharge in cubic feet per minute. = cA/ '" " j^"' (i) 

» M/J X t 

which may also be put in the form 

c Vd^ 

Discharge = -^= — -^ x Vp^p^ (2) 

f W -^ X r t 

The first factor on the right hand of this equation represents the diameter 
and length of pipe and the initial pressure, and if in any number of cases this is a 
constant quantity, then clearly the discharge of compressed air will vary as 
V Pi—P2,ov the square root of the loss of pressure. And examination will show 
that according to the formula there is no limit to this absorption of pressure 
until the air is discharged without pressure into the atmosphere. But then 
cut bono? Considerations, commercial, mechanical or scientific, or all combined, 
will find it essential that some limit to such wasteful absorption of pressure be 



TRANSMISSION. 



271 



imposed; and the cost of compressed air at its initial pressure, and its effective 
ralue at any given terminal pressure will be in a broad sense the factors which 
rill determine at what figure this limit shall be placed. 

In the example of the discharges given on page 270, supposing that 

c VW 



Vw^x Vl 



then we should have the following volumes of compressed air discharged at the 
different terminal pressures noted, namely: 

80 lbs. final pressure, 100 x 1/20=447 cubic feet. 



60 " " 


* 100x^^40=632 * 


40 ♦' " 


100x1/60=775 • 


20 " " 


' 100 X 1/80=894 ♦ 


10 " " 


* 100 X y'9o=949 ' 


Atmospheric 


* 100 X 1/100=1000 * 



But on page 270 we see that 100 cubic feet of air at 100 pounds pressure is 
the equivalent of 780 cubic feet of free air. Now, if the air were at atmospheric 
pressure at the exit or in the nozzle of the pipe, it would not flow out of it, as the 
front and back pressures would balance each other, and the whole volume of air 
in the receiver would remain there, being balanced by the pressure absorbed in the 
pipe to overcome the enormous friction produced by the great velocity of flow at 
the end of the pipe. To force it out, therefore, the pressure in the receiver would 
have to be increased, and likewise the initial pressure in the pipe, which would 
then be shown by a somewhat increased volume of i/^i in Eq. (2). 

Or may it not be that if the pressure in the receiver is kept constantly at 
100 pounds, that a somewhat less quantity of air would be discharged from the 
pipe than 1,000 cubic feet? Unfortunately in this examination we have only a 
theoretical expression of the laws of nature, in the shape of a formula, to guide 
us, and no series of data based upon actual experiments to help us. 

This is, however, taking a very extreme case, where such refinements of 
calculation would probably never be required, and also one to which perhaps the 
formula, although an excellent one, may not apply. But it must be remembered 
that the formula does not deal with the quantity of air that enters into the pipe, 
but only with what is discharged from it. The first factor on the right hand of 
equation (2) does not indicate what volume of air would enter the pipe except 
theoretically upon the supposition that no friction whatever exists. It is only 
when in conjunction with the second factor that the volume of air discharged is 
obtained. It may, therefore, be that the real discharge at atmospheric pressure 
would be 1,000 cubic feet, as also at 90 pounds final pressure 949 cubic feet, and 
so on. 

D. K. Clark, in his work on the steam engine, says: "The flow of steam 
of a greater pressure into an atmosphere of a less pressure increases as the dif- 
ference of pressure is increased, until the external pressure becomes only 58 per 
cent, of the absolute pressure in the boiler. The flow of steam is neither increased 



* This Ib correct for a 3-inch pipe, 144 feet long, with Pi =100' pounds. 



272 TRANSMISSION. 

nor diminished by the fall of the external pressure below 58 per cent, of the inside 
pressure, even to the extent of a perfect vacuum." 

Is it not possible that some such law may be found to exist in the case of 
compressed air ? Be this as it may, the formula seems to show that the discharge 
of compressed air continues to increase with every successive reduction of the 
final pressure, or increase of pressure absorbed in friction, although this increase 
of discharge is a continually decreasing one in proportion to the increase of 
pressure loss. Thus for 20 pounds loss of pressure, from 80 to 60 pounds final 
pressure, there is an increase of discharge of 185 cubic feet, whereas for 20 pounds 
loss of pressure, frcm 20 pounds final to atmospheric pressure, there is a gain of 
only 106 cubic feet. 

But what interests the compressor builder and, in accordance with the way 
he has been educated, the compressed air user, is the amount of free air which is 
supposed to be discharged from the pipe. The compressor builder and user figure 
only on free air because the compressor at the very commencement of the cycle 
of operations for which air is to be used, takes in free air, and its dimensions, 
speed, etc., have all reference to this quantity of free air taken in. So, further 
on in the cycle of operations, the builder calculates that a given quantity of free 
air will be required to run a certain number of rock drills, or a hoisting engine, 
or a pump, or to perform some other work. Therefore as much as possible the 
views of the builder and user have to be met. That form of the formula which 
deals with equivalent free air will therefore now be examined. 

Some time ago I was asked to solve the following problem : 

What volume of free air will pass through a 3-inch air line, 0,000 feet long, 
the initial air pressure being 125 pounds and the terminal 80 pounds? Also how 
much will pass if the terminal pressure is 60 pounds, other conditions remaining 
the same? 

Here, then, we have the following data to work from: 

3 inch pipe, ^^^"=876 
6,000 feet, Vl =77.46 
125 pounds pressure iOj =0.7230, and ,r'i^i=o.85 



80 pounds final pressure =P2, thenp^ — ^^2=45 lbs., and Vp^- p.^=6.ji 
Also 60 pounds final pressure = P2, then jj^ — ^2 = 65 lbs., and Vpx — ^2 = 8.06 
Now, inserting these in equation (2) we get in the first* case 

O—fl 

Discharge of compressed air in cubic feet per minute = — ^ — x 6 71 

0.85x7746 
= 13.3x6.71 

=89.243 cubic feet air at 80 pounds terminal pressure, 
and in the second case 

q— /T 

Discharge of compressed air in cubic feet per minnte = —^ — 7 x 8.06 

^ 0.85x77.46 

= 13.3 x 8.06 

= 107.198 cubic feet air at 60 pounds terminal pressure. 

To find the equivalent in free air of any volume of compressed air we have 

Equivalent free air = Compressed air x — ^ (3) 

where G is the gauge pressure of the volume of compressed air. 



TRANSMISSION. 273 

The writer has simplified this by reducing it to the form. 

f=^=^+o-^P (4) 

where / is a factor to reduce compressed air at pressure p to its equivalent volume 
of free air. 

Inserting the values of p2 in Eq. (4) we get for terminal pressure 80 pounds 
^ = I + (0.068 X 80) = 6.44 
and for terminal pressure 60 pounds 

A — I + (0.068 X 60) = 5.08. 

Equation (3) may now be put into the form 

Equivalent free air = Compressed air x /g (5) 

which gives us in the first case for 80 pounds final pressure, 

Discharge of freaair=89.2 x 6.44=574 cubit feet per minute, 
and in the second place for 60 pounds final pressure, 

Discharge of free air=io7.2 x 5.08=544 cubic feet per minute. 

It results, therefore, that with a reduction of the final pressure by 20 pounds, 
we actually obtain a smaller discharge of equivalent free air, although, as already 
shown, we have a larger output of compressed air. And how do we know that 
with 80 pounds final pressure we do not obtain a smaller discharge of equivalent 
free air than we should do with a final pressure of 90 pounds? In other words, 
Where is the limit? What is in any given case the Lowest Useful Final 
Pressure.? This is a very important point for the compressor builder and for the 
compressed air user, who always calculate on the basis of free air. It is shown 
by the solution of the above problem that with very heavy losses of pressure in a 
pipe line, a smaller equivalent volume of free air can be forced into the pipe than 
with more moderate pressure losses, the initial pressure remaining the same. 
How many pipe lines have given results below what was expected, through 
ignoring this fundamental principle, and how often has the cause for the failure 
been accounted for in any way but the correct one? 

Combining equations (i) and (4) we now obtain the following general 
formula for the discharge of equivalent free air from pipes : 



— -/s ^ VP\ — P2 
Discharge free air in cubic feet per minute = C\/d^ z:^ =- (6) 

In those cases (such as the problem under consideration) where the 
diameter and length of a pipe, as well as the initial pressure, are constant, and 
the final pressure only varies, the formula may be put 






Discharge free air in cubic feet per minute = I -^i z\ ^ if 2 ^ VPi—Pi) C^) 

it being then at once seen that as the first factor on the right hand of the equation 
is constant, the discharge of equivalent free air varies exactly in proportion to 



if 2 X VPi—P2h 
that is, in a certain degree, according to the final pressure. By this arrangement 
of the formula we are enabled to examine easily the effects produced upon the 
discharge by variations of th? final pressure, as the only factor with which we 



274 



TRANSMISSION. 



have to deal is the second one on the right hand of equation (7). By calculating 
values of 



if 2 X VP1—P2) 
for a number of terminal pressures in a given case, we can at once and easily 
campare them, and select a limit which should not be exceeded in order to obtain 
results such as may be desired. 

And here it is important to note that as p^ increases in value, f^ decreases 
in value, and vice versa, so that there must be a point at which the value of 

/s X i/Pi— Ps 
is a maximum, and consequently the discharge of equivalent free air from the pipe 
is also a maximum, and any further pressure absorbed in friction beyond this 
maximum value of p-^ — pi or minimum value of p2, produces a diminution of the 
discharge, which is absolute loss of economy. 

Suppose an air compressor to be rated to compress 574 cubic feet of free 
air per minute to 125 pounds, and that this air is forced through a pipe of such 
diameter and length that the terminal pressure is 80 pounds. Now, if that 
terminal pressure is reduced to 60 pounds, the compressor will only have to com- 
press 544 cubic feet of free air per minute to 125 pounds, so that it is not working 
up to its full capacity by 30 cubic feet a minute, or more than 5 per cent. And yet 
who will affirm that the real work done by the compressor is not as great in one 
case as in the other? 

What is in any given case the Lowest Useful Final Pressure, and how is it 
ascertained? 

Taking the problem before us, and leaving out of consideration the factor 






which has no effect upon this question of final pressure, let us take a few different 
fmal pressures and tabulate them thus : 



TABLE 25. 





P2 


/; 


Pi—P-i 






Pi 


VPi—p-i 


f-z X VP1—P2 


lbs. 


lbs. 




lbs. 






125 


85 


6.78 


40 


6.3246 


42.88 


125 


80 


6.44 


45 


6.7082 


43.20 


125 


'75 


6.10 


50 


7.0711 


43.13 


125 


70 


5.76 


55 


7.4162 


42.74 


125 


65 


5.42 


60 


7.7460 


42.00 


125 


60 


5.08 


65 


8.0623 


40.94 



TRANSMISSION. 



275 



Here we see that the maximum value of 



is somewhere about where p2 = 80 pounds that is, in any case, when the value of 
p2 lies somewhere between 75 and 85 pounds. It may be more or it may be less 
than 80 pounds. We, therefore, now tabulate a little further as follows : 

TABLE 26. 





P2 


/. 


P1-P2 






Pi 


VP1—P2 


/s X VP1-P2 


lbs. 


lbs. 




lbs. 






125 


82 


6.576 


43 


6.5574 


43.1215 


1Q5 


81 


6.508 


44 


6.6332 


43.1689 


125 


80 


6.440 


45 


6.7082 


43.2008 


125 


79 


6.372 


46 


6.7823 


43.2168 


125 


78 


6.304 


• 47 


6.8557 


43.2183 


125 


77 


6.236 


48 


6.9:82 


43.C043 



From this we see that the highest value of 



A VP1—P2 
is 43.2183, which is obtained when the terminal pressure is 78 pounds. This is 
then the limit sought, or the lowest useful final pressure for an initial pressure of 
125 pounds. For other initial pressures the limit can be found in the same way. 
It must be admitted that it is somewhat tedious, but the result in any given case 
may far more than compensate for the time and labor bestowed. The writer has 
worked out these limits for a full range of initial pressures from 10 to 1,000 
pounds. 

Applying now the limit of 78 pounds, as found above, to the problem under 
consideration, we have by inserting the known values in equation (7) 
Di^ch rge of free air in cubic feet rer minute = 13 3 x 43.2183=574.80 cubic feet. 

The exact discharge for 80 pounds terminal pressure is 43.2008 X 13.3 =f 
574-57 cubic feet. The difference is so slight that 80 pounds may be practically 
considered as the lowest limit beyond which, for the sake of economy, the terminal 
pressure should not be allowed to fall. 

From a careful consideration of this prolilem it will be evident that all use 
of (he simple term "air" should be accompanied by a clear comprehension of what 
is meant, and what it involves. Confusion may lead to serious consequences. 

Viewed in the light of what is here shown it would be both interesting and 
profitable to reduce the volumes of comjircssed air given on page 271 to their 
equivalent volumes of free air. A certain point will then probably be found which 



276 TRANSMISSION. 

is not the "lowest useful final pressure," but rather the most economical one, when 
the cost of the compressed air at its initial pressure and the amount of effective 
work which may be obtained from it at terminal pressure are duly considered. 



LOSS OF LOADS IN AIR-PIPES.* 



STATE OF THE QUESTION. 

A great many authors have dealt with the loss of energy sustained by a cer- 
tain volume of air in its passage through metal pipes; but the coefficients pub- 
lished, correct enough when applied to the pipes experimented with, no longer 
hold good when extended to those of sheet-iron or tin-plate, and there is great 
interest in determining the constants to be introduced into the general formula 
expressing loss of load in the air-pipes used in mines. The author's method of 
experimenting was suggested by the remarkable labors of M. Murgue, who in the 
Bulletin of the Societe de ITtidustrie Minerale, has shown in such a striking 
manner the influence exerted by the nature of the sides on the resistance opposed 
to the air's motion through mine workings ; and the former's researches, which 
may be regarded as the complement of M. Murgue's, permit of solving beforehand 
with sufficient exactitude the problem : 

"Calculate the energy necessary to draw through a line of pipes, included in 
a given circuit, a given volume of air for ventilating the face of a heading;" or 
inversely, "Given a pipe line of known length, nature and dimensions, forming 
part of a circuit, calculate the air volume that will be drawn to the face by a 
given power." 

MODE OF EXPERIMENTING. 

The time-honored formula expressing the loss of load due to the motion of 
air through pipes is 



h = a s "2 
in which o is a coefficient varying with the nature of the sides, L the length of 
the pipe, t> and s the mean perimeter and sectional area, v the mean speed, and rJ 
the density of the air ; and generally the numerical value given to a depends upon 
a depression (water-gauge), /?, expressed in millimetres (say inches) or kilo- 
grammes per square metre (say pounds per square inch) of surface. Finding 
the value of coefficient a, that characterizes a pipe of known form and dimensions, 
is connected with a simultaneous determination of the motive depression, h, pro- 
ducing a current of mean speed, v; and the following are the instruments that 
were used in the author's experiments, with the methods employed for measuring 
the intensity of the air-current and the loss of load corresponding with a given 
distance passed through. 

Pressure-gauge. — The remarkably correct instrument used by Mr. Murgue, 
and lent by M. Marsaut, which permits of reading a difference of level correct to 

*From a papfir by M. Paul Petit, Chief Engineer of the Saint-Etienne Collieries. Loire, France, 
prepared for the International Congress on Mining and Metallurgy, held in connection with the Parie 
Exhibition. 



TRANSMISSION. 277 

within one hundredth part of a millimetre, consists essentially of two glass flasks 
of very different diameters, connected below by an indiarubber tube. It is only in 
the small flask that the difference of level due to the diminished pressure is ob- 
served, and that with the aid of a microscope, the simultaneous fall of the water 
level in the large flask not being regarded ; and the result of the readings is cor- 
rected by calculation. The great sensitiveness of this instrument requires that it 
be placed on a strong and massive table, for preventing the water-level from be- 
ing influenced by trepidations ; and, for experiments on the surface the pressure- 
gauge was placed on a thick surface (setting-out) plate, while a portable cast-iron 
table was made for receiving the instrument in the underground workings. 

Anemometers. — For measuring the air volume drawn along by a known 
depression three small Casartelli, anemometers were used, M. Murgue's ingenious 
method of instantaneously throwing the wheel in and out of gear being adopted. 

Atmospheric Observations. — The temperature of the air-current was meas- 
ured above and below each line of pipes experimented with, or each length of 
underground road, by thermometers graduated to one-tenth of a Centigrade de- 
gree; the pressure being read off from an aneroid barometer; and the humidity 



E^ 



G 

FIG. 86. 

in the atmosphere was taken by a very correct hygrometer, the weight of air in 
motion being calculated by the convenient tables appended to the work by Herr 
Althans, president of the Prussian sub-committee on ventilators. 

Air-pipes. — In the first series of experiments sheet-iron pipes of 27 mm. 
(i 1-16 in.) inside diameter with screw socket connections were used; but, owing 
to their joints not being found tight notwithstanding every precaution, lead pipes 
of 17 mm. (21-32 in.) inside diameter and 3 mm. (% in.) thick, soldered together 
if necessary, were used for the second series — that metal, which affords absolute 
tightness, being suitable on the surface where these experiments were made, al- 
though its softness would be an objection under ground. 

Production of the Air-current. — The various lines of pipes experimented with 
were in turn laid out in the yard of the workshops, near the boilers; and an ex- 
hausting fan at the down-stream end set up an air-current, the intensity of which 
could be varied at pleasure. For straight lines of pipes a Rateau fan of 70 cm. 
(2 ft. 3 in.) diameter, driven directly, was used; but in subsequent experiments, 
for obtaining more intense currents, and consequently greater difference of pres- 
sure than could be more correctly measured by the gauge, a Mortier diametral 
fan of 90 cm. (2 ft. 11 in.) diameter and the same width, also driven directly, 
was utilized. The trials with curved lines of elliptic pipes and those of large 
diameter were made in the locomotive running-shed, an arrangement which per- 
mitted of the experiments being continued uninterruptedly in all weathers. 

Measuring the Air-current. — The annexed diagram, Fig. 86, shows the gen- 
eral arrangement adopted, in which the pipe, C D, to be experimented with is 
inserted between two adjutages, B C and D E, the former receiving the air-cur- 



278 



TRANSMISSION. 



rent drawn in by the fan through a convergent inlet-piece, A B, while the latter 
delivers it to the exit-piece, E F, also convergent, connected with the fan inlet, G. 
The adjutages, and also the inlet and the outlet, are made of ploughed and 
tongued boards, carefully fitted; and the air volume was measured near the inlet 
and outlet in the cross-sectional plane of their adjutages. The gauging station was 
placed at such a distance from the inlet and outlet of pipe C D that the flow might 
be considered as taking place by parallel currents, uninfluenced by the contraction 
due to the air's motion, between the larger sectional area of the adjutage and the 
more or less reduced sectional area of the pipe experimented with. By simul- 
taneously measuring, in the entrance and exit adjutages, the air volume passing 



B- 




c 






As*'' ^^ 

1 J 


r> 




c 




'• '-^'"""r^'i 




-I 1 - ' -t- 




A 


^Lli..l. 


r> 



M- M 



FIG. 87. 



at each of the stations, it was possible to estimate the quantity of air infiltration 
and check the degree of tightness in the whole arrangement. 

In all the series of experiments the sectional area of the adjutage D E re- 
mained practically constant; and the inlet with its adjutage was adapted to the 
size of the pipe to be experimented with. As the energy that could be set up by 
the fan was limited, it became necessary, for measuring the volumes of relatively 
slight intensity circulating through pipes of small diameter, to reduce the sec- 
tional area of the inlet adjutage to the value corresponding with a speed of cur- 
rent that could be exactly measured by the anemometer. The connection of the 
various pipes with the entrance and exit adjutages required great care, for avoid- 
ing the infiltration of air that might escape being registered by the anemometer, 
and thus falsify the measurements of the volume; and on that account the pipes 
were allowed to project slightly inside each adjutage so as to bear against parti- 
tions, carefully constructed of thick boards ploughed and tongued, forming part 
of the adjutage, luted with putty and having an aperture of the same diameter as 
the pipe. 

For measuring by the anemometer the intensity of an air-current passing 
through pipes so small as those experimented with, a difficulty arose that does not 
present itself in the gauging of mine workings; and it is evident that the dimen- 



TRANSMISSION. 279 

sions of the entrance adjutage cannot be too much increased without a risk of 
excessively diminishing the speed of a weak air-current. Now, for a moderate 
section of adjutage the presence of an experimenter may greatly invalidate the 
observations ; and it would become impossible to simultaneously measure the air 
volume passing through the pipe and the depression of the current. For getting 
over this difficulty, the following arrangement, due to Herr Althans, was adopted : 

Referring to Fig. 87, the rectangular sectional area of the gauging station was 
represented full size by a tablet. A' B' C D' placed above the adjutage, A B C D, 

and divided into the squares, i, 2, 3 17 and 18 corresponding with the 

anemometer stations. A slot, a b, was made in the top cover, B C, of the ad- 
jutage, and closed by a wooden slide, moving with easy friction in a guide 
screwed to the cover, the minimum travel being equal to double the width, B C, 
of the adjutage. In the movement from left to right or from right to left given 
by hand to this slide, its extreme positions will be M N and M' N', the mean 
position being M" N" ; and at no point of its travel can there be penetration of 
the outer air into the inside by the slot a b, which is constantly covered by the 
moving slide. 

As shown in Fig. 88, the anemometer being hung from the end of a small but 
rigid rod, of such a length that if one of its ends occupies point i (see Fig. 87) in 
the upper tablet the other will occupy station No. i of the adjutage, it will pene- 
trate into the interior through a hole in the slide. If the slide is at rest, all that 
will be required is to lower in a vertical direction the upper end of the rod, bring- 
ing it in succession opposite stations i, 6, 7, 12, 13 and 18 of the tablet, for the 
centre of the anemometer to occupy the corresponding stations ; and if the instru- 
ment is to be displaced horizontally it will be sufficient to move the slide in the 
proper direction by maintaining it at a station for a preconcerted space of time, 
after the manner of a pantagraph, although in this case there was no reduction 
or enlargement. 

In order to permit of throwing the anemometer in and out of gear from a 
distance without entering the chamber, it was hung from the end of a light but 
rigid copper tube; and a copper wire inside the tube was held by one of the ex- 
perimenters standing on the adjutage opposite the numbered tablet, a spring fas- 
tened to the stand of the instrument acting through a small chain on the engaging 
lever to which the wire is attached on the side .opposite the spring. When the 
wire is stretched the anemometer is thrown into gear, but at other times the 
spring, acting on the lever, throws the instrument out of gear, an arrangement 
that gave every satisfaction. 

In 1897 each series of observations made on a given pipe was preceded by a 
gauging that comprised measurement of the speed at each of the eighteen stations 
marked on the tablet, one minute being occupied at each. During this protracted 
gauging the fan's speed was kept perfectly constant ; and, for taking into account 
slight variations in the engine, speed, the fan revolutions were taken simultaneous- 
ly with the gauging, the speeds observed being all reduced to a given fan speed 
supposed constant. The experiments following the first of each group only 
comprised a gauging for one minute each at three points in the sectional area ; 
and the total number of revolutions made by the anemometer during this space 
of time was registered. In accordance with M. Murgue's remarks as to the con- 



28o 



TRANSMISSION. 



stant ratio between the mean speed of the air-current for the whole of the sec- 
tional area and its speed at three given points, the result was arrived at by a 
simple proportion sum. 

In 1898 this manner of making the observations was modified for the fol- 
lowing reasons : The prolonged gauging before beginning each group of experi- 
ments took up too much time for recording so many observations as those re- 



Elevatian 




^^^i^^fP^^^W'^^^m^i 




^^^^^^^^^^^^^^^^^^^^WW^^^W 



ff^^km^ 



Wf^^ 





-n 


J 




Plan 








'fe 


1 






i 


? 




••: 




-- "■•! 


! 




s.; 


U 






"^ ■ ■■ 


; 




. 


rr=— - — — ■ ' — ' ' — ' 


1 




FIG. 88. 









quired; but the chief reason consisted in the difficulty of keeping the fan at a 
constant speed, especially when setting up a comparatively high watergauge, the 
boiler though fired hard, not being able to make sufficient steam. 

There are, however, grounds for believing that the second method was quite 
as correct as the first. One permitted, which could not be obtained with the 
other, of tracing curves of equal speed ; but this advantage was slight, because a 



TRANSMISSION. 281 

knowledge of the distribution of the different speeds is only useful if it relates 
to the pipe experimented with, and the gauging was effected in an adjutage the 
sectional area of which was always far greater than that of the pipe. The time 
during which the anemometer was kept at each station has never been less than 
six seconds, which is considered sufficient by all who have taken up this ques- 
tion; and the rectangular form of the adjutage, 1.5 m. by 0.75 m. (4 ft. 11 in. by 2 
ft. sH in.) lends itself readily to a division into equal squares, their centres cor- 
responding with the stations. 

Influence of Air Infiltrations. — However carefully the joints be made, it is 
difficult to entirely avoid the errors resulting^ from slight air infiltrations over the 
distance with respect to which the loss of load is to be measured ; but for reducing 
this cause of error to a minimum the author made a point, before beginning each 
series of observations, of gauging the entrance and exit adjutages at the maxi- 
mum fan speed, so as to better appreciate the extent of the leakage, although with 
metal pipes an almost entire concordance between the inlet and outlet volumes 
was attained. 

TAKING THE WATER-GAUGE. 

In all the observations made under the author's superintendence, the differ- 
ence of the total pressure was measured by two Pitot tubes placed along the 
centre line, the pipe facing the air-current; and here began the difficulties. 
These tubes ought to have been placed at the points of the stations, up-stream 
and down-stream, where reigned the mean speed ; but this was not done, for want 
of time, the tube being always held in the middle as if the total pressure were the 
same over the whole sectional area. The Murgue apparatus was set up, at the 
up-stream end, on one of the side faces of the air inlet ; and a slight shelter pro- 
tected the pressure-gauge arranged on the heavy cast-iron plate already men- 
tioned. Indiarubber tubes from the cocks connected the pressure tubes above 
and below with the large and small flask of the gauge respectively. In the ex- 
periments on pipes of slight diameter these tubes were laid along their length 
entering at two points comprising between them the length to be observed; and 
the two tubes were bent to a right angle so as to constitute a Pitot tube. 

Referring to Fig. 89 in the observations on straight pipes, the tubes, T T', 
starting from the Murgue pressure gauge, proceeded one to the up-stream sta- 
tion, A, and the other to the down-stream station, B, F being the fan and the ar- 
row showing the direction of the current. In the observations on separate 
straight portions connected by various bends the tubes might be arranged so as 
to permit of measuring at will the total loss of load, as well as the partial loss of 
load in each portion of the pipe line; and it is thus that, in the case shown by 
Fig. 90, the water-gauge may be taken if desired between the points i and 4 of 
the total distance traversed, or between the points 2 and 3 of the partial distance. 

CONDUCT OF THE OPERATIONS. 

The six observers were placed — the first near the exhaust fan for recording 
its speed; the second on the top cover of the up-stream adjutage facing the tablet 
above mentioned, for moving (as has been described) the rod of the anemometer, 
which he threw in and out of gear from a distance ; the third moved horizontally, 
from left to right and from right to left, the slide covering the upper slot of this 



282 TRANSMISSION. 

adjutage, and the fourth, holding a chronometer, gave the signals for beginning 
and finishing the observations, while the fifth and sixth respectively took the 
water-gauge and booked the number of revolutions made by the anemometer. 
The extreme stations, up-stream and down-stream, were connected by electric- 
bell apparatus, so that the signals agreed upon could be exchanged. 

So soon as the fan acquired the determined speed, the down-stream observer 
notified those up-stream; and at a stroke from the bell the anemometer was re- 
leased and moved about in the different stations, where it was kept for a given 
number of seconds signaled by the chronometer man; and during this time as 
many readings as possible (at least ten per minute) were taken of the depression. 
At the end of the observations the operators formed into two groups, each read- 



*^ 



T T' 



FIG. 



ing in turn the tachymeter and anemometer figures, this checking of the obser- 
vations, strongly recommended by M. Murgue, being indispensable for avoiding 
errors. 

GENERAL FORMULA EXPRESSING LOSS OF LOAD. 

After describing the numerous experiments with both straight and curved 
pipes, carried out in the above-mentioned manner, and quoting Herr Althans' 
simple formula for expressing loss of load, the author states it as follows : 

li = 0-0007489 X - /' , 61'i)-^ (1) 

h being the loss of load, L the length of pipe, D its diameter, (^ the weight of a 
cubic metre of air, and 7/ the mean speed of the fluid. He was able, thanks to the 
many and various observations made, to determine the true power which con- 
nects the loss of load with the mean speed, finding it equal to 1.916. As regards 
only the passage of air through pipes used for ventilating preparatory workings, 
a case which supposes for (\ a value near upon 1.2 kilogr. (3 lb.), he feels justi- 
fied in stating a = i ; and he was led empirically to modify the formula to the 
following: 

7. = 0-000765 X 33-^ ^5 1,^ ^^' (2) 

A table is given (in the original paper) of the values calculated by formulae (i) 
and (2) with the experimental results obtained for a whole series of diameters 
comprised between 0.259 and i metre; and a comparison of these values leads 
to the following 

CONCLUSIONS. 

I. For slight diameters the non-concordance between the calculated and ob- 
served results is sufficiently marked, and more so with the Althans formula (No. 
i) than with that proposed by the author (No. 2). 



TRANSMISSION. 283 

2. For pipes rough inside, such as those of 0.45 m. (i ft. 6 in.) and double 
that diameter, comparable with the state of a cast-iron surface, the Althans for- 
mula expresses the results observed with very slight divergence; but for smooth 




FIG. 90. 

pipes of galvanized sheet iron or painted with red-lead, and having a diameter 
larger than 0.338 m. (i ft. i in.), it gives the loss of load as rather high. 

In fine, the author considers that the general formula proposed by him em- 
braces the collective results with a very near approximation. 



COMPRESSED AIR FOR TRANSMISSION OF POWER.* 



By J. H. RONALDSON. 



The transmission of power, to a greater or less distance, is frequently a 
subject for the serious consideration of a mining engineer, and thanks to the 
advances in scientific and mechanical knowledge made during recent years, the 
choice of method is varied and the possible efficiency is considerable. The means 
of transmitting power are steam, water, wire rope, electricity and compressed 
air, and the advantages and disadvantages of each of these systems vary with the 
distance to be bridged and the conditions attending their application. 

Steam. — Within moderate distances and under certain conditions, steam 
is at once the most economical and satisfactory means of transmitting power, 
but the limitations to its use are too familiar to require enumeration. 

Water. — There is no more valuable agent than water for actuating hoists 
and for certain pumping operations in mines, where excessive lifts over long 
distances have to be overcome. One of Moore's pumps has been in use at South 
Bulli Colliery, Illawarra, for some years. 

Wire Rope. — For the general purposes of haulage, wire rope transmission 
of power is unexcelled, and it has in many instances been used for other pur- 
poses, such as pumping in mines. For the latter purpose it has, however, 
received a limited application, a result due, it is to be feared, to defective instal- 
lation, through a frequent ignorance of the properties of ropes and pulleys. 
When one remembers the admirable work done in the way of haulage, pure and 
simple, by modern ropes, it is inconceivable to think that this method could not 
be applied to pumping in mines, in many instances with favorable result. As an 

* A papLM- roKl hofore the New South Wales Chamber of Mines, June, 1900. 



284 TRANSMISSION. 

example it may be mentioned incidentally that at the Metropolitan Colliery in 
New South Wales, a band rope of crucible steel i]4 in. diameter, taken down 
a shaft 1,100 ft. deep, and transmitting at least lOO-horse power regularly for ten 
hours per day, worked without change for five years and was then only taken 
off to insure perfect safety in an important service. The rope was far from 
being worn out when changed. 

Electricity. — As a competitor with compressed air, electricity occupies the 
first place. Its use as a means of transmitting power has of recent years been 
widely extended, and in mines we have it now applied to pumping, haulage per 
medium of locomotives, and fixed rope haulage engines actuated by electricity, 
winding above and below ground, to rotary and percussive drilling, and most 
successfully to coal cutting machinery. 

Compressed Air. — For the transmission of power this agent has there- 
fore in certain directions serious competitors, in favor of which there has fre- 
quently been urged greater economy in first cost, in working cost, in efficiency 
and in applicability. These claims have, however, been keenly contested by the 
advocates of compressed air who, on the other hand, contend that it supplies a 
means of power transmission at once safe, economical and efficient for general 
mining work. The force of this contention has been much increased by the 
improvements effected during the last twenty-five years, in the methods of 
generating compressed air and of using it, as will be shown later on. There is 
little need to dwell on the importance of compressed air as a factor in the eco- 
nomy of many mines, an enumeration of its uses making this sufficiently appar- 
ent. It is used to actuate rock drills, underground haulage and hoisting engines, 
pumps, underground ventilating fans, Korting's air injectors, and coal cutting 
machines. It is necessary to an intelligent appreciation of the subject to con- 
sider the laws relating to air as a gas, and the mechanical causes which render its 
economical use more difficult than would at first sight appear. It is proposed, 
therefore, to consider the subject in the following order: — (i) The laws affecting 
the compression of air; (2) the various styles of compressors; (3) the causes 
of low efficiency in air compressors; (4) air conduits; (5) methods of using 
compressed air; (6) dangers attending its use. 

I. — LAWS AFFECTING THE COMPRESSION OF AIR. 

Air is an elastic fluid which, when free from vapor, behaves as a perfect 
gas ; 13.09 cubic feet at ordinary atmospheric pressure, and at 60 degs. Fahr., 
weighs I lb. According to Boyle's law, the volume of a gas varies inversely as 
the pressure affecting it so long as the temperature remains constant ; conse- 
quently in doubling or trebling the pressure the volume becomes one-half or one- 
third respectively. According to Charles' law, if the volume of a gas be kept 
constant, the pressure varies as the absolute temperature, and if the pressure be 
kept constant the volume varies as the absolute temperature. By the law of 
the transmutation of energy, work performed on a body, whether solid, liquid or 
gaseous, is evidenced by a definite increase of temperature in that body, and we 
are familiar with that fact as shown in the simple laboratory experiment of 
exploding a small charge of guncotton in a strong glass cylinder through the 
rapid heating of the air contained in it by a sudden jerk of a tightly fitting 



w^: 



TRANSMISSION. 285 

pi§ton. Consequently when air is compressed it is heated; when heated it ex- 
pands and the volume of air to be compressed is proportionately increased with a 
corresponding expenditure of the power required to compress it. Could the 
temperature of the air undergoing compression be kept constant (isothermal) 
during the process, and the heat taken up from it returned to the air during its 
expansion in the motor while doing work, all loss from this source would be 
avoided. This, however, is impossible, and the aim of modern compressors is to 
prevent an increase in the volume of the air by keeping down the temperature 
during the period of compression; that is by approximating to what is termed 
the isothermal process. It is clear that the least efficient compressor is the one 
in which no provision is made for cooling the air during the actual period of 
compression, that is one working on what is termed the adiabatic process. 

2. — AIR COMPRESSORS. 

Although compressed air had been used to a small extent previously, it 
was not till 1850, when the Mont Cenis tunnel was constructed, that its use be- 
came general. Two forms of compressors are in use, in each of which a reduc- 
tion of the temperature of the air is aimed at ; in one case by the use of a liquid 
piston in the cylinder, and in the other by a water-jacket round the cylinder, 
or by an internal spray of water. The former is termed a "wet" and the latter 
a "dry" compressor. 

Wet Compressors. — Of these, there are two types: (a) where the water 
piston owes its energy to the fall of water from a height; (b) where the water 
piston is actuated by a steam driven piston. At Mont Cenis, Mons. Sommeiller 
made use of water with a fall of 86 ft., and by utilizing the momentum of the 
falling water he was able to obtain an air pressure of 75 lbs. per square inch. 
Though extremely low in efficiency (not more than 6 per cent.) and necessitating 
clumsy plant, the arrangement gave results sufficiently good. This principle has 
been applied in other cases, and one arranged by Hathorn, Davey & Co., Leeds, 
was successfully used for many years in Mexico. The application of the prin- 
ciple is simple, and where an abundant water supply exists, excellent results are 
obtained. The second form of wet compressor has attained a wide application 
on the continent of Europe where, particularly among the highly educated Bel- 
gian and French engineers, the principles of air compression are more thoroughly 
understood than in Britain. It is, however, a question if their adherence to this 
method is not an instance of the length to which a desire to reach an ideal per- 
fection may lead one from the best practical solution of a problem. As will be 
shown later on, the dead space at the end of the air piston stroke is undesirable, 
and it was largely to eliminate this defect and to keep the air cool that liquid 
pistons had such a vogue on the Continent. The water forced back and forward 
in the cylinder and up the pipe at each end, carrying the necessary valves, filled 
the dead space. But unfortunately for this ideal, there are a number of incon- 
veniences attendant on the system. The cooling of the air is insufficient be- 
cause it is only on the surface of the water. The speed of the piston is extremely 
limited and cannot exceed forty to fifty feet per minute, on account of the mass 
of water to be moved; consequently the number of compressors required for a 
given work is large. The water agitated by the motion is frothed and causes an 



286 TRANSMISSION. 

excessive moisture in the air. Various devices more or less successful have been 
used to lessen these defects, but, in spite of all, the fact remains that in other 
countries these compressors have not found favor. 

Dry Compressors. — This type of compressor has a cylinder and piston 
similar to those of a steam engine, with suitable outlet and inlet valves at the 
cylinder ends. The temperature of the air is kept within reasonable limits by 
the constant flow of cold water through the water jacket of the cylinder from 
the bottom upward. It is, however, doubtful if this process of cooling, even 
under the most favorable conditions, does more than keep the cylinder from 
becoming excessively heated and so imparting heat to the incoming air. A more 
thorough method of cooling is obtained by injecting a fine spray of cold water 
into the cylinder near the outlet valves. To this the objection has been strongly 
urged that the presence of water with its non-lubricating properties causes an 
undue wear and tear in the cylinder and loss in power. 

3. — CAUSES OF LOW EFFICIENCY IN AIR COMPRESSORS. 

These causes briefly stated are the heating of the air during compression, 
mechanical defects in the inlet and outlet valves, and leakage past the piston. 
It has been already shown that air when subjected to compression is heated, 
and that as the volume is thereby increased, much power is uselessly expended 
in dealing with the heated air. The most efficient compressor therefore, in this 
regard, must be the one presenting the best cooling arrangement for the air as it 
is being compressed. That form of compressor in which the piston is represented 
by the falling water supplying the power, such as Sommeiller's, permits of a very 
thorough cooling, as the water piston is renewed each stroke, and the cylinder is 
kept perfectly cool. 

But in the second form of wet compressor, such as Dubois' of Mariehaye 
Colliery, Belgium, in which the water, only slightly renewed per stroke, becomes 
considerably heated, the cooling is not more perfectly effected than in the dry com- 
pressor. As the pressure to which the air is raised becomes greater, the losses 
from this source become serious, and as the efficiency of the motors increases 
with the pressure, and the size of the conduits can be correspondingly small it is 
desirable, particularly in large installations, to use high-pressure air. The most 
satisfactory results in this direction have been obtained by stage compression— 
that is, by pressing the air to a certain pressure in one cylinder and further com- 
pressing it in a second, and, if desired, in a third, or even a fourth. By this 
system the air is cooled between each stage, and the losses from this source are 
minimized. For low pressures it is doubtful if any practical economy would re- 
sult from stage compression, but it is now fully demonstrated that for pressure 
above 60 lbs. the advantages of stage compression are very marked. To diminish 
losses caused by resistance to the passage of the air through the inlet and outlet 
valves many devices have been resorted to. In the ordinary valves held to their 
work by springs the valves rattle or chatter if the springs are weak. On the 
other hand, if the springs arc made very strong, a resistance to the passage of 
the air is set up, resulting in a loss of power which in some cases becomes 
serious. To obviate this defect the valves are occasionally devised to open me- 
chanically. In a short paper such as this it is impossible to enter into the details 



TRANSMISSION. 287 

of the various valves used. It is not uncommon to hear much stress laid on the 
losses caused by the unavoidable dead space occupied by compressed air at the 
end of each stroke, and it may be pointed out at once that the loss is not in 
power, but solely in the volumetric capacity of the compressor. To diminish 
this inconvenience, the air piston is usually run as close to the cylinder ends as 
practicable, and care is requisite to avoid sailing too close to the wind in this 
direction and damaging the mechanism. The best plan is to arrange trick pas- 
sages or grooves on the inside of the cylinder, for a short distance back from 
each end, to allow the air in the dead space to pass the piston to the end in which 
compression is about to begin. The inside pressure against the suction valves 
is thereby relieved, and compression on the other side of the piston begins at 
once. To prevent knocking, through the sudden relief caused thereby at the 
end of the stroke, a certain amount of cushioning in the steam cylinder is re- 
quired. The low efficiency, due to leakage of the pistons, can only be effectually 
reduced by carefully attending to their condition. Naturally the higher the com- 
pression the greater the leakage; but stage compression greatly lessens this evil. 

4. — AIR CONDUITS. 

Two considerations are of importance in determining the pipes to be em- 
ployed; these are the size of the pipes and the character of the joints. The fric- 
tional loss .in the passage of the air through the pipes increases very rapidly as 
the diameter decreases, as shown by the following example. If a volume af air 
at 60 lbs. pressure, equivalent to 18,000 cubic feet per hour at atmospheric pres- 
sure, be passed through 1,000 ft. of pipes the loss of pressure of air for 2^ in., 
3 in., y/i in. and 4 in. pipes would be 5^ lbs., 2 lbs. and i^ lbs. respectively. 
Leakage at the joints, through the expansion and contraction of the pipes, is a 
fruitful and at times a serious source of loss of power. A receiver of suitable size 
should always be placed alongside the compressor, and where a considerable 
length of pipes is used, it is an advantage to have a receiver as near the motor 
as practicable. 

5. — METHOD OF USING COMPRESSED AIR. 

When air is compressed it is heated, and when it expands it is cooled. 
The latter fact gives rise to the inconvenience so frequently met with in air 
motors, of ice being formed in the ports, through the freezing of the moisture 
in the air. Where the air is admitted to the motor practitally during the whole 
stroke there is little danger of ice being formed, but there is a terrific waste of 
power, for it is as important for economy to use air expansively as it is to use 
steam expansively. While a little moisture in air used expansively results in the 
formation of ice in the ports, it may be pointed out that aqueous vapor has a 
specific heat nearly double that of air, and consequently cools less rapidly under 
expansion than dry air, and the tendency of an excess of moisture is to reduce 
the cooling. The specific heat of water being still greater, a spray of water may 
be effectively used in the motor cylinder to prevent cooling to the frcc/ing point. 
The writer was familiar many years ago with an instance where, in the case of 
large haulage engines placed underground, the inconvenience caused by freezing 
was so serious that compressed air was abandoned, and steam, though incon- 



288 TRANSMISSION. 

venient, was substituted. Reheating the air is, however, the most effective 
method of allowing air to be used expansively, without the formation of ice in 
the ports, and this can best be done by passing the air near the motor, through 
a coil of pipes heated by a small furnace ; and a further elaboration, permitting 
the highest degree of expansion, is effected by introducing a small quantity of 
water into the heater, where it is converted into steam. A move in the latter 
direction was made years ago by the use of a jet of steam in the air pipe, near 
the motor. In practice it is found that reheating the air not only prevents freez- 
ing, but results in a very great economy in the use of compressed air at a small 
cost both for plant and fuel. 

6. — DANGERS ATTENDING ITS USE. 

These are so slight as to be scarcely worth considering but their existence 
is worthy of passing notice. A few cases are known where an explosion, more 
or less marked, has occurred in the receiver placed near the compressor. In 
these instances combustion has been set up apparently in the carbonaceous mat- 
ter, deposited from the lubricants used in the compressor. The readiness with 
which a piece of old oily waste takes fire at comparatively low temperature is 
well known, and it is possible that a similar action may take place in the 
deposited carbon, if subjected accidentally to abnormal heating by a failure in 
the cooling apparatus of the compressor. 

The use of compressed air seems at first sight an extremely simple one, 
and consequently the principles surrounding its use are seldom inquired into. 
The results obtained from it are, in consequence, at times appallingly poor, and 
its reputation as a means of transmitting power suffer proportionately. In the 
worst forms of machines lo per cent, only of the power expended may be ob- 
tained, and the writer has a distinct recollection of the care with which his 
Belgian professor demonstrated the impossibility of obtaining more than 23 P^r 
cent, of useful effect from compressed air. But to quote from Professor Good- 
man : "In the best cases, without reheating about 55 per cent, and with reheating 
75 per cent, of the total power is given out by the motor." The extensive use 
made of compressed air in metalliferous mines, particularly for rock drills, 
should naturally induce an intelligent interest in its use in Australia, and a dis- 
crimination in the proper and improper methods of employing it. 



COMPRESSED AIR TRANSMISSION PLANT AT THE NORTH STAR 

MINE. 

The paper read by Mr. Arthur De Wint Foote, C. E., at the meeting of the 
American Society of Civil Engineers, recently convened in San Francisco, 
elicited much interest and no small amount of -discussion. 

The paper referred to makes a very elaborate and exhaustive report upon 
the operation of the compressed air transmission plant of the North Star Mine 
in Grass Valley, Cal.; a brief description of which', compiled from this report, 
we here present. 



TR.\NSMISSION. 289 

The power station consists of a Pelton Wheel, 18 ft. 6 in. in diameter, 
attached direct to the shaft of a Rix Duplex Air Compressor, compound tandem 
type. The initial cylinders are 18 inches, and the second cylinders 10 inches 
diameter, with a 24-inch stroke. 

The wheel is built up of angle iron plates riveted together to break joints, 
and is held concentric with the shaft, with 12 pairs of radial spokes of i^-inch 
rod iron secured by nuts to the cast iron hub. The driving force being applied to 
the rim, is transferred to the hub by four pairs of 2-inch iron rods so arranged 
as to form a truss. 

The wheel weighs 10,500 pounds, and runs at no revolutions under 750 
feet head, developing upwards of 300 h. p. It is made of this large diameter for 
the purpose of giving proper speed to the compressor under the high head in this 
case available. The water is applied to the wheel through a variable nozzle con- 
trolled by a hydraulic regulator which maintains a uniform speed on the wheel 
with a variation from full load down to 25 per cent, of same, making its opera- 
tion absolutely automatic, as well as economizing the water supply, no more being 
used at any time than required for the work. 

The construction of the wheel, as will be seen, forms an ingenious mechan- 
ical combination, altogether novel and without precedent, affording an ample 
factor of safety with a very high peripheral velocity. The water supply is brought 
to the wheel through 25^ miles of 22-inch riveted pipe, affording sufficient capa- 
city to develop 800 h. p. A 6-inch lap-weld pipe conveys the air at a pressure of 
90 pounds from the power house to the company's shaft, 800 feet distant and 125 
feet elevation. This is at present running a ico h. p. pneumatic hoisting engine 
and a 75 H. p. compound pump, beside other pumps, drills, forges, etc. 

The report above referred to shows that repeated tests on this wheel, made 
by the most approved methods and checked up very closely, give the remarkable 
efficiency of 93 per cent, at full load ; also an average efficiency of something over 
90 per cent, for Y^, 3^, ^ and full loads. The suggestion has been made that the 
extraordinary efficiency here shown is accounted for in part by the unusual di- 
mensions of the wheel. This, however, was shown to be incorrect, as equally high 
efficiencies have been obtained on Pelton wheels of much less than one-third this 
diameter. 

The efficiency of compression and transmission from water wheel to 
motors, not including cost of reheating, is given as 79 per cent., making a most 
favorable showing for the plant as a whole, under the conditions installed. The 
application here described is also of interest as showing the remarkable flexibility 
of the Pelton system and facility of adaptation to all varying conditions. 



ECONOMY OF COMPRESSED AIR POWER TRANSMISSION. 



BY WM. 0. WEBBER. 



The recent great interest in compressed air for power transmsision sug- 
gests that a few figures on the possibilities of this method of storing and con- 
verting energy might be pertinent. It has recently been found possible to com- 
press air directly by falling water without the necessity of using water wheels, 



290 TRANSMISSION. 

with the consequent loss in friction of from 15 to 20 per cent., and also the loss 
in transforming the rotary motion by means of displacement compressors, with 
the further consequent loss due to the raising of the temperature of the air com- 
pressed and the condensation of the water vapor from the air. In fact, this last 
feature has been one of the chief obstacles to the use of compressed air. 

It is a well-known fact that water vapor contained in air may be condensed 
by falling temperature and also by an increase in pressure. The atmosphere holds 
varying amounts of water vapor, depending almost wholly upon its temperature. 
At 75 deg. Fahr. i cu. ft. of air can hold 10 grains of water vapor. Under aver- 
age conditions it would hold 7 or 8 grains. Suppose i cu. ft. of air to be com- 
pressed from atmospheric pressure — ^that is, 14.7 lbs. per square inch — ^to 100 lbs. 
gauge pressure. The volume of the air and vapor will be reduced to about one- 
eighth. The effect of the rise of temperature upon the vapor contained in the air 
when no cooling device is used, exceeds the effect of the increase in pressure, and 
no condensation of the contained vapor takes place during compression ; but the 
air must, during transmission, lose heat and return to about the same tempera- 
ture as before compression, consequently from three-fourths to seven-eights of 
the vapor will be condensed, because i cu. ft. at the higher temperature holds 
eight times as much vapor as i cu. ft. of the atmosphere. Hence the water will 
constantly collect in the air mains, and in cold weather will freeze and obstruct 
the passage of the air. 

In short transmission the air may not suffer a great fall in temperature, 
and may carry the larger portion of the vapor with it; but the sudden and con- 
siderable fall in temperature caused by the air expanding against the resistance 
of the pistons is sufficient, not only to condense, but also to freeze the moisture 
in the cylinder and exhaust ports of the engine. This is a continual source of 
trouble in many instances where air has been compressed by cylinder com- 
pressors. An attempt is made, with only partial success, to overcome this dif- 
ficulty by having a large receiver where the air may cool down and deposit its 
moisture, after compression and before it is used. The above device, however, 
will not in most cases free the air of moisture sufficiently to insure absence of 
freezing in engines when there is no reheating. 

In compressing air directly by falling water, the bubble of air while pass- 
ing down the compressor pipe is kept cool by a body of water surrounding it. 
The time of compression is comparatively slight, being from fifteen to twenty sec- 
onds. The bubble of air is compressed at a constant terminal pressure, being 
that due to the depth of the water, and the excess of water caused by the gradual 
increase of pressure is deposited on the walls of the bubble. A test made of air 
hydraulically compressed to 52 lbs. gauge pressure showed that it only contained 
one-fifth of the vapor usually contained in atmospheric air during fine weather, 
or 14 per cent, of saturation. 

If air at 35 deg. Fahr. is heated under a constant pressure, its volume will 
be increased one four hundred and ninety-fifth for each degree over 35 degs. 
Air at a temperature of 70 deg. Fahr., if heated to a temperature of 340 deg. 
Fahr., will increase in volume 50.94 per cent. If, when so heated, this air is thor- 
oughly saturated with moisture by being passed through a tank of water at about 
the same temperature, each 50 cu. ft. of free air is found to absorb about i lb. 



TRANSMISSION. 291 

of water in the form of steam; hence the steam adds more than 50 per cent, to 
the volume of air. Thus the expansion by saturating with steam and reheating 
increases the volume more than 100 per cent., or, in other words, doubles the 
amount of work that any original quantity of compressed air will do. The cost 
of the reheating is trifling. 

The coal required to reheat and secure double efficiency is less than one- 
eighth of the coal required to do the same amount of compressing with a cylinder 
compressor, or, reconverting this back into efficiency of work done, it is safe to 
a'ay that the cost of reheating would represent 8 per cent, of efficiency. 

To note what this all means, taking the figures obtained from the tests 
made in Paris in compressed air transmission, the results to be obtained by com- 
pressed air are as follows : 

PERCENTAGES OF EFFICIENCY. 

Air compressor 75 

Pipe line 98 

Reheating and saturating which equals the addition of 100 

Then the use of air motors which will give 8i 

Would give a total of 119 

But as the cost of this reheating equals a net result of 87 per cent., the 
actual net economy is about 103 per cent. This economy of course is limited to 
conditions in which the cost of pipe for distributing the compressed air and the 
reheating apparatus would not eat up all the profit. It would then be preferable 
to compress the air at 75 per cent, efficiency, reheating and moistening it, which 
*vould add 100 per cent., convert this air directly into rotary motion by the air 
motors giving 78 per cent., then through step-up transformers at 96 per cent., wire 
line at 95 per cent, and step-down transformers at 96 per cent., giving 96 per cent, 
of the original power, or, taking the loss of heating into effect, 90 per cent, of the 
original power instead of a net efficiency of about 60 per cent, to 65 per cent, if 
the same amount of water was used in water wheels and converted directly into 
electricity and transmitted. 

I have gone into some pretty careful figures recently regarding the cost of 
development under these different conditions, assuming the quantity of water to 
equal 5,000 h. p., to be transmitted four miles, and have figured out that by 
water wheels and electrical transmission we would obtain a net of 3,000 h. p. at the 
end of the line, at a cost of installation of $46 per h. p. The cost of compressing 
the air, reheating it, and then converting it into electricity and sending it over a 
wire conies to about forty-three dollars ($43) per h. p., and I believe it would 
be possible, with a water power situated not more than two miles from the edge 
of a town, to transmit the compressed air to that point by pipe, and then convert 
and distribute the power and light by electricity for forty dollars ($40) per h. p. 

In a recent publication I saw a reference made to the utilization of the 
water at the Iron Gates of the Danube, and it struck me at once that it would 
be a feasible proposition to use this power in the form of compressed air for the 
purpose of propelling the boats up the river and through the canals which are 
to be constructed, thus making the power of the falling water passing down 



292 TRANSMISSION. 

through that famous gorge, do the work of propelling the boats up against its own 
current. This, of course, seems somewhat impractical, but upon careful thought, 
I do not see that it is any more so than water pumping itself up hill, as it cer- 
tainly does in a hydraulic ram. 



THE FLOW OF COMPRESSED AIR IN PIPES. 



BY WILLIAM COX. 



The volume of a fluid discharged from a pipe is very easily ascertained by 
means of the formula 

V X 0.7854 d" X 12 X 60 

D = 

1728 

= V X d^ X 0.32725 ( I ) , 

Where D = discharge in cu. ft. per minute, 

V = mean velocity of flow in feet per second, 
d = internal diameter of the pipe in inches. 
With this formula it, however, generally happens that the velocity v is an 
unknown quantity, as the application of indicating instruments is either difficult 
or altogether impossible in existing pipe installations and out of the question in 
the case of new ones when being designed. Recourse must, therefore, be had to 
some other means to ascertain the actual or required rate of flow of the fluid, and 
to this end scientists and engineers have long directed their best energies. 

It is well known that if it were possible to eliminate all kinds of friction 
and other opposing forces, the velocity of flow of water in a pipe would be the 
same as the velocity acquired by a heavy body which has fallen from a height 
equal to the head of water; that is — 



V = 1/ 2gh = S.02 1/ h (2) 

Where v = final velocity in feet per second of the falling body, 

h = head of water, or space fallen through in feet, 

g = the force of gravity = 32.16. 

In the case of fluids flowing through pipes there are, however, various op- 
posing forces and other influencing circumstances, all of which (as they produce 
friction and affect the velocity or rate of flow, and materially diminish the prac- 
tical value of the head), must be taken into consideration. These may be briefly 
classified as follows : 

1. Friction induced by the fluid entering the pipe. This is comparatively 
small so that it need not be taken into account when considering pipes of a 
length equal to 400 or 500 times their diameter, or what are termed long pipes. 

2. The friction caused by the flow of the fluid in the pipe. This is propor- 
tional to the length of the pipe, when the velocity is the same throughout, also to 
the circumferential area of the inner surface of the pipe. It also varies in intensity 
in proportion to the internal condition of the pipe, and is likewise affected by the 



TRANSMISSION. 293 

density of the fluid. This latter cause of velocity is not apparent in the case of 
water, as being an almost incompressible body, its density is not appreciably af- 
fected by changes of pressure, but in the case of elastic fluids such as air, steam 
or gas, this factor is an important one and must always be taken into account. 

A general formula applicable to the flow of water in clean pipes, deduced 
from these considerations, is 



/d X h (3) 

V = c / 

Where v = velocity of flow in feet per second, 
d = diameter of the pipe in inches, 
h = total head of water in feet, 
1 = length of pipe in feet, 

c = a variable co-efficient to be determined by experiment. 
It was found by D'Arcy and some others that the co-eflicient c was not a 
constant one to be used for all sizes of pipes. D'Arcy devoted much time to the 
working out of a series of co-efficients applicable to various diameters of pipes, 
and this formula so modified has been generally accepted as giving approximately 
correct results. 

It has also been affirmed by some engineers of authority that this formula 
is also applicable to the flow of an elastic fluid in a pipe by the insertion of a 
term denoting the density of the fluid. Replacing in Eq. (3) the term head of 
water by its equivalent pressure in pounds per square inch, we then obtain 



/d X (pi— P2) (4) 

V = c / 

\/ Wi X 1 

Where pi = initial gauge pressure in lbs. per square inch, 
P2= final gauge pressure in lbs. per square inch, 
p^ — p^=z difference of pressures, or pressure required to overcome friction 
and produce the velocity of flow, equivalent to the loss of head, 
Wi = density or weight in lbs. per cu. ft. of the fluid at the initial pressure 

Pi. 
The other letters represent the same terms as in previous equations. 
If the value of v as given in Eq. (4) is inserted in Eq. (i), we obtain 



/d^x (pi— P2) (5) 

|/ Wi x 1 

which gives the discharge of compressed air in cu. ft. per minute from a pipe of 
any diameter and length, with any initial and final pressures, the volume of dis- 
charge thus obtained being under the terminal pressure pz. To apply this formula 
to practical use, D'Arcy's co-efficients for different actual diameters of pipes, modi- 
fied to suit the conditions of elastic fluids, are here given. 

TABLE 27. 
Diam. Co-efflc't. Diam. Co-efflc't. 

1 inch 45.3 4 inches 57.8 

2 inches 52.7 5 " 58.4 

3 " 56.1 6 " 59-5 



294 



TRANSMISSION. 



Diam. 



Co-efflc't. 



Diam. 



Co-effic't. 



7 inches 60.1 

8 " 60.7 

9 " 61.2 

10 " 61.8 



12 inches 62.1 

14 " 62.3 

16 " 62.6 



To further simplify calculation, the following table gives the values of 
c y^d^, and if we call this term x, we then obtain the simpler formula 

(6). 



-P2. 
xl 



D = x/ 

V __ 

The values of x = C|/d^ in this table are slightly modified so as to make them 
conform to a perfect curve. 

TABLE 28. 
Diam'r C. x = c^^^ 

45-3 45.3 

52.5 297 

56.2 876 

58.0 1856 

.....59-0 3298 

59-8 5273 

60.3 7817 

60.7 ^ 10988 

61.2 14872 

61.6 19480 

61.8 24800 

62.0 30926 

62.2 37898 

62.3 45690 

62.5 54462 

62.6 64102 

It must of course be understood in connection with all pipe calculations that 
the diameters referred to are always the actual ones and not the nominal ones, 
otherwise considerable divergences may be obtained between the calculated and the 
real discharges. Thus the actual inside diameter of a i-inch pipe, "Standard" 
dimensions, is 1.048 inches, giving a sectional area of nearly 10 per cent, more 
than the nominal one. The following table gives the nominal and the actual 
diameters and areas of "Standard" steam, gas and water pipes. It is taken from 
"Book of Standards," issued by the National Tube Works Co. : 



I 


inch . . 


2 


inches 


3 


" 


4 


(( 


5 


(I 


6 


" 


7 


" 


8 


" 


9 


" 


ID 


" 


II 

TO 


« 


13 


« 


14 


« 


15 


(t 


16 


" 



TABLE 29. 



Diam 



NOMINAI.. 



Area. 

inch 0.7854 

inches 31416 

" 7.0686 

" 12.5664 

" 19.635 



Diam'r 

1.048 

2.067 

3-067 

4.026 

5045 



Actual. 

Area. 

0.8626 

3356 

7.388 

12.73 

19.99 





Actual. 


Diam'r 


Area. 


6.065 


-28.888 


7.023 


38.738 


7.982 


50.04 


8.937 


62.73 


10.019 


78.839 


11.25 


99.402 


12.00 


113.098 


13-25 


137.887 


14.25 


159.485 


1525 


182.655 



TRANSMISSION. 295 

Nominal. 
Diam. Area. 

6 inches 28.274 

7 " ...-. 38.485 

8 " 50.266 

9 " 63.617 

10 " 78.540 

11 " •... 95.033 

12 " 113.10 

13 " 132.73 

14 " 153.94 

15 " 176.71 

These real diameters should always be taken into account when using the 
formulas, and if not actually inserted in them, the differences existing should be 
allowed for. 

To further facilitate the investigation of this formula, Table 30 is added, 
giving the values of Wj and i/wj in equations (5) and (6) for pressures up to 
100 pounds, calculated from the formula 

wi = 0.0761 (0.068 pi + i) (7) 

where pi = the initial gauge pressure of the air in lbs. per square inch, at the en- 
trance to the pipe. 

TABLE 30. 

Gauge Pressure. y/ i/Wi 

o pounds 0.0761 0.276 

5 " 0.1020 0.319 

10 " 0.1278 0.358 

15 " 0.1537 0.392 

20 " 0,1796 0.424 

25 " 0.2055 0.453 

30 " 0.2313 0.481 

35 " 0.2572 0.507 

40 " 0.2831 0.532 

45 " 0.3090 0.556 

50 " 0.3348 0.578 

55 " 0.3607 0.600 

60 " 0.3866 0.622 

65 " 0.4125 0.642 

70 " 0.4383 0.662 

75 " 0.4642 0.681 

80 " 0.4901 0.700 

85 " 0.5160 0.718 

90 " 0.5418 0.736 

95 " 0.5677 0.753 

100 " 0.5936 0.770 



ti^ 



296 



TRANSMISSION. 



When, as is generally the case, it is required to know the equivalent volume 
of free air corresponding to the volume of compressed air discharged, this latter, 
or D, must be multiplied by the density of the air at terminal pressure as related 
to the density of the atmosphere. We have for this purpose the following formula : 

F = D X W2 (8). 

in which D = volume of compressed air discharged at final pressure, 
F = equivalent volume of free air, 
W2 = density of the discharged air in atmosphere, = (0.068 po) + i, 
P2 = final gauge pressure in lbs, per sq. in. of the discharged air. 

The following table of values of W2 will be found of use in solving such 
problems : 

TABLE 31. 



P2 W2 

o pounds i.oo 



5 

ID 

15 
20 

25 
30 

35 
40 

45 
50 



1-34 
1.68 
2.02 
2.36 
2.70 
304 
3.38 
372 
4.06 
4.40 



P2 W2 

55 pounds. 4.74 

' 5.08 



60 

65 
70 

75 
80 

85 
90 

95 
100 



542 
5.76 
6.10 

6.44 
6.78 
7.12 
7.46 
7.80 



In Compressed Air the application of D'Arcy's formula to the flow of 
compressed air (an elastic fluid) in pipes was shown in detail. In this number 

a copyrighted table of values of a/ P^~P^ is given, which both facilitates and 

' Wj 

simplifies very considerably the use of the formula. Making a separate term of 
the above we obtain the complete formula in this simpler form 



c 1/ d-^ 



\ Wi 



(9) 



in which 

D = volume of compressed air discharged at final pressure in cubic feet per 

minute, 
d = actual diameter of the pipe in inches, 
1 = length of the pipe in feet, 

c =a co-efiicient varying with the diameter of the pipe (see Table 28), 
Pi = initial gauge pressure in pounds per square inch, 
p2 = final gauge pressure in pounds per square inch, 

Wi= density or weight in pounds per cubic foot of the air at the initial 
pressure pi when entering the pipe (see Eq. (7) and Table 30). 



TRANSMISSION. 



297 



Values of c \/d^ for various sizes of pipe are given in Table 28, and values 

of a; P^ P^ for any final pressure p„ from 20 to 100 pounds, and for any loss of 

pressure from i to 10 pounds are given in Table 32, as follows : 

TABLE 32. 



iJoMe <}j( fcUuej a% /^LTzZi. 



.--Cl^ 






Qmi, 



'^^ 






az . 

^ . 

M> . 

:is . 
^^. 
M> . 
3/ . 
JJi , 
33 . 
3/^ . 
JJ- . 
.36 . 
3/ , 
M . 
3f . 
Ao- . 
A/ . 



-/^ jiJL. J^. y^^. d-^. 6^. yM.. /^^. ^M.. y^^. 






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2.133 J./// J. 77^ 4.dff/^ ^./'f^ ^/J-JZ ^S2?/ ^J'/'f^ ^.//>Z 6.3^Z 

2.z{rs J (ry^ j.piy j^.zjr/^ ^y^^z x^Ja^^/^^r\^.^^^^<^ /f^<^ 
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/.'fp^ z.i>3Z 3./f^ 3.^3 j^.^^4 4./^cj^ ^.p/p 3:^;irz s.zJs- s:sYr^ 
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J^ > 
J/ . 

J3 . 

f • 
4/ . 



♦ Copyright 1898 by The Ingereoll-Sergeant Drill Co., New York. Published by permission. 



298 



TRANSMISSION. 



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TRANSMISSION. 299 






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7J . 

?¥• 

7'r. 



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A few practical examples are now given to show the application of the 
formula, and also the use of Table 32. The simplicity by which solutions are ob- 
tained of what would otherwise be very tedious calculations, will be seen to be 
most striking. 

Example i. How many cubic feet of compressed air will be discharged 
from an 8-inch pipe, 10,000 feet long, the initial pressure being 80 pounds, and the 
loss of pressure not to exceed 4 pounds? Also what will be the volume of equiva- 
lent free air ? 






300 TRANSMISSION. 

Here p2 = "]^ lbs. 



V- 



c / cP = 10988 (Table 28 ) 
Pi— P2 _ 



2.856 (Table 32.) 

Wi 



and y I = y locxx) = 100. 

Therefore by Eq. (9) we have 

10988 

D ^2.856 

100 

= 314 cubic feet compressed air per minute at 76 lbs. final pressure. 
Now by Eq. (8) and Table 31 we have 
F =3 D X 6.168 = 314 X 6.168 

= 1936.7 cubic feet equivalent free air. 

Example 2. It is required to transmit through a pipe 7056 feet long, the 
equivalent of 800 cubic feet of free air, the initial pressure being 60 lbs., and the 
loss of pressure not to exceed 5 lbs. What must be the diameter of the pipe? 

Here p. = 55 lbs., 



4 



PiIlP^= 3.596 (Table 32) 

Wi 



and |/ 1 = |/ 7056 = 84. 
Now by transposing Eq. (8) and by Table 31, 
F 800 



D = 



w. 4.74 

= 169 cubic feet compressed air discharged at 55 pounds final pressure. 
Then by transposing Eq. (9) we have 



c ]/ d"^ = D X 1/ 1 -- I pi — Pa (10). 



[69 X 84 



= = 3947 

3.596 

We now see from Table 28 that this value 3947 corresponds to a pipe about 
5>^ inches diameter. A 6-inch pipe should therefore be selected. 

Example 3. It is desired to lay a 9-inch pipe, 10,000 feet long, which shall 
discharge 400 cubic feet of air per minute compressed to 60 lbs. final gauge pres- 
sure. What will be the loss of pressure? Also what must be the initial pressure? 
Here D = 400, 
d=9, 
c i/"cF= 14872 (Table 28.) 
P2 =3 60, 

|/ 1 = 1/ loooo = 100 
whence it is required to find pi — p- and also pi. 



TRANSMISSION. 301 

This problem is the most tedious one which presents itself in connection 
with the flow of compressed air in pipes, seeing that, as has been shown in con- 
nection with Eq, (4) pi and wi, which are unknown quantities, are inter-depend- 
ent, each one having a different value as the value of the other one varies. By the 
usual method we cannot proceed directly but must adopt an indirect or tentative 
method of solution. With Table 32, however, the problem is exceedingly simple. 
Thus, transposing Eq. (9) we have 



V- 



DXy/ 1 (II). 



c i/d^ 
400 X 100 

14872 

= 2.690. 

Now looking at the table along final pressure p^ ^ 60 lbs., we see that 

V- 



Wi 

is equal to 2.242 for a loss of 2 lbs., 
and 2.730 " " " " 3 " 

so that for 2.690 the proportionate loss pi — p^ will be 2.9 lbs., thus making the 
required initial pressure pi to be 60 + 2.9 = 62.9 lbs., or say 63 lbs. 

If it should now be desired to find the equivalent volume of free air neces- 
sary to supply the required volume of compressed air, so as to ascertain what 
should be the capacity of the compressor, we have from Table 31 

Free Air required at Compressor = 400 X 5.08 

= 2032 cubic feet of free air to be com 

pressed to 63 lbs. initial gauge pressure. Dividing this by 5.284 (the relative value 
of wi for pi = 63 lbs., according to Eq. (8) gives 384.5 cubic feet per minute as 
the volume of compressed air required to enter the pipe at 63 lbs. initial gauge 
pressure, and which, owing to the loss of pressure caused by the friction in the 
pipe, expands to 400 cubic feet per minute at 60 lbs. final or exit pressure. 

Of course it must be understood that in these calculations no allowances 
are made for losses other than those caused by friction in the pipe. Should the 
existence of leakage or any other losses be known, such as between the com- 
pressor and the receiver, or the receiver and the entrance to the pipe, bends, etc., 
they must be ascertained and allowed for separately, by the introduction into 
the compressor of a proportionately greater volume of free air. 

A few more examples will be given in the next article, as also some deduc- 
tions which a closer study of the formula brings to our notice. 

Equation (7). 

wi = 0.0761 (0.068 pi + 1.) 
where Wi = density or weight in lbs. per cu. foot of the fluid at the initial pres- 
sure pi. 



302 



TRANSMISSION. 



Equation (8). 
F =: D X W2 
in which D = volume of compressed air discharged at final pressure, p2. 
F = equivalent volume of free air, 

W2 = density of the discharged air in atmospheres, = (0.068 pa) + 
p:; = final gauge pressure in lbs. per sq. in. of the discharged air. 



TABLE 28. 



Diam'r. 

1 inch . . . 

2 inclies. 



c/d5 

45-3 

297 

876 

1856 

3298 

5273 

7817 

10988 

14872 

19480 

24800 

30926 

37898 

45690 

54462 

64102 



TABLE 30. 
Gauge Pressure. Wi 

o pounds 0.0761 

0.1020 

0.1278 

...•: 0.1537 

0.1796 

0.2055 

0.2313 

0.2572 

0.2831 

; 0.3090 

0.3348 

0.3607 

0.3866 

0.4125 

0.4383 

0.4642 

0.4901 

0.5160 



5 
10 

15 
20 

25 
30 
35 
40 

45 
50 
55 
60 

65 
70 

75 
80 

85 



0.276 
0.319 
0.358 
0.392 
0.424 

0.453 
0.481 
0.507 
0.532 
0.556 
0.578 
0.600 
0.622 
0.642 
0.662 
0.681 
0.700 
0.718 



TRANSMISSION. 303 

Gauge Pressure. w^ V^i 

90 pounds 0.5418 0.736 

95 " 0-5677 0.753 

100 " 0.5936 0.770 

TABLE 31. 

P2 W2 P2 w.. 

o pounds 1. 00 55 pounds 4.74 

5 " 1-34 60 " 508 

10 " 1.68 65 " 5.42 

15 " 2.02 70 " 5.76 

20 " 2.36 75 " 6.10 

25 " 2.70 80 " 6.44 

30 " 3-04 85 " 6.78 

35 " 3-38 90 " 712 

40 " 3-72 95 " 746 

45 " 4.06 100 " 7.80 

50 " 440 

Example 4. — It is required to discharge from a 6-inch pipe, 6400 feet long, 
the equivalent of 1166 cu. ft. of free air at a terminal pressure of 60 pounds. 
What must be the initial pressure? 

Here F = 1166, d = 6, c / d^ = 5273, 1 = 6400, pa = 60, w^ = 5. 8. 

Then, by Eq. (8) transposed 

V 1 166 

D = = = 229.5 cu. ft. at 60 lbs. 

Wg 5.08 

By Eq. (11) 



V- 



Pi — P2 _ 229.5 X 80 
I 5273 

= 3482- 
Now running the eye along the line in Table 32 of 60 lbs. terminal pres- 
sure, we find under 5 lbs. loss the value of 



a/- 



-^ = 3 479 



This is therefore the resulting friction pressure, whence the initial pressure must 
be 60 + 5 = 65 lbs. 

Example 5. — Take the same case as Example 4, but limit the loss of pres- 
sure to 2 lbs. How much air will be discharged at 60 lbs. final pressure? 

From Table 32 under 2 lbs. loss, and opposite 60 lbs. final pressure, we 
find 



V- 



w, 
Inserting this in Eq. (5) we obtain 



P, -P. ^2.242 



D = i-7^ X 2 242 
80 

= 147.76 cubic ;feet air at 60 lbs. final pressure. 



304 TRANSMISSION. 

Supposing now that this quantity does not suffice, what diameter of pipe 
will be required to discharge the 229.5 cu. ft. air at 60 lbs. with a loss of 2 lbs. 
only, making the initial pressure = 62 lbs.? 

By Eq. (10) 

2.242 
= 8185. 

From Table 28 the diameter of the pipe would have to be about 7^ inches. 

Example 6. — It is desired to discharge from a 4-inch pipe 150 cu. ft. air at 
a final or exit pressure of 60 lbs. How long can the pipe be so that the loss of 
pressure shall not exceed 5 lbs.? 

Here D =. 150, d = 4, c |/ d^ == 1856, p^ = 65, pg = 60. 
Transposing Eq. (9) and by Table 32, we have 

1 = /^z^ X jhesV (.2) 






= 1851 feet long. 

Example 7. — Supposing that in Example 6, the initial pressure remains at 
65 lbs., and that the pipe is 3706 feet (or twice as long) ; what will be the final 
pressure, the volume of discharge being still 150 cu. ft. of compressed air? 

Here D = 150, d = 4, c i/'d^ = 1856, p^ = 65, 1 = 37L6; 1/ 1 = 60.877. 
Required to find pa. 
By Eq. (11). 



V- 



150 X 60.877 



Wi 1856 

4.92. 



Now by Table •72 we sec that 4.92 is Uie value of ^|Pi El for a final pressure 

^ \ Wi . 

of 55 lbs. with 10 lbs. loss, making the initial pressure 65 lbs. as required. 

It will be noticed that in Example 7 the length of the pipe and the loss of 
pressure are each twice as much as in Example 6, the discharge in each case being 
150 cu. ft. of compressed air. But: — and this is the great point to be noted — 
we have in the former case 150 cu. ft. of air discharged at 60 lbs, final pressure, 
the equivalent volume of free air being 762 cu. ft., whereas in the latter case we 
have 150 cu. ft. of air discharged at 55 lbs. final pressure, whose equivalent 
volume of free air is only 711 cu. ft., or 51 cu. ft. less, being equal to a diminished 
discharge of 6.7 per cent. Hence, zvhen the initial pressure and the volume of 
compressed air discharged from a pipe remain constant, the loss of pressure will 
he proportionate to the length of the pipe. 

For further exemplification of this most important truth, which has been 
so often misstated, see Table 36 following, and also deductions therefrom. 

A formula is like a theorem in Ibgic. If no important truths can be de- 
duced from it, it is of doubtful value. It may therefore in the present case be 



TRANSMISSION. 



305 



;ful to see what this formula teaches regarding the flow of compressed air in 
)es. It will also certainly be interesting to know from those who have had 
practical experience in the matter, if these deductions have had their fulfilment in 
the case of existing installations. 

It seems to the writer that the best method of examining the formula with 
this object in view will be by means of short tables, designed to show the changes 
wrought, in certain of its factors by slightly varying conditions of the other 
factors, and then deducing from each table the truths thus exposed to view. 

In Tables 33, 34 and 35 following, it is assumed that we are dealing with a 
6-inch pipe, 10,000 feet long, thus* giving the value of 



ci/d' 



5273 



/ 1 



^52.73 



TABLE 33. 

Take pi = 60 lbs. gauge, constant, and pi — p2 as increasingly variable. 





Pi— P2 




P3 


Discharge 
Comp. Air. 


Wg 




Pi 


A wi 


Equivalent 
Free Air. 


lbs. 

60 
60 
60 
60 
60 


lbs. 

2 

3 

4 

. 5 


1.608 
2.273 
2.785 
3.216 
3-596 


lbs. 

It 
I 

55 


84.8 
1 19.8 
146.8 
169.6 
189.6 


5.012 

4-944 
4.876 
4.808 
4.740 


425.0 

592-3 
715.8 

815-4 
898-7 



It will be noted here that the initial pressure remains constant at 60 lbs., 
so that the density of the entering air will be likewise constant. The discharge 
of compressed air will be seen to increase with each increase of loss of pressure, 
but in a decreasing ratio, that is, as the square root of the loss of pressure. Thus, 
with a loss of 4 lbs. the discharge is only twice as great as with a loss of one 
pound. It will also be seen that the discharge of equivalent free air increases with 
the increasing loss of pressure, but in a still greater decreasing ratio than that of 
the compressed air discharge, seeing that the ordinary values of W2 are used 
(See Eq. 8) and not their square roots. 

It is also evident that although the initial pressure is maintained at 60 lbs., 
and the loss of pressure increases from one to five pounds, the cost of running 
the compressor zvith the higher loss will he greater, as the increased loss must be 
counterbalanced by the intake of a greater volume of equivalent free air, in order 
that the initial pressure may be maintained at 60 lbs. This condition also applies 
more or less to Tables 34 and 35. 



3o6 



TRANSMISSION. 



TABLE 34. 

Take pi — p2 = 5 lbs. gauge, constant, and pi and p- as uniformly variable. 





Pi— Pa 




Ps 


Discharge 
Conip. Air. 


W2 




Pi 


1 Pi— P2 


Equivalent 
Free Air. 


lbs. 


lbs. 




lbs. 








65 
66 




3479 
3458 


60 
61 


183.4 
182.3 


5.080 
5.148 


931-7 
938.5 


67 
68 
69 
70 




3437 
34^7 
3.397 
3-376 


62 

63 
64 
65 


181.2 
180.2 
1 79. 1 
178.0 


5.216 
5.284 
5-352 
5.420 


945-1 
952.2 

958.5 
964.8 



This table shows that although the initial and final pressures correspond- 
ingly increase, the loss of pressure remaining constant, the volume of compressed 
air discharged decreases in a uniformly decreasing ratio, that is, inversely as the 
square root of the density of the air at its initial pressure. On the other hand the 
volume of equivalent free air entering and being discharged from the pipe 
increases continually, but in a decreasing ratio. 

TABLE 35. 

Take p^ = 60 lbs. gauge, constant, and pi and pi — p- as corresponding 
variable. 











Discharge 








1 Pi— Pa 


Equivalent 


Pi 


Pi P2 


\ Wi 


Pa 


Conip. Air. 


Wo 


Free Air. 


lbs. 


lbs. 




lbs. 








61 


I 


1-597 


60 


84.2 


5.08 


424.5 


62 


2 


2.242 


60 


118.2 


5.08 


600.4 


63 


3 


2.730 


60 


143-9 


5.08 


731.0 


64 


4 


3-132 


60 


165.I 


5.08 


838.7 


65 


5 


3-479 


60 


183.4 


5.08 


931.7 



In this table the initial pressure and the loss of pressure increase uniformly, 
while the final pressure remains constant. It will be seen that the volume of com- 
pressed air discharged increases with the increase of the initial pressure and the 
loss of pressure but in a decreasing ratio, that is, as the square root of the loss 
ot pressure divided by the square root of the initial density. The discharge of 
c(iuivalent free air increases exactly in the same ratio as the discharge of com- 
pressed air, seeing that the value of w- is constant throughout, being dependent 
upon the final pressure p-, which is also constant. 



TRANSMISSION. 



307 



TABLE 36. 

Take a 4-inch pipe 1853 to 37°^ feet long, whence c ;/ d* = 1856. As- 
sume pi = 65 lbs. gauge, constant, and D = 150 cubic feet constant. 





Discharge 
Comp. Air. 


1 




Pi— P3 


P2 


Wa 




Pi 


\ Wi 


Equivalent 
Free Air. 


lbs. 








lbs. 


lbs. 






65 


150 


1853 


3-479 


5 


60 


5.080 


762 


65 


150 


2224 


3.811 


6 


5? 


5.012 


752 


65 


150 


2594 


4. 1 17 


7 


5« 


4.944 


742 


6S 


150 


2965 


4.400 


8 


57 


4.876 


731 


65 


150 


3335 


4.668 


9 


56 


4.808 


721 


65 


150 


3706 


4.920 


10 


55 


4.740 


71L 



Here the discharge of compressed air is constant throughout, and the loss 
of pressure is exactly proportionate to the length of the pipe. As the final 
pressure, and consequently W2, diminish with the length of the pipe, the volume 
of equivalent free air discharged must diminish in the same ratio as W2, as also 
obviously the equivalent volume of free air entering the pipe. If on the other 
hand the volume of equivalent free air entering the pipe at a uniform initial pres- 
sure were constant, it is clear that the loss of pressure would be greater propor- 
tionately than the increase in the length of pipe. 

TABLE Z7- 





Comp. Air 


Equivalent 


I 


Pl-P2 




Discharge 


Pl 


the Pipe. 


Free Air. 




Ps 


Comp. Air. 


lbs.' 


c. ft. 


c. ft. 


feet. 


lbs. 


lbs. 


c. ft. 


6S 


140 


762 


1853 


5 


60 


150 


("> 


140 


762 


2162 


6 


59 


152.1 


("i 


140 


762 


2460 


7 


5« 


154.2 


65 


140 


762 


2730 


8 


57 


156.3 


65 


140 


762 


2988 


9 


56 


158.5 


65 


140 


762 


3226 


10 


55 


160.7 



In this table the initial pressure and the volume of compressed and equiva- 
lent free air entering the pipe are all constant, but the loss of pressure and the 
length of pipe increase, although not correspondingly. Thus, for increasing 
losses of one pound, the length of pipe increase as follows : 

Prop'te 
length. 

1853 feet 

2224 •' 
2594 " 



3s of 5 lbs. 
" 6 - 


Length 
of pipe. 

1853 feet 

2162 " 


" 7 " 


2460 " 


" 8 " 
" 9 " 
" 10 " 


2730 " 
2988 " 
3226 " 



Difference. 



2965 

3335 
3706 



62 feet. 

134 " 
235 - 

347 " 
480 " 



3o8 



TRANSMISSION. 



whence it is clear that when referring to the flow of free air (equivalent) in 
pipes, the loss of pressure isnotproportionate to the length of the pipe, the volume 
of air entering the pipe being constant, as also the initial pressure. 

TABLE 38. 

Particulars of pipe, pressure, discharge, etc., the same as for Table 34. 

D 

Area of pipe == 28.27 square inches, which gives for a 6 inch pipe v = ■ 

11.78 



^ 


Comp. Air 


Veloc- 




Comp. Air 


Veloc- 


Equivalent 


Veloc- 


Pi 


Entering. 


ity. 


P8 


Discharged. 


ity. 


Free Air. 


ity. 


lbs. 






lbs. 










60 


83.66 


7.10 


59 


84.8 


7.20 


425.0 


36.08 


60 


116.60 


9.90 


S8 


119.8 


10.17 


592.3 


50.28 


60 


140.90 


11.96 


57 


146.8 


12.46 


715.8 


60.76 


60 


160.50 


13.62 


S6 


169.6 


14.40 


815.4 


69.22 


60 


176.90 


15.01 


55 


189.6 


16.09 


898.7 


76.29 



From the above it may be noticed that two different velocities have to be 
taken into account. Of these, the velocity of equivalent free air is constant 
throughout the length of the pipe when the initial pressure and the loss of pres- 
sure are maintained at the same point. On the other hand the velocity of the com- 
pressed air is continually varying, being the lowest at entry, and increasing by 
degrees as it flows along to the point of discharge. The formula clearly explains 
the reason of this, seeing that it shows : 

I St. As the compressed air flows through the pipe, friction takes place, 
producing an increasing loss of pressure as the compressed air advances. 

2nd. By reason of this loss of pressure, the pressure to which the air is 
compressed decreases as it flows along. 

3rd. Diminished pressure involves diminished density of the compressed 
air, hence, 

4th. The original volume of compressed air entering the pipe becomes 
continually greater, and as the entry pressure remains constant, this greater 
volume must pass any given point in the pipe in the same time as the original 
smaller volume, whence 

5th. To accomplish this, the rate of speed or velocity of flow must con- 
stantly increase to the end of the pipe. 

Other interesting deductions from this formula could have been made, and 
will suggest themselves. What has been set forth in these articles will, it seems 
tc the writer, show that the formula is applicable to the flow of elastic fluids, such 
as air and steam, in pipes ; that it is logical, and that with the help of Table VI. 
it enables the solution of any practical problem to be quickly and very easily 
obtained. 



f^- 



TRANSMISSION. 309 



Further experience may of course go to show that D'Arcy's co-efficients 
require somewhat modifying, but it should be remembered that no two series of 
experiments can be expected to be undertaken under precisely similar conditions, 
so that slightly varying results must be looked for, but they will not for this rea- 
son affect the reliability of the formula. 



A MUNICIPAL POWER PLANT. 

The following paper on the "Transmission of Power by Compressed Air" 
was recently presented by Richard Hirsch, before the Engineers' Society of 
Western Pennsylvania, Pittsburg, Pa. 

In papers presented to this Society at different times, various methods of 
transmitting power in the city of Pittsburg have been advocated. Up to the 
present time, however, the only agent which has been utilized for this purpose 
is electricity, unless we mention our city water supply, which has been used for 
hydraulic elevators, and in a few instances for motors operating light machinery. 

It has been unfortunate for the reputation of compressed air that so little 
attention has been given to its development as an efficient transmitter of power. 
In most applications its peculiar advantages, such as safety, non-condensation 
during transmission, and unobjectionable exhaust, have been features of first con- 
sideration. Little attention was given to economical operation, inefficient com- 
pressors and wasteful motors being used. Compressed air has many advantages 
which entitle it to a more general recognition as an efficient means of transmitting 
and distributing power in cities. 

In the use of steam, the loss by condensation in the pipe lines, the necessity 
for expensive pipe coverings and expansion joints, and the objectionable exhaust, 
either as steam or hot water, are disadvantages not met with in the use of com- 
pressed air. The high cost of hydraulic power, and the limited possible applica- 
tions of the same, place it in an unfavorable light, when brought into competition 
with pneumatic transmission. The ease with which electric wires can be strung 
on poles, over housetops, and through buildings, and the low cost of such work, 
have been great factors in the rapid increase in the use of electrical machinery — 
much more so, in fact, than the cost of electric power. But vigorous protest 
should be made against the disfiguring of house fronts and interiors by the 
promiscuous array of wires, insulators and transformers. The conversion of 
our streets into veritable forests of unsightly poles, carrying net-works of highly 
charged and uncovered wires, should not be tolerated. When electric conductors 
are laid underground, and interior wiring concealed in the walls and floors of 
buildings and securely insulated, the cost of such work equals, if not exceeds, the 
cost of piping required for transmitting power by other agencies. 

Compressed air is used at pressures varying from that of a more or less 
perfect vacuum up to 5,000 lbs. per square inch. There is a power transmission 
system in Paris where motors are operated by the pressure of the atmosphere 
and exhaust into mains in the streets, in which a more or less perfect vacuum 
is maintained by air pumps situated at a central station. Pressures of from 60 



3IO TRANSMISSION. 

lbs. per square inch to 90 lbs. per square inch are used for ordinary power pur- 
poses; from 400 lbs. per square inch to 800 lbs. per square inch for pneumatic 
locomotives; 2,000 lbs. per sq. inch for street cars, and from 1,000 lbs. per sq. 
inch to 5,000 lbs. per sq. inch for pneumatic dynamite guns and other purposes 
on war vessels. 

The gratifying results obtained in the use of compressed air for operating 
locomotives and shop machinerj^, and the high efficiency that could be obtained 
in a properly designed plant for the general transmission of power, lead the 
author of this paper to believe that such a plant could be successfully operated 
in the city of Pittsburg, considered both from an engineering and business point 
of view. The following is a description of a proposed plant capable of trans- 
mitting 1,100 indicated horse-power, developed in the motors where used, with 
the cost of building and operating the same. 

In a fire-proof building situated on the banks of one of our rivers, and as 
near the business portion of the city as possible, will be installed the necessary 
boilers and air compressors. Water for feeding boilers and cooling purposes will 
be pumped from the river, thereby saving water tax. Coal will be received by 
rail or boat, and handled by machinery. Ashes will also be handled by ma- 
chinery, and loaded into boats or cars as required. Boilers will be of the water 
tube type, fitted with mechanical stokers, and capable of developing 2,000 indi- 
cated horse-power in the steam cylinders of the compressors. There will be two 
air compressors, with triple expansion condensing engines of the Corliss type, 
having steam cylinders 20'', 34" and 50" diameter, by 42" stroke. The air cylin- 
ders will be compound, two for low pressure, each 26" diameter, and one for high 
pressure, 30" diameter; all 42" stroke. The air will be taken at atmospheric 
pressure through a cooling apparatus and specially adapted Corliss valves into 
the two low pressure cylinders, and discharged through an inter-cooler into the 
one high pressure cylinder; the air will there be compressed to 100 lbs. per 
square inch, and delivered through a cooler into the pipe line. Each compressor 
will be capable of delivering about 6,000 cu. ft. of free air per minute, com- 
pressed to 100 lbs. per square inch gauge pressure. The compressor will be 
fitted with automatic valves which will reduce their speed when the pressure in 
the pipe line runs up to a little more than 100 lbs. per square inch and speed them 
up again when the pressure falls. It might, however, be advisable to subdivide 
the compressing machinery into three or more units to facilitate repairing and 
lessen the liability of seriously crippling the plant in case of accident or break- 
down. There is no necessity for large storage tanks or reservoirs, as the air 
mains provide sufficient capacity to permit the air to be pumped directly into 
them. Moisture will be withdrawn from the mains by suitably arranged traps 
and delivered into the sewers. These traps need be but comparatively small 
affairs, connected to the air mains by pipes of small diameter and enclosed in 
the street boxes with the shut-off valves. For the reason that watery or other 
vapors can not be compressed to a density greater than that due to their tem- 
perature, the watery vapor in the air would condense soon after compression, and 
most of it would be drawn off near the power house. 

The main pipe line from the power house will consist of 12" wrought 
iron pipe coupled together by bolted flanges. It will extend to where the next 



TRANSMISSION. 311 

work of street distributing mains begins, and will there be reduced in size as the 
carrying capacity and frictional resistance of each branch of pipe permits. The 
street distributing mains will consist of 6" and 8" wrought iron pipe coupled 
together by threaded sockets. No expansion joints will be required, as the mains 
being laid below the frost line, and the air being cooled after compression in the 
power house, there will be no more variation in the temperature of the air mains 
than there is in water or gas mains, neither of which are provided with ex- 
pansion joints. The expansion joints on the underground steam lines of th^ New 
York Steam Heating Co. are quite elaborate and very expensive affairs, and are 
placed at close intervals. In connection with pneumatic locomotives, wrought 
iron mains with screwed sockets and without expansion joints are used, carrying 
pressures of from 400 lbs. per square inch to 700 lbs. per square inch. The satis- 
factory results obtained in the use of these lines furnish a precedent for advocat- 
ing street distributing mains of practically the same description, although various 
other kinds of joints have been used in Paris and elsewhere for this purpose. 

In the Paris system, steel mains 20 inches in diameter are used, having 
perfectly plain ends and connected together by the so-called Normandy joint, 
which is described in Unwin's Development and Transmission of Power. 

In estimating the cost of construction it has been assumed that the power 
station could be located within 8,000 feet of Eleventh or Grant streets, and allow- 
ance has been made for that length of 12 inch main. Provision has been made 
for laying pipes on all the principal streets of Pittsburg situated between the 
Monongahela and Allegheny rivers and on and below Grant and Eleventh streets. 
Stop valves inclosed in suitable street boxes will be provided at frequent intervals 
in the mains, by means of which the air supply can be shut off from any section 
of pipe undergoing repairs, or while service connections are being made. At 
such times the air can be made to pass the portion of the main thus cut out. 
through the pipes in the adjoining streets, causing inconvenience to but few users 
of the power. Much annoyance could be averted by making service connections 
at night, or if made by day, appliances could be used which permit making con- 
nections to pipe lines without shutting off the supply. The estimate does not 
cover the cost of service connections, as they will be paid for by the consumers 
of the power, but does cover the cost of meters. Liberal margin has been al- 
lowed in the various items, and the following figures would undoubtedly cover 
the actual cost of construction. Allowance has been made for dividing the 
boilers and compressors into such units as to provide reserve power, available in 
case of accident or while repairs are being made. 

COST OF CONSTRUCTION. 

Real Estate $30,000.00 

Buildings 20.000.00 

Compressors erected on foundations with Condensers and attachments. 55.000.00 

Boilers 21,000.00 

Stack and Britchen 3.750.00 

Mechanical Stokers 4.375.00 

Circulation and Feed Pumps, Injectors, etc 4.000.00 

Cooling Apparatus 2.000.00 

Water Tanks 1,500.00 



3i2 TRANSMISSiOiSf. 

Coal and Ash Conveyors 4,000.00 

Pipe Lines and Distributing Mains 70,000.00 

Meters 5,000.00 

Engineering and Expenses of Organization 25,000.00 

Miscellaneous Items, including electric light plant and crane for power 

station 10,000.00 

Contingencies 19,375-00 

Total cost of plant $275,000.00 

COST OF OPERATION PER ANNUM. 

Interest on investment of $275,000 at 6 per cent $16,500.00 

Deterioration 4 per cent, of $275,000 11,000.00 

Taxes 3,500.00 

Fuel 5,000.00 

Salaries and Wages 16,500.00 

Repairs and Supplies 5,ooo.co 

Office Expenses 2,500.00 

Total annual cost of operation .$60,000.00 

It is estimated that the plant will deliver 1,100 h. p. for 3,000 hours, and 
200 H. P. for 5,760 hours per annum, or a total of 4,452,000 h. p. hours per annum. 
The annual cost of operation, divided by 4,452,000, gives 1.35 cents per h. p. per 
hour, or $40.50 per h. p. per annum of 3,000 hours. 

The cost of power to consumers would be graded somewhat, according 
to the amount used. This would not be a hardship to small users of power, be- 
cause to such consumers the power would be cheap at any reasonable price. To 
users of power in moderate quantities, the cost per h. p. per annum, including 
attendance, cost of heating and interest on cost. of motors and heaters would not 
be more than $50. 

For deterioration there will be laid aside each year out of the earnings, 4 
per cent, of the total investment, and this money placed at 3 per cent, compound 
interest will, in about 19 years, equal the capital invested, or sufficient to re- 
build the plant entire. It will be noted that the cost of operation would increase 
but slightly with considerable increase in the capacity of the plant, and also that 
the cost of construction would not increase in direct proportion to such enlarge- 
ment of the plant. If the building of a larger plant would be justified, the cost 
of power to consumers would be less than given. 

To compare the cost at which power could be furnished by compressed air 
with the cost as furnished by other means, I extract the following from our pro- 
ceedings, being estimates given in papers read by members of this society at dif- 
ferent times : 

Amount per h. p. per annum paid to the City of Pittsburg for operating 

hydraulic elevators (about) $700.00 

Cost of power per h. p. per annum in a large store having its own plant, 

15 hour service 128.44 

Cost in same plant corrected for 10 hour service 89.92 



TRANSMISSION. 313 

Estimated cost per h. p. per annum at which power could be furnished 
by a proposed hydraulic power company, with no allowance made in 

operating expenses, for taxes, or deterioration of plant 77-70 

Cost in same plant corrected for above omissions IGO.20 

Estimated cost per h. p. per annum at which power could be furnished 

by an electric power company capable of delivering 20,000 h. p 50.00 

The low cost at which power can be furnished by compressed air can only 
be approached by electricity working under the most favorable conditions. The 
rates paid for power to the electric companies in Pittsburg at the present time 
are excessive. ' 

EFFICIENCY OF THE SYSTEM. 

It can be shown theoretically, and has been proven in practice, that one 
cubic foot of free air, when compressed to about 90 pounds per sq. in., is capable 
of performing from 2,600 ft. lbs. to 3,000 ft. lbs. of work, when used cold. From 
actual tests it has been found that by heating the air this can be increased 40 per 
cent. Prof.Unwin states that the experiments of Reidler and Gutermuth show that 
heat thus applied is used five or six times more efficiently than if used in a good 
steam engine. The compressors, as above specified, have a combined capacity of 
12,000 cu. ft. of free air per minute. Deducting 15 per cent, of this for loss by 
leakage and friction in pipes, we have 10,200 cu. ft. of free air available for use- 
ful work; or expressing it in foot pounds per minute, we have 10,200+2,600 
+ 1.4=37,128,000; or in horse power, we have 37,128,000^33,000=1,125 H. p., 
which is 56 per cent, of the indicated h. p. in the steam cylinders of the com- 
pressors; assuming the efficiency of the motors where the power is used to be 
90 per cent., we have an efficiency of over 50 per cent, in the entire system, from 
the indicated horse power in the steam cylinders to the brake horse power in the 
motors. This compares favorably with electric transmission, which, under aver- 
age conditions, is about 58 per cent. Much higher efficiency than 50 per cent, 
have been given by writers on this subject, but the figures here given are based 
on the actual capacity of the compressors after due allowance has been made 
for internal friction and other unavoidable losses, such as leaking stuffing boxes, 
valves and pistons, and moje especially the loss occasioned by the heating of the 
air during compression. Moreover, the builders of the compressors will guar- 
antee the capacity as here given, and the estimates from two different firms 
showed practically the same indicated horse power in the steam cylinders of the 
compressors to produce the amount of air required. 

One thing to be noted in the use of compressed air is the fact that the loss 
caused by the fall in pressure resulting from friction in the mains, is partly made 
up by the increase in volume. In a hydraulic system a fall in pressure, caused 
by friction in the mains, results in a loss in direct proportion to the fall in pres- 
sure; the volume remains the same. The efficiency of the system can be con- 
siderably increased by using compound motors, in which the air would be heated 
before entering the motor and reheated between the first and second expansions ; 
the motor being somewhat similar to a compound steam engine with a receiver 
between the high and low pressure cylinders, the receiver in this case being a 
reheater. When the air is heated to increase the economy, the most efficient 
results arc obtained when moisture is added, which, by giving out its latent heat 



314 TRANSMISSION. 

in the motor, materially increases the efficiency. For this reason heaters are 
generally of the hot water style, wherein the air passes through hot water under 
pressure, and part of it goes to the cylinder of the motor in the form of steam, 

USES OF COMPRESSED AIR. 

Compressed air can be applied to such a wonderful variety of uses that a 
ready market for the entire power of the plant is almost assured, and the project 
would undoubtedly be as profitable in a financial way as it has been elsewhere, 
notably in Paris. The power would be used for the operation of elevators, elec- 
tric light plants, ventilating apparatus, pneumatic tools, and motors. It would 
also be used for parcel and cash conveyors, cleaning and cooling purposes; for 
the latter purpose either air direct from the mains, or exhaust air from the 
motors, would be used. For comparatively small addition to the cost of building 
the plant, a system of regulating clocks could be installed, and but very little 
power would be required to operate it. Some of the new office buildings in the 
East have been piped for delivering compressed air to the tenants, the same as 
they would be provided with hot and cold water. Compressed air only lacks the 
capacity to supply heat, to enable it to operate the entire mechanical plant of the 
modern office building. Heat would be supplied by the boilers in the building, 
but not being called upon for lighting or power purposes, would be operated 
only during the cold months of the year. In the ideal plant, however, heat would 
be furnished by the hot water system, and power and light by air — the cost of 
operation being thereby reduced to the minimum. 

The project could be still further enlarged upon. While laying the dis- 
tributing main, ducts could be laid for a parcel delivery system. Stations would 
be located in different portions of the city, where parcels would be received and 
sent through the chutes to the station nearest to the destination of the package, 
and the delivery be completed by messenger. 

It would be practicable to have street connections in close proximity to the 
fire plugs, and operate fire engines by air, which could then be built much 
cheaper, lighter in weight, less complicated in detail, and would be ready for 
immediate service at all times. In fact, the practicable applications of the power 
are almost unlimited, and the project would certainly meet with success and pay 
handsomely on the capital invested. It would increase our business and manu- 
facturing facilities and assist greatly in making Pittsburg a cleaner city and more 
desirable as a place of residence. These are factors in the making of a truly 
Greater Pittsburg. The building of a metropolis must consist of a more healthy 
and substantial growth than accrues from the annexation of surrounding villages 
and pasture fields. 

PNEUMATIC LOCOMOTIVES. 

Compressed air has been used with great success in the operation of loco- 
motives. When used for operating street cars or for hauling trains through 
tunnels or city streets, all the advantages of an independent motor are obtained, 
with none of the objectionable features of steam locomotives or electric cars. 
It is especially applicable in locations where sparking electric wires, fire and 
fumes of combustion must be avoided. 



TRANSMISSION. 315 

The following is a very brief description of the plant of the Susquehanna 
Coal Co. at Glen Lyon, Pa., where there arc two motors in operation. The air 

is supplied by a compressor of the three stage type, having steam cylinders 20 
inches + 24 inches, and air cylinders 12V2 inches, 9^ inches and 5 inches 
+ 24 inches, with water jackets and intercoolers, compressing the air to 600 
lbs. per square inch. The air passes through a line of 5 in. special strong pipe 
200 ft. to the head of the shaft, down the shaft 800 ft. and then along the gang- 
way about 3,400 ft., a total length of 4,300 ft. This pipe line has a capacity of 
580 cu. ft., and acts as a reservoir for the compressor. It is coupled together 
with threaded sockets which are counter-bored for a lead filling which is caulked. 
At intervals of about 200 feet, and at all valves and charging stations, flange 
couplings are used with lead gaskets, and the line is perfectly tight, being tested 
to 1,500 lbs. per sq. in. Charging stations are placed where required, and con- 
sist of a universal metallic coupling, which is attached to the check valve of the 
locomotive air tanks when a fresh supply of air is required. It requires about 
i^ minutes to complete the operation of charging the locomotive, and reduces 
the pressure in the main pipe line from 600 lbs. per sq. in. to about 570 lbs. per 
sq. in. A charge of air weighs about 380 lbs. The locomoitve is of the 4 wheel 
type, having cylinders 7 in. diameter by 14 in. stroke ; drivers, 24 in. diameter ; 
weight, 18,500 lbs.; length over all, 17 ft. 6 in.; width, 5 ft. 2 in.; height, 5 ft. o 
in. The air for propelling the locomotive is stored in two cylindrical steel tanks 
with a combined capacity of 130 cu. ft., and are supported by cast iron saddles 
resting on the frames of the locomotive. The air flows from the main tanks 
through a specially designed reducing valve into an auxiliary reservoir, and from 
thence through a throttle valve to the cylinders. The pressure in the auxiliary 
reservoir can be regulated anywhere from 30 lbs. up to 140 lbs. or 150 lbs. per sq. 
in., as required. The air in the auxiliary reservoir is maintained at a constant 
pressure, while in the main storage tanks it may vary from 570 lbs. per sq. in. 
down to the pressure at which the reducing valve is adjusted; when this pres- 
sure is reached in the main storage tanks, the air passes through to the cylinders 
without further reduction in pressure. 

The locomotive hauls 16 empty cars a distance of 3,700 ft. into the gang- 
way and returns to the shaft with 16 loaded cars with one charge of air, starting 
with a pressure of 575 lbs. per sq. in., and ending with about 100 lbs. per sq. in. 
The train of empty cars, including the locomotive, weighs 60,000 lbs., and the 
train of loaded cars, including the locomotive, weighs 166,000 lbs. The grades 
favor the loads. The locomotive runs from 25 to 50 miles per day, depending 
upon the length of the trip and time consumed in making up the trains at the 
terminals. This locomotive was lowered down the mine shaft a vertical distance 
of 800 feet without dismantling in any manner. Sometimes the circumstances 
are such that it becomes necessary to take the locomotive apart, lower it piece by 
piece, and reassemble them in the mine. 

Where it is practicable to use a heater on a locomotive, the efficiency is in- 
creased about 40 per cent. These heaters take the place of the auxiliary reser- 
voir, and consist of a tank containing hot water under pressure at a temperature 
of about 300 deg. F., through which the air passes before going to the cylinders. 



3i6 TRANSMISSION. 

The heaters are charged with steam while the storage tanks are being charged 
with air. 

Compressed air is also used for the propulsion of street cars, the air being 
stored in nests of Mannesman tubes. There are four of these tubes under each 
car seat, and are 9 inches in diameter by 15 ft. long, and are charged to a pres- 
sure of about 2,000 lbs. per square inch. The air is reduced in pressure by a re- 
ducing valve to about 140 lbs. per sq. in., and then passes through a hot water 
heater and throttle valve to the cylinders. The cars are of the four-wheel type, 
have the ordinary street car body, and are provided with the usual locomotive 
machinery, reversing gear, balanced valves and air brakes. They can be con- 
trolled from either platform by means of a fixture similar in appearance to a 
trolley car controller, and very compact. They are independent motors, have 
all the advantages claimed for storage battery cars, and compare favorably with 
the overhead trolley system in cost of operation. 



PRACTICAL APPLICATION OF HIGH RANGE COMPRESSED AIR 
POWER TRANSMISSION.* 



BY FRANK RICHARDS. 



I use the term high range to designate the system here referred to for 
convenience as it seems to fit the case, whether it has been used before or not. 
The system is called also the two-pipe system, on account of the return pipe, made 
necessary to convey the air which has done its work back to the compressor, the 
exhaust pressure being constantly maintained very much higher than that of tht 
atmosphere. The system has been put into practical operation in California and 
elsewhere in the far western portion of the United States, being known there as 
the Cummings system of compressed air transmission, the apparatus there em- 
ployed being under United States patents granted to Charles Cummings, of Oak- 
land, Cal. 

Under this system the compressor in full operation receives the air returning 
from rock-drills, pumps, hoists, motors, or whatever it is employed to drive, at a 
pressure considerably above that of the atmosphere, compresses it to a still higher 
pressure, and then sends it out again to do more work. The operation as thus 
stated is as simple as that of the ordinary air compressor, which takes in free air, 
or air at atmospheric pressure, and sends it out again at a pressure of, say, six or 
seven atmospheres. In compressing from one to seven atmospheres or in com- 
pressing from seven to 14 atmospheres there is no essential difference in the 
operation involved. 

If the compressor is to work at anything like the pressures last indicated 
there must, however, be some provision for first charging the system to the high 
initial pressure required, and also some means of governing or controlling the 
speed and output of the compressor according to the rate at which the air may be 
used at the other end of the system. The arrangements by which these results 



* American Machinist. 



TRANSMISSION. 



317 



are accomplished are worth looking into. Fig. 91 is a side 'elevation, Fig. 92 is an 
end elevation and Fig. 93 a plan of a duplex steam driven compressor. Of the 
general design of the compressor it is not necessary to speak. It will scarcely be 
maintained that it represents the best possible arrangement. The steam cylinders 
are at the left, Fig. 91, and the pull and thrust of the steam piston is transmitted 
directly through the yoke in which the connecting rod plays to the air cylinder. 
The body of the air cylinder is water jacketed and the valve chambers On each 
end have each a vertical partition, the inlet valves and pipes being on one side 
and the discharge valves and pipes on the other. The air being at normal atmos- 
pheric pressure throughout the apparatus we may start the compressor, referring 
principally to Fig 92, and as we proceed the functions of the pipes and connec- 
tions will reveal themselves. Both compressing cylinders are alike in construction 
and operation. At the beginning of operations we may assume the globe valve M 




FIG. 91. ; : FIG. 92. 

Side and End Elevation of High Range Air Compressor. 

to be closed and all other valves to be open. The free air will enter through 
valves K^ and L^ and the compression will continue until the pressure rises to, 
say, 100 pounds, if we assume that pressure for the lower limit of our working 
range. When the pressure of 100 pounds is reached valve N^ is closed by hand, 
separating the high pressure and the low pressure pipes, and the operation of 
compression then continues until the high pressure pipes are filled to the high 
pressure required, say 200 pounds, while the low pressure system remains charged 
at 100 pounds. The air inlet valves K^ and L^ are closed by hand and valve M 
is opened, allowing the 100 pound air to be delivered to both cylinders. The 
entire apparatus is now a closed system, with both the high and the low pressures 
as required, and ready for continuous action. A small pump U, shown in Fig. 91 
up at the right, replaces what air may be lost by leakage. This pump may be 
placed wherever most convenient and may be operated by connection with the 
main compressor or otherwise, and here requires no further mention. 

Attention is now called to cross pipe O. This pipe directly connects the 
high pressure and the low pressure pipes. Somewhere between the two pipes is 
located the valve O'. This is an adjustable pressure valve which may be set to 



3i8 



TRANSMISSION. 



open at any pre-determined difference of pressure, in this case lOO pounds, and it 
will not open until that difference exists, when any excess of air in the high 
pressure pipes is automatically discharged into the low pressure, thus constantly 
maintaining the required difference. The compressor may be charged or put in 
condition for continuous operation by the use of this automatic valve instead of 
by the hand operated valve N^. 

The operation of governing an air compressor, either under the system we 
are considering or any other, is distinctly different from that of governing a sta- 




FiG. 93. — Plan of High Range Air Compressor. 



tionary steam engine. The amount of power required may fluctuate in either case, 
but in that of the steam engine it is still usually necessary to maintain a constant 
rate of speed. In the case of the air compressor it is necessary to vary the speed 
according to the work. With our closed circuit of piping, and assuming the com- 
pressor at one end and the motor at the other, each running at such relative speeds 
tliat the difference of 100 pounds is just maintained between the two pipes^ if it 
should then happen that the motor should be run slower, or in any way should 



TRANSMISSION. 



319 



require less air to pass through it, then if the compressor still maintained its 
speed, the pressure in the high pressure pipes would become too great, while in 
the low pressure pipes the pressure would fall too low. The reverse operation 
would result as badly in the opposite direction. A centrifugal governor is pro- 
vided, as shown, to control the speed of the compressor when the demand upon 
it is up to its full capacity and prevent it from running away. This governor 
may also come into play in the earlier stages of the initial charging of the system, 
but is of no use at other times, the differential pressure governor being the usually 
operative controlling device. This governor, which it is scarcely necessary to 
describe in detail, is indicated in outline up at the left of Fig. 91. It consists of two 



■■H.I ' ■"■^•' : '!? 


c 


'^^■X-Z " 


r* !;",;.--.'W. ;> l^^^^^^BI 



Fig. 94. — High Range Air Compressor in Service. 



cylinders of different areas, say one twice that of the other, the two pistons being 
connected and moving together and by their movement operating a sliding steam 
valve and controlling the flow of steam to the steam cylinder. These governor 
cylinders standing vertical, and that of the larger area being above, with the 
smaller cylinder below, a small pipe connecting with the low pressure system 
is led into the top of the large cylinder, while a pipe from the high pressure sys- 
tem enters the bottom of the lower and smaller cylinder. The differences in pres- 
sures being compensated by the differences of piston areas, the Jiiston and the 
steam valve are stationary when the difference in pressures is normal, while if the 
high pressure increases the steam valves closes and slows the compressor, and if 
the high pressure falls while the low pressure increases then the steam valves 



-: TRANSMISSION. 

moves in the other directioii, more steam is admitted and the compressor runs 
^ster. The compresscM- being dnplex, with cranks at right angles, it wilL of 
cooTS^ start itsdf from ai^ position. The compressor for this system, it will 
thus be seen, leqoires littk conq>licatioo above that of the ordinary compressor. 

It is proper to say a little as to the actual practical workings of the system. 
As is wdl known, the nse of con^ressed air is perhaps better developed and bet- 
ter ^predated t^on the Padfic coast than anjwhere else in the United States. 
Some adnniaUe installations of the ordinary type are in operaticm there and 
some nofaUe instances of large plants and long distance transmission. It is not 
strai^e tiiat the two pipe system also shotdd find its fii^ onployment in the same 
section. It can scarcely be claimed for it that its possibilities have yet been all 
developed or that its ^plications have been other than crude and cheap. The half- 
tcHie herewith ^>eak5 for itself as to the conditions mider which it has been tried 
(or it would lave so sp<^en if the engraver had not taken such pains to make 
the scene re^>ectaUe). The cranpressor here shown is of different construction 
from that idiich I have described, bat it embodies the same two pipe principle. 
As to the resolts attained, there are not as yet any thorough, careful and precise 
tests to be referred to, and we most be content with statements such as the foUow- 
i^: 

"Two tests were made of three honrs each, one with tiie machinery run 
tmder the two pipe system, and the other with the same machinery run tmder the 
ordinaxy sy^cm. In eadi one the same machinery was used throug^ioaL This 
consisted of a duplex air conq>ressor with air cylinder 5x9 inches, and steam 
cylinder 6^ x 9 indies, and a water pump with air cylinder 45^:2 x 7 inches, and 
water cylinder 5x7 inches." These dimensions are not altogether clear and 
satisfactory, hat I give them as I have received them. The statement of com- 
paiative performance which follows b more intelligible. 

The ma c hine ry was mn for three hoars under the two-pipe, high range 
system. One of the fripes was then disccnmected and the same machinery was 
run under the ordinary system. That is to say, instead of exhausting into the 
return pipe, the exhausting was done into the atmo^here. The pump was em- 
I^oy^ in elevating water 80 feeL The first three hoars under the two-pipe system 
the pomp nnde 23JS}U revohitioas while the coaq>ressor made 16,735 revolutions. 
In the second three hoorsL, running onder the ordinary system, the compressor 
made 22:735 revolutions and the panq» 5,380." There was, of course, no such 
advantage as the figores given seem to indicate, but that tiiere was a great ad\-an- 
tagc seems dear. **In the two-pipe system we ran the pump about as fast as is 
consistent widi good practicev while the c(mq>ressor had to be run conq>arative1y 
dow. In the ordtnaiy syston we coold hardly mn the compressor fast enough 
to give snflkient air to the panq> to turn over^ We had great difficulty in running 
three hoars onder the ordinary system, owing to the fact that the temperature in 
the exhaost ports of the pomp came bdow the freezing point of water. We had 
to use petrc^eom to make the ptmap work. Of course, under the two-pipe system 
there is no chance of any ice being formed from the expansion of the air."* 

Hans C- Behr, in a bolledn of the California Mining Bureau, says : **The 
inddental advantage in the two-pipe system is that the pump engines, particularly 
if direct admg, can be operated under water until they wear ouL" He says also : 
*^To properly estimate the value of this system it most be compared to the rdieat- 



J 



TRANSMISSION. 



321 



ing system as to mechanical efficiency, first cost and simplicity of construction 
and manipulation." I have seen also enough other letters to probably convince 
any ordinary person that this system gives quite astonishing results. 



A SPECIAL STOP-COCK FOR COMPRESSED AIR PIPES. 

We illustrate herewith a special stop-cock that has met with great favor of 
late among the mines, for use in compressed air pipe lines. This cock is being 
manufactured and sold by the American Engineering Works of Chicago. It is 
made with iron body and brass plug ^ in., i in., i^ in. and ij^ in. in sizes for 




Fig. 95. — SrEciAL Stop-cock for Compressed Air Pipes. 



use in air pipes. A i-in. all brass cock is made for use in connection with air 
drills. The great advantage of this stop-cock over the ordinary form is that 
there is no possibility of workmen leaving it loose, with consequent and often 
considerable loss of air. In many forms of stop-cocks the plug is larger at the 
top than at the bottom, and is held in place by a nut at the bottom. Workmen 
will frequently loosen this nut, knock the plug up slightly in order to loosen it, 
to enable them to open or close the cock, and then leave it in a leaky condition. 
The stop-cock, as illustrated herewith, has the plug reversed, being larger at the 
bottom than at the top, and is held tightly in place by a spring. If it does not 
turn easily a slight knock on top of the square head will loosen the plug and 
enable it to be turned, but it will not be left in a leaky condition, for the spring 
will keep the plug well seated. — Engineering and Mining Journal. 



322 TRANSMISSION. 

MANNESMANN STEEL BOTTLE TEST. 

The public in general appears to have the idea that using compressed air 
stored at high pressures on street cars is dangerous. To prove how unfounded 
is this view, one of the bottles or tubes that is used in street cars was tested to 
destruction by hydraulic pressure on the loth inst. by Chas. G. Eckstein & Co. 
of New York, at the works of Messrs. Watson & Stillman, of this city. Prof. 
Jacobus, of Stevens Institute, assisted by Mr. Curtis W. Shields of our staff, 
conducted the test, the results of which are given below. Among those inter- 
ested present were Mr. Alfred Mannesmann, president of the Mannesmann Cycle 
Tube Co., Adams, Mass. ; Frank Richards, of the "American Machinist ;" John J. 
McCutcheon, Ass't Engr. American Air Power Co. ; Rudolph Allert, Sup't Con- 
sumers' Brewing Co. and Dr. Wm. Mettenheimer. 

The bottle was marked off into 7 equal parts and the measurements taken 
without pressure beginning at the bottom, were as follows : 2' 5 1-16", 2' 5 1-16", 
2' 5 1-16", 2! sy&", 2' 5 3-32", 2' 5 3-32'', 2' 5 1-32", outside diam. respectively. 
Length 5' 6j4" over all between perpendiculars. 

Under a pressure of 2,500 lbs. the greatest expansion was a little over 
1-16"; at 4,000 lbs. 3-32". When this pressure was removed the bottle returned 
to its original measurements. At 4,350 lbs. the greatest expansion was %" ; at 
4,550 lbs. 7-32", and the greatest permanent set noticed was 6-32". 

At 5,000 lbs. the length of the bottle had increased nearly %'\ and the 
expansion was 7-16"; at 5,280 lbs. %", at 5,730 lbs. 13-16". The bottle burst 
under a pressure of 5,760 lbs. The fracture was very clean, and not even a min- 
ute particle of the metal flew. The fracture extended from the neck a distance 
of 2' ^" down the side of the bottle. 



STORAGE OF AIR IN BOTTLES. 

A good deal has been written of late in the newspapers about the danger 
to which passengers may be subjected when riding in cars propelled by com- 
pressed air because of the storage of air under high pressure. Until recently 
experiments in the line of pneumatic traction were confined to air at moderate 
pressures, mainly because a safe bottle or receiver was not available. In de- 
signing a vessel in which to store the air, it is necessary to consider the question 
of weight, and as the air pressure was increased, the weight of common receivers 
became so great as to be prohibitive. Pipes of wrought iron or steel were all 
right when made of extra thickness, but the weak point was in the cap or joint 
at the end of the pipe. During recent years there has been imported a weldles.s, 
cold-drawn steel tube which has served the purpose very well. This tube is 
known as the Mannesman bottle and is made in Germany. Its safety lies in the 
fact that it is drawn from a solid billet of steel, hollow throughout with rounded 
ends forming a vessel of uniform strength and with no joints or welds of any 
kind. One end of the Mannesman bottle is tapped for a pipe of small diameter 
which connects with the interior and which serves as an outlet or inlet for the 
compressed air. This form of bottle is a safe vessel for air at pressures of 3,000 



TRANSMISSION. 323 

pounds per square inch, and it is so designed that a number of these bottles, each 
about the length of the space under the seats of a street car, are laid side by side 
and connected at one end, thus storing enough air, as in the case of the Hardie 
car, to run approximately 25 miles. 

Some experiments have been made with cold-drawn bottles made of nickel 
steel, which it is claimed will store air at 5,000 lbs. pressure per square inch, 
and as the tensile strength of nickel steel is high, bottles made of this material 
should be able to safely carry large volumes of compressed air in a small space 
and without the handicap of serious weight. Now the safety of a steel bottle 
carrying compressed air is a simple question of engineering. A boiler carrying 
steam at a pressure of say 100 lbs. per square inch is less safe than an air bottle, 
because the boiler is composed of joints and rivets, and carries superheated 
water, all of which being subject to variations of temperature, thus increasing 
the uncertainty as to the factor of safety. The reserve force contained in super- 
heated water in a boiler is enormous. Should a break occur and the steam be 
released, this water is converted into steam almost instantly, and acts in a sense 
like gunpowder or dynamite producing destruction in its path. The air bottle is 
practically at all times subject to a uniform temperature. It is designed to stand 
a certain pressure, and if properly tested before use and a factor of safety estab- 
lished beyond its working strains, there remains but little uncertainty or danger 
in its use. As a matter of fact, these bottles are easily tested before use, and 
engineers agree that in a vessel of this kind it is not necessary to establish so 
great a factor of safety as with boilers or other vessels which are subjected to 
changes of temperature and more or less varying strains. In a boiler, for in- 
stance, the feed water may run low and by sudden contact of cold water on hot 
plates the normal pressure may be momentarily very much increased. No such 
conditions can exist in the case of the steel bottle. 

A better comparison with the air bottle is the strain upon a floor beam or 
the truss of a bridge. One might claim that a bridge is dangerous because it is 
subjected to hundreds or thousands of tons strain, yet this bridge when properly 
designed is intended to carry this strain and its strength of material is propor- 
tioned accordingly. It is customary in bridge construction to allow a wide mar- 
gin or liberal factor of safety, because of vibration and other conditions which 
cannot be foreseen or estimated and which do not exist in the case of the air 
bottle, A cast iron column, even with a liberal factor of safety, is less likely to 
be safe than an air bottle, because blow holes may exist in cast iron beneath 
the surface, while with soft cold-drawn steel the material is uniform throughout. 
It should not be claimed, of course, that steel air bottles cannot be broken or that 
they are absolutely safe against explosions. Nothing in engineering is safe to a 
point of certainty, but it can safely be claimed that in the steel bottle the elements 
of uncertainty are small and easily controlled ; that the bottles are not subject to 
deteriorating influences, as they are surrounded by free air on the outside and 
compressed air on the inside ; that when made properly and carefully tested they 
may safely be used to carry air pressure strains of one-half the figures at which 
they are tested, and as it is quite possible to provide these vessels with blow-off 
valves they may be made practically safe. 

Even though an air bottle should explode when carrying air at pressures of 
st;veral thousand pounds to the square inch, it is not likely to be as destructive 



324 TRANSMISSION. 

as is usually supposed. These bottles are arranged in a series in some respects 
like the water tube boiler, which is considered to be the safest form of boiler 
made. Water tube boilers do not explode. There have been instances where one 
or more of the tubes has been disrupted, but the effect is only local, while with 
common cylindrical boilers, explosions have been frequent and the results serious. 
Air when released shrinks rapidly in volume, because of a rapid lowering 
of temperature. This tends to reduce the force of explosion. The effect would 
very likely be local and of very short duration, as the air once released is soon 
discharged. 

FREEZING IN COMPRESSED AIR. 

Freezing in compressed air pipes and passages is more frequent in winter 
than in summer, not entirelj'^ because of the low temperature in winter, but be- 
cause of the increased density and saturation of the atmosphere. On a cold day 
in January which follows warmer weather, the steam discharged from exhaust 
pipes rises and floats for a considerable distance before it becomes dissipated. 
It acts in this respect like smoke. This condition is due to an excess of moisture 
in the atmosphere because of a shrinkage of volume produced by reduced tem- 
perature. When the atmosphere is dry it soon takes up and carries in suspen- 
sion the steam globules. The same reason accounts for the long wake or foam 
following a ferryboat in crisp, cold weather, the foam being nothing more than 
aerated water, which is soon scattered, and partly absorbed by the atmosphere, in 
dry weather. In a compressed air installation the air-discharge pipes are usually 
exposed, and are like surface condensers, reducing the temperature of the air 
which passes through them. If this temperature is reduced below the intake 
temperature, or the normal atmospheric temperature, there will be a coating of 
frost deposited on the interior walls of the conduit. The same causes which de- 
posit frost on a window-pane, or which condense moisture on an ice-pitcher, are 
responsible for the clogging up of the interior of a compressed air pipe. It is 
well to cover the pipes, and it is still better to enlarge them. A cheap trough, 
carrying sawdust or manure, preferably the latter, is a good preventive. A large 
pipe will last longer without clogging through frost for reasons that are obvious. 
When it is practicable it is best to place all air-receivers out of doors in order 
to effect as much condensation as possible before the air reaches the conduit. 
This helps to dry the air, and in some cases more efficient drying can be accom- 
plished by passing the air through a comb or radiator of pipes submerged in 
cold water, and provided with proper means by which the condensed water is 
drained off. The aim in all cases should be to reduce the temperature of com- 
pressed air to as low a point as possible before it is started on its journey. 

Freezing in exhaust passages is more difficult to overcome, but if the air 
is properly dried at the compressor station, the difficulties about the exhaust will 
be minimized. All exhaust passages should be large and free of access. It is 
well not to use exhaust pipes except such as are bell-mouthed or funnel-shaped. 
As far as practicable, use wood or other non-heat-conducting substances around 
the exhaust. In pumps, a little water admitted from the column to the valve 
will prevent freezing in the exhaust, because the water gives off its specific heat, 
and mechanically aids in cutting away the frost. 



TRANSMISSION. 325 

FREEZING. 

Lehigh & Wilkesbarre Coal Co. 

Wilkesbarre, Nov. 18, 1898. 
Gentlemen : 

In reply to your inquiry relative to the use of compressed air for operating 
pumps, we beg to state that we have no trouble whatever to keep them from 
freezing, as we insert a small pipe, or jet, in the pump close to the valve and 
inject hot water or steam, which effectually prevents freezing. In the summer 
time we use water just as it comes from the reservoir. Trusting that this will 
be of service to you, we remain, yours very truly, 

W. J. Richards, 
General Superintendent. 

The foregoing letter was addressed to a manufacturer of air compressors 
and is published here because it is practical. At this season of the year when 
freezing is common and when so many people are using compressed air to run 
pumps, it is of interest to know how to prevent freezing in the exhaust. This 
is a subject which the readers of Compressed Air will recognize as rather promi- 
nent in our thoughts, because we know that compressed air has been "turned 
down" on many occasions because of the complaint that it gives trouble through 
freezing. As it is generally admitted that compressed air as a power is supreme 
in mines and as pumps are largely used in mines, it is natural that the miner 
should wish to operate his pumps by compressed air. He is doing this in many 
cases under disadvantages because of freezing. In the piston pump the chief 
trouble from freezing is usually in the exhaust, which is gradually choked by 
ice. Of course, the first thing to do is to provide a free exhaust for the pump 
which uses compressed air; by free exhaust we mean do not connect any pipes 
to it and have the exhaust as large as is practicable. 

In England they advise bell-mouthing the exhaust, that is, inserting in the 
exhaust a fitting or pipe which is shaped like a bell. Our experience has taught 
us that it is best to insert nothing in the exhaust, but to have it as free and open 
as possible and to turn one's attention to preventing the accumulation of ice by 
either reheating the air before it enters the pump, or by inserting water or steam. 

Reheating is obviously the best plan to follow, because it adds to the 
efficiency of the air by increasing its volume, due to expansion through heat. 
The objection to reheating in the mine is that the products of combustion are dis- 
charged in the mine and interfere with the ventilation. This is true only where 
the reheating is done on a large scale, but it is seldom necessary to reheat on a 
large scale, as what is wanted is simply an addition of 25 or 30 degrees of tem- 
perature, and if this is done properly it will require but a small quantity of fuel 
and will produce no more hurtful results than the burning of half a dozen miners' 
lamps. 

If electricity is used in the mine it will serve a useful purpose by putting in 
resistance coils in contact with the air, thereby heating it electrically. It costs, 
of course, more to heat electrically than to heat directly by fuel, but compressed 
air is sensitive to heat; a little heat adds largely to its volume, and when other 
conditions are considered, it is safe to say that reheating electrically pays. 



326 TRANSMISSION. 

A candle burning in a compressed air pipe will burn with greater intensity 
and will give off a larger heat effect than when burning in free air. The theoreti- 
cally perfect reheater is that which burns a candle or some other substance within 
the air. A miner's lamp has been placed in a four-inch pipe and has warmed a 
considerable volume of air. It is difficult, of course, to arrange an apparatus by 
which this form of reheating is made practical, but that some one will devise such 
an apparatus, we have no doubt. There is no such thing as burning the air by 
internal reheating. The effect is simply to change the conditions by adding car- 
bon and producing air and gas both of higher temperature, hence both more 
efficient when used as power. 

External reheating, that is, simply applying heat to the external surfaces of 
vessels containing compressed air, is the commonest form of reheating, and may 
•DC used even in mines. Small reheaters are now furnished by builders of air 
compressors and are placed near the valve of the pump, these heaters being so ar- 
ranged that the products of combustion are carried off, or in some cases they are 
simply discharged in the mine, but little fuel being required. These reheaters are 
sometimes arranged to burn gasoline and other oils. Where pumps are used 
without reheaters good results may be obtained by injecting water or steam on the 
plan mentioned in Mr. Richards' letter. Both water and steam carry a good deal 
of heat, that is, the specific heat is high compared with the specific heat of air, 
hence small quantities injected into the air directly at the valve or inlet serve a 
useful purpose in giving out heat and thus preventing freezing. It is not always, 
of course, convenient to get hot water and steam down into the mine at the point 
where the pump is located, but one may be surprised to know how far steam and 
hot water may be carried. If convenient, the pipe carrying the hot water or 
steam should be inserted within the compressed air pipe, so that the heat given 
off through condensation will be imparted to the compressed air. If the pump 
is too far away use cold water, for it is strange to say that even cold water will 
prevent freezing in pumps using compressed air; this is because the water gives 
off its heat to the air during expansion, and in addition to this, it acts as a me- 
chanical scourer in washing away the ice as it accumulates in the exhaust pas- 
sages. 



FREEZING. 

In a recent conversation with Mr. Geo. E. Ames, Supervising Engineer of 
the Anaconda Copper Mines in Montana, the question of freezing in compressed 
air pipes was brought up. Mr. Ames is a practical man, having recently taken 
charge of the Anaconda mines after an experience of i8 years with the Union 
Iron Works, San Francisco. Large volumes of air are used in the Anaconda 
mines, compressors being installed at different points, with an aggregate capa- 
city of 50,000 cubic feet of free air per minute, delivered at 80 pounds pressure 
per square inch. Among the installations is one where the compressed air after 
leaving the generating station is conveyed over ground a distance of several thou- 
sand feet and then carried down a shaft into the mine. 

During the winter months it was found that at times it was difficult to 
get air pressure in the mine, and Mr. Ames set about to discover the cause. Be- 



TRANSMISSION. 327 

ing an engineer he looked at the case from a theoretical as well as a practical 
standpoint, and discovered that the air pipe was in fact a surface condenser, the 
cold Montana winds keeping it at a low temperature, and the hot compressed air 
on the inside coming in contact with the cold surface of the pipe was reduced 
in volume and temperature, and as it went along it deposited its moisture on the 
interior surfaces. Air at all times contains moisture. It is called comparatively- 
dry when the humidity is 50 per cent., which means 50 per cent, of the quantity 
of water required to saturate a given quantity of air. At times it is as high as 90 
per cent., and even more. This water is in the air, though we cannot see it, and 
it is just as certain to be condensed to a visible and a troublesome liquid when 
the temperature is lowered, as steam may be converted into water. It is alto- 
gether a question of temperature. Steam is in a condition of vapor only because 
it is held up by heat. The air we breathe passes over water surfaces and absorbs 
moisture, just as the water is taken from wet clothes while hanging on the line, 
and the warmer this air is the more moisture does it take up. 

This water is carried around with the air and up into higher regions, 
where it meets with cold currents and is condensed into clouds. These clouds 
represent nothing else but the visible moisture which is present in the air drawn 
into a compressor, and it is certain to form a cloud and rain, either in the air re- 
ceiver, the pipe line or the rock drill or pump that uses the air. This is a process 
of nature, and knowing the cause, as Mr. Ames did, it was not difficult to find a 
remedy. This he found by putting in a series of old boilers outdoors near the 
engine room. The air at 80 pounds pressure and hot was passed from one of 
these boilers to the other until its temperature had been lowered to the initial 
point, and when it started up the hill it was practically of the same temperature 
as the pipe line, and it had left its moisture, or a large portion of it, behind. Old 
boilers when strong enough are especially well suited for use as compressed air 
condensers, because of the large metallic surface exposure through the shell 
and the flues. The compressed air passes around the tubes and the free winds of 
winter blow through them. It is best to so place these boilers that they will get 
plenty of wind. It is better to put them in a horizontal than in a vertical posi 
tion, and if wind is not available, use a blower, or better still, a cold stream of 
water. If practicable submerge the receivers. Suitable means should, of course, 
be provided for trapping the water. Pet cocks or globe valves are sometimes 
used, but water traps working automatically will serve the purpose better. It is 
not necessary, however, as some suppose, to take the water out as fast as it is 
formed, for as long as the temperature of the water is lower than that of the air 
there can be no absorption of water by the air. This simple remedy, which Mr. 
Ames has applied at the Anaconda mines, might save time and money at other 
places, and it is mentioned here hoping that it may have this result. 



FREEZING. 

As the cold weather approaches we wish to call attention to certain pre- 
cautions which may be applied to compressed air installations, and which will 
prevent the annoyance and expense of freezing. Makers of air compressors of 
the compound type furnish intercoolers, which are placed between the air 



328 TRANSMISSION. 

cylinders, and which serve to reduce the temperature of the air, as it passes 
between stages of compression. These intercoolers are nothing more than 
tubular condensers, commonly called surface condensers, the water circulating 
around the tubes, through which compressed air passes. In some of these the air 
passes on the outside of the tube and the water on the inside. However this may 
be, the principle involved is the same. 

These intercoolers require about i pound of water for each cubic foot of 
free air, the air passing at a pressure of 60 pounds per square inch. These 
coolers serve just as important a purpose as after coolers, as they do as inter- 
coolers, and there is quite as much reason for after cooling-compressed air as for 
cooling it between stages, because the after cooler, when properly installed, 
should bring down the temperature of the air to the original point ; that is, to the 
temperature of the atmosphere, and in this way moisture will be deposited 
before the compressed air is started through the line pipe to the work. If the air 
is started on its journey hot, and it traverses a line of pipe long enough and 
sufficiently exposed to reduce its temperature, we will have the conditions of a 
long drawn out condenser, moisture collecting on the inside of the pipe to form 
water and ice, at times completely closing the tube, through the incrustation on 
the inside. Now, in order to get this condensation, the temperature of the air 
must be reduced, and if we reduce the temperature at the receiver as low or lower 
than it is on the outside, there will be no chance for further reduction until the 
air is expanded. It is quite possible at certain seasons of the year to obtain 
such thorough after-cooling as to prevent freezing even in the engines during 
expansion, for we may safely say that if the temperature of the air never goes 
below that to which it is brought in the after-cooler, there will be no trouble 
from freezing, and it is quite impossible to get too low a temperature in the after- 
cooler, because no matter how we may shrink the air by cooling, we are all the 
time drying it, and when we start it through the service pipes and it meets there 
higher temperatures, we will then be reheating under natural conditions, the air 
taking up heat from the atmosphere without expense and after having been dried. 



West New Brighton, S. I. 
October 29, 1899. 
Editor Compressed Air: 

Will you kindly publish in CoMrRESSED Air a feasible method of testing 
a pipe line for leakage? 

The line in question supplies a dozen or so of Pedrick & Ayer Hoists, and 
it comprises a two-stage compressor 12 in. x 8 in. x 12 in. stroke, has no reser- 
voir, but compresses directly into the pipe line. 

C. Lee Straub. 

There are a number of factors which should be given before an accurate 
answer can be made. Using the data mentioned, it seems that the most satis- 
factory method would be about as follows: 

If the pipe line has valves at all branches, and a valve between the com- 
pressor and the beginning of the pipe line, the branch valves should all be closed 
and the compressor run until the air pressure in the transmission line is at the 



TRANSMISSION. 3^9 

maximum for which the machinery was designed. The valve between the com- 
' pressor and the pipe line should then be closed, and the full pressure in the pipe 
line noted. 

If there are no leaks it would seem that the pressure would hold up for a 
considerable time, and the time required for the pressure to drop from maximum 
to, we will say half pressure, will be a measure of the amount of leakage. 

Another way, although not as satisfactory, would be to shut the system 
down, or make the test when it can be shut down without inconvenience, and 
pump the transmission line full of water up to the maximum pressure. Leaks 
would then be indicated by wet spots. If there are no valves at the branches 
and the air is allowed to pass through flexible connections to the hoist, and is 
shut off by the hoist valves, this method would not, be advisable. The air 
method, however, could be used in exactly the same way, or the flexible air 
pipes could be disconnected and cups screwed on the branches. 

Another method in very common use is to place oil around the seam or 
joint in question and in case of a leak the air will blow bubbles of oil. Applica- 
tion is easily made by means of the ordinary "squirt oil can" used around ma- 
chine shops. 

The soapsuds method is perhaps the simplest. Take a strong solution of 
soap and water and with a clean paint brush apply the suds to the pipe, begin- 
ning at the compressor and following to the last appliance. Wherever there is a 
leak, bubbles will appear. Mark these places with chalk for future attention. 



Editor Compressed Air: 

The volume of discharge of compressed air at terminal pressure from a 
pipe varies inversely as the square root of the density of the air at initial pres- 
sure. 

The volume of discharge of compressed air from a pipe decreases when the 
initial pressure is increased, and increases when the initial pressure is decreased; 
the loss of pressure being maintained constant in both cases. 

The volume of free air equivalent to the discharge of compressed air from 
a pipe increases with the increase of the initial pressure, and vice-versa, the loss 
of pressure being maintained constant throughout. 

It is very important in the case of problems relating to the flow of air 
in pipes to bear clearly in mind whether the flow of free or of compressed air 
is being considered, as many of the conditions and effects are absolutely reversed 
in the two cases. 

"Free air" does not flow in a pipe, therefore the discharge from a pipe 
cannot be said to be such or such a quantity of "free air." 

It is often said that the loss of pressure in a pipe is proportional to its 
length. This is true only when it refers to the discharge of air under pres- 
sure (not free air) from a pipe. When the equivalent volume of free air dis- 
charged is taken into consideration (as is usually done), the loss of pressure 
caused by friction in the pipe is much greater in proportion as the length in- 
creases. Thus, if the loss of pressure at the end of looo feet of pipe, with an 



330 TRANSMISSION. 

initial pressure of 60 lbs., is 5 lbs., it will 'be 20 lbs. at the end of 2500 feet, and 
not i2j^ lbs., which would be the proportionate loss. William cox. 

New York. 



Editor Compressed Air : 

Could you give me any information about water getting in the air of a 
compressed air pipe line? We drain our receiver every three or four days, but 
do not get any water to speak of. The air is piped about 300 feet. T. R. H. 

WiLKESBARRE, Pa. 

To thoroughly deposit the moisture from the air of your compressed air 
pipe line before it leaves the receiver, you will find it necessary to cool the air in 
the receiver to at least a temperature of the surrounding atmosphere. A simple 
illustration of why this is so would be the falling of dew during still evenings in 
the warmer seasons; during the day the air becomes heated and at all times has 
more or less moisture in it; during the evening this same air becomes cooled to 
what is known as the dew point and the moisture is condensed and deposited as 
dew. To apply this to compressed air : the air becomes heated during compression 
and the moisture is held in a form of vapor; if the air is cooled before leaving 
the receiver this moisture will be condensed and deposited there in an amount 
directly proportional to the lowering of temperature. If you desire to avoid all 
water in the pipe line, you should cool the air in the receiver lower than the tem- 
perature of any surface it may come in contact with in passing along the line. 

In laying a compressed air pipe line it is highly advisable to select the 
coolest possible position for a receiver, say where it is shaded and the wind can 
pass around it or when water is at hand immerse it. By putting additional re- 
ceivers into the line and so locating and constructing them as to cool the air be- 
low its initial temperature, you will be able to overcome your difficulty. 

An editorial in the November, 1898, issue of Compressed Air (page 326 
of this book) describes the cooling system in the Anaconda Copper Mines, where 
numerous receivers in the form of old boilers are used with a success. 

Compressing air by the Compound system makes the discharge into the 
receiver at a much lower temperature than in single stage compression. This 
would also help you to overcome your difficulty. 



USE. 



331 



USE. 



HISTORY. 



From historical research it appears that compressed air for conveying pas- 
sengers has always been under consideration. Nearly all experiments have 
served to prove the mechanical power of the atmosphere, and the question, how 
it could be converted into a motive power, available for the conveniences of so- 




"^'^^.PNEUMATICa.^" 



FIG. 96. 



ciety, has been a problem of great interest to engineers. More than two cen- 
turies ago the notion was entertained of producing motion economically for the 
purpose of transit by means of the pressure of the atmosphere. The original 
thought may at least be traced back with certainty to the celebrated Dr. Papin. 
In the year 1810, a proposal was made by Medhurst, the Danish engineer, to put 
letters and goods and passengers in a canal, 6 ft. high and 5 ft. wide, and con- 
taining a road of stone and iron, and project them by means of atmospheric 
rarefaction and condensation. 



332 USE. 

In 1824, an Englishman, Mr. Vallance, made a similar suggestion. His 
daring plan was to connect Brighton and London by means of an enormous tube, 
through which, by pumping out the air, carriages were to be propelled with the 
velocity of a cannon ball. Other plans of equally novel character were con- 
sidered at various periods. 

The Pneumatic Parcel Despatch Company, of London, about the year 
1865, successfully worked a pneumatic line while it was designed for parcels, 
was capable of carrying passengers. (See Fig. 96.) 

The construction of the tube between Euston Square Station and the 
Northwestern Post Office in Eversholt, is described as most simple, cheap and 
effective, and reflected great credit upon its engineer, Mr. Rammel, for the ease 
and certainty with which the air from the fans sends one oi* more carriages, 
heavily laden, from one end to the other. Other demonstrations were made on 
this same line. At the Polytechnic of London, a little model of wood was con- 
structed about 20 feet long. There were two carriages, the passengers consisted 
of a party of white mice, and they were blown from one end to the other by 
means of a blast of air. 



MEN PROMINENT IN COMPRESSED AIR DEVELOPMENTS. 

Two conditions are always prominently connected with the development of 
every new and useful thing, whether it be a machine or the useful application of a 
new science — men and money. It is usual for use to talk of the lack of means as 
the excuse for failure to bring a new thing to the paying point, but the right kind 
of a man, the genius to handle each particular subject is of greater importance 
than money. Good and useful things have been produced by men working practi- 
cally without means, but money has never built up a good thing without the aid 
of the man of brains. 

Compressed air, though as old as the hills, is a new thing in its usefulness 
to mankind. This century, and we may also say this decade, is the compressed air 
era, and yet the useful application of this power has become so general, that we 
appear to be only beginning to enter this wide field of usefulness. American men 
and engineers are responsible for a large share of this. French, German and 
English engineers and professors are greater theorists, and have built for us the 
foundations on which practical work has been laid. The Popp system in Paris, 
deficient as it is from our standpoint, has pointed the way to better things. It was 
was this system which first attracted Professor Riedler's attention to compressed 
air. The writings and inventions of Professor Reidler entitle him to rank at the 
top among pneumatic engineers. He has been spoken of as the highest authority 
on pneumatics in Europe. 

This title might perhaps be disputed by Professor Unwin, of England, who 
though less inventive than Riedler, is quite his equal in knowledge of pneu- 
matics, and whose thoroughness and exhaustive capacity for work entitles him to 
rank among the greatest of living engineers. Professor Kennedy has also taught 
us much that we know about compressed air. 

The reader of this publication will be glad to see the portraits of those who 
have accomplished so much, and who are already well known by reputation. Our 



r 



USE. 



333 



gallery is necessarily not complete, notably so in that it does not contain the pic- 
ture of Mr. Ebenezer Hill of Norwalk, Conn,, our highest authority on this sub- 
ject, Mr. Hill is a rare combination of the engineer and business man and an 
inventor who has designed standard machinery. He has been intimately con- 
nected with compressed air for perhaps twenty-five years, and in the development 
of the compound air compressor he is entitled to the first rank. Mr. Hill long 
ago saw the importance of compound compression, and he adhered to it at a time 
when he stood alone. To-day every engineer who knows anything about the sub- 
ject recommends compounding, and all makers of the first class furnish compound 
machines. 

Mr. Addisen C. Rand was born in Westfield, Mass., in 1841. He early 
became interested in the practical applications of compressed air through his 
connection with a powder manufacturing concern, which naturally gave him an 




FIG. 97. — ADDISON C, RAND. 



FIG. 98.^3. C. BATCHELLER. 



acquaintance with the needs of improved drilling and mining machinery. This 
interest took him into the field of manufacturing rock drills and later air com- 
pressors. The large experience gained in this field made him one of the best 
known compressed air men. 

Mr. Rand died on March 9th, 1900, and at that time was President of the 
Rand Drill Company and a Director of the Laflin Rand Powder Company. 

Mr. B. C. Batchcller has been called the Edison of pneumatic sciences. He 
is, as his portrait indicates, a young man of determination and ability. He is 
best known in connection with the pneumatic despatch system of the Batchcller 
Pneumatic Tube Company, which has been adopted by the United States Gov- 
ernment. The details of this system, designed by Mr. Batchcller, show that 
practical originality which usually denotes the successful mechanical en^ineef, 



334 



USE. 



Mr. H. -D. Cooke has fought compressed air battles as a gallant knight : 
Compressed air has been his shibboleth. His work has been mainly of a business 
nature in connection with the promotion of pneumatic traction companies, and it 




FIG. 99. — HENRY D. COOKE. 

is probably due more to his personality and strength than to anything else, that 
the use of compressed air for street cars has been kept alive in America. 

Mr. F. A. Halsey is a well known engineer and inventor. Shortly after 
graduating from Cornell University he began work with the Rand Drill Company, 
where he invented the "Slugger" rock drill. Among other things he has invented 




FIG. 100. — F. A. HALSEY. 



a mechanical valve motion for air compressors and a pneumatic pump. He has 
published two works, "Slide Valve Gears," now in its fifth edition, and "Locomo- 
tive Link Motion." His paper entitled "The Premium Plan of Paying for Labor," 
read before the American Society of Mechanical Engineers in 1891, has been 



USE. 



335 



widely quoted. He is, perhaps, our best authority on valves. He is a close student, 
thoughtful and accurate and an acknowledged authority on pneumatics. 

Mr. Robert Hardie, the inventor of the Hardie Air Motor, is a Scotchman 
by birth, though in all other respects an American. Air, especially in its use for 




FIG. lOI. — ROBT. HARDIE. 

traction, has been Mr. Hardie's hobby. He designed the motor which was used on 
the elevated road in New York in 1879, and has recently built air motors for 
street car work, Mr. Hardie had much to do with the design of the De Larvergne 
Refrigerating Company's machinery: His mechanical ideas are marked by much 
individuality, the element of simplicity being prominent. It is doubtful if any one 




FIG. 102. — GEN. HERMAN HAUPT. 



has had as much experience as Mr. Hardie in pneumatic traction, and he is an 
acknowledged authority on the subject. 

General Herman Haupt is a well known engineer. Graduating from West 
Point as a military engineer, the General has had a most extended career in field 



336 



USE. 



work, railroad construction, bridge work, as professor of mathematics and civil 
engineering, general superintendent and chief engineer of railroads, etc. His at- 
tention was first attracted to compressed air in 1879. Since then he has been 
identified with pneumatic traction, as president of the General Compressed Air 




FIG. 103. — GARDNER D. HISCOX. 



Company. He has published several works, among them "General Theory of. 
Bridge Construction," and "Haupt on Motors." 

Mr. Gardner D. Hiscox, is a distinguished hydraulic and pneumatic 
engineer, and is at present on the staff of the Scientific American. Mr. Hiscox 
has had a most extended experience in mechanical construction, is very fertile in 
expedients and has a fund of information at his fingers' ends, based on practical 




FIG. 104. — J. H. M CONNELL. 

contact with work. As an engineer he combines the theoretical and the practical, 
and is well posted and a safe adviser on pneumatic and hydraulic subjects. 

Mr. J. H. McConnell is the efficient superintendent of motive power of the 
Union Pacific Railroad at Omaha, Neb. His paper read before the Western Rail- 



USE. 



337 



road Club (Compressed Air^ Vol. I, No. 2) showed a knowledge of the practical 
application of air, which has entitled him to rank as one of the most useful 
students of this subject. Mr. McConnell saw the possibilities that were dormant 
in compressed air, and he went to work to develop machinery for its use. This 
he has done in a most extended way on the Union Pacific road. 

Mr. R. A. Parke, is a well known mathematician and engineer, young, able 
and progressive. He is especially prominent among railway men, because of his 
connection with the Westinghouse Air Brake Company. He is a recognized 
authority on compressed air and especially in connection with air brake service. 
Mr. Parke has designed and patented a system of air brake traction which has 
been worked experimentally at Albany, N. Y. As an inventor he is extremely 
conservative, but for this his traction system might have been pressed forward by 
capitalists. A paper read by Mr. Parke before the New York Railroad Club in 





FIG. 105. — R. A. PARKE. 



FIG. 106. — WILLIAM PRELLWITZ. 



1894, entitled "Economy in Compressed Air Transmission for Commercial Pur- 
poses and for Air Brake Purposes," has been widely quoted and is an able contri- 
bution to our literature on this subject. 

Mr. William Prellwitz is in charge of the engineering department at the 

shops of The Ingersoll-Sergeant Drill Company. His training in connection with 

^lir compression, especially in the design of pneumatic machinery, has been 

W ' ough and extensive. Engineering comes natural to him, and he belongs to that 

' class of thinkers on the subject, whose ideas inspire confidence. Mr. Prellwitz 

thinks to the bottom of every subject brought to his attention ; a ready and expert 

free hand draughtsman and one of our best authorities on pneumatic engineering. 

His paper entitled "Compressed Air; Its Production, Transmission and Use," 

published in Vol. H., No. 7, of Compressed Air (page 67 of this book), is a 

compendium on the subject and an education to a student of compressed air 

literature. 



338 



USE. 



Mr. Whitfield P. Pressinger was formerly Secretary of the Qayton Air 
Compressor Works. He has written several magazine articles on compressed air, 
and his connection with the Clayton Company has given him a wide experience 




FIG. 107. — WHITFIELD P. PRESSINGER. 

in pneumatics. It has been mainly through Mr. Pressinger's active management 
that the Clayton Compressor is so widely known. At present he is associa.ed 
with the Chicago Pneumatic Tool Co. 

Mr. Frank Richards stands at the top among pneumatic engineers. A 
voluminous writer on the subject, clear and interesting in his style and combining 
the theoretical with the practical. Mr. Richards is a trained mechanic, having 




108. 



-FRANK RICHARDS. 



been at one time the superintendent of the shops of the Ingersoll-Sergeant Drill 
Co. He is at present associate editor of the American Machinist. His book on 
"Compressed Air" has had a large circulation, and contains more information or 
this subject than any other American publication. Personally Mr. Richards is of 
an extremely modest nature, popular with all his associates and a safe consulting 
engineer. 



USE. 



339 



Mr. Edward A. Rix is better known on the Pacific coast than in the east. 
He has been intimately connected with compressed aii: during most of his 
business life. Mr. Rix is versatile and clever. As an inventor he has produced 
Ihe Rix Drill and Air Compressor; his best work, perhaps, being the air plant 




FIG. 109. — EDW^ARD A. RIX. 

designed by him for the North Star Mining Company, Grass Valley, California. 
Mr. Rix has made some interesting and useful contributions to compressed air 
literature, among them "Rix Engineering Pocket Book," and several magazine 
Jirlicles. 

Mr. Henry C. Sergeant is well known in connection with The Ingersoll- 
Sergeant Drill Co. Among his inventions are the Ingersoll Eclipse and the 




FIG. 110. — HENRY c. sei«;eant. 



Sergeant Drills, the Sergeant Coal Cutter and the liigersoll-Sergcant Air Com 
I pressors. He first attracted attention in 1861, when by Act of Congress the United 

States Government gave him $10,000 for a marine engine regulator. He was at 
■ that time twenty-six years of age. All his inventions have been in the line of 



340 



USE. 



steam, gas and air machinery. The Patent office records bear evidences of Mr. 
Sergeant's fertility as an inventor. His work always bears the mark of practical 
simplicity, combined with economy of construction and operation. 

Mr. J. W. Thomas, Jr., is assistant general manager of the Nashville, Chat- 
tanooga & St. Louis Railway. He designed and has successfully applied an orig- 




FIG. III. — J. W. THOMAS, JR. 

inal pneumatic system of handling switches and signals, described in Vol. H., No. 
8, Compressed Air, and elsewhere in this book. 

Mr. Charles E. Tripler has recently attracted much attention in connection 
with liquid air. He has been engaged in researches in high pressures for the 




FIG. 112. 



:HAS. E. TRIP1.ER. 



liquefying of gases for a number of years, having devoted all his time and a great 
deal of money to this work. During his researches he devised a simple and 
economical apparatus for the liquefaction of gases, his investigations on this 
subject having developed many important results. 



USE. 34t 

SOME OF THE USES AND ADVANTAGES OF COMPRESSED AIR.* 

Previous to 1890, compressed air was used around railroad shops to a very 
limited extent. On roads having freight cars equipped with air brakes some of 
the freight repair yards were fitted with lines of pipe for testing the brakes on 
cars. For some time air had been used to force couplings into air brake hose and 
a few shops had air jacks for raising freight and passenger cars. The air pres- 
sure was supplied by locomotive air pumps and the limited amount of air fur- 
nished by each pump prevented a very general use of compressed air appliances, 
as it often required from six to eight air pumps to maintain the supply; more 
fuel was required in shops of ordinary size to furnish steam to run the pumps 




FIG. 113. — AIR-DRIVEN BREAST-DRILL. 

than was used to drive all the machinery in the shops. In machine shop practice 
the use of compressed air was confined to small pneumatic hoists. 

In 1891 its first application to car work was for cleaning the dust from 
window sashes and blinds in coaches and such parts of the inside as could not be 
reached with a feather duster, a round nozzle with a 3-32 inch opening being 
used. This led to the application of a flat nozzle for cleaning cushions and seat 
backs, and afterwards for cleaning carpets, bedding and blankets in Pullman 
cars. The Pullman Palace Car Company recognized its superiority over any 
other method of cleaning, and where it could be done, contracts were made pay- 
ing twenty-five cents for the air furnished to clean each sleeper. 

Air pumps not being able to meet the demand, an air compressor was added 
giving an increased supply, and a new field was opened for air power. Air lifts 
began to replace the chain blocks or different pulleys at all the heavy machines ; 
the driving wheel lathe being supplied with an altachnKMit to work in a horizontal 



* Read by J. H. McConnfill before Western R. R. Club. 



342 



USE. 



as well as a perpendicular direction to draw the wheels in or push them out from 
the centers. 

As it required a large number of these lifts in an ordinary railroad shop it 
was necessary to devise some economical way of making them. By taking or- 
dinary lap welded iron pipe cut to the required length and forcing a wrought iron 
die through, the pipe was made perfectly round and smooth inside and a leather 
packing on the bottom side of the piston made a tight piston when the air 
was applied, and allowed the piston to descend quickly when the air was 
released. A cast iron head was provided on each end and these were held in 
place with half inch or five-eights inch rods, A i% or a i^ inch piston rod was 
used with a hook and swivel on the end and an eye bolt screwed into the top 
cylinder head. These parts, together with an inlet and discharge valve, com- 
pleted the lift. Those which have been in service five years have been very satis- 
factory and it has not been found necessary to make any change from this method 
in its lifts raising ten thousand pounds. 

* The introduction of air into shop practice has brought out, in the last three 
or four years, a number of valuable and useful tools such as pneumatic drills, 




I Forged Stee/. 
FIG. 114. — PORTABLE PNEUMATIC RIVET DRIVER. 



pneumatic hammers, riveting machines for fire box, boiler and tank work, stay 
bolt cutters and stay bolt breakers. The pneumatic drill performs a very im- 
portant part in building a new boiler or putting a new fire box in an old boiler. 
Two men with two drills can tap out the holes and screw in seven hundred stay 
bolts in a fire box in fourteen hours. By the use of a simple tool attached to the 
end of the shaft of the drill, stay bolts are screwed into the fire box without a 
square shank being provided on the end of the bolt, thus avoiding the necessity 
of forging a square head by which to screw it in. This drill has entirely sup- 
planted the flexible shaft in work about locomotives, and in some shops a rachet 
is rarely seen in drilling holes about a locomotive boiler or frame. An air motor 
is considered an indispensable tool for flue work,' and the past three years have 
not seen a flue fastened in a locomotive boiler except by use of one of these tools. 
Applied to a cylinder boring bar it will run a good size cut through a cylinder; 
attached to a valve seat facing machine it does its work quickly and very satisfac- 
torily. It affords a quick and convenient way of grinding steam pipe rings. The 
pneumatic hammer has also come to stay. For chipping castings, caulking 



USE. 343 

boilers, beading flues and driving rivets, it is one of the most valuable pneumatic 
tools in service. The application of air to portable riveting machines has done 
away with a great deal of hand riveting. With the exception of one end of the 
connection sheet between the cylindrical part of the boiler and the fire box, a 
boiler can be entirely riveted by air machines. 

In car shop work air plays an important part. Jacks for passenger and 
freight car work are indispensable and any shop can have them if they can buy 
the castings. They are easily and cheaply made and can be built in any shop 
having a boring mill or a thirty-inch engine lathe. A small jack for raising 
draw heads, another for pulling down old draft timbers, do not cost much and 
they save time and labor in doing the work. Sand papering the surface of a 
passenger coach by an air machine makes better and is cheaper work than can 
be done by hand. On roads using gas in coaches an application of a jet of air 
and gas through a Bunsen burner removes the paint in a very quick and clean 
manner with no danger from fire. Attach a half-inch hose to the gas pipe in the 
car and another hose on the air supply, connect them both to the burner and see 
how cleanly and quickly you can burn ojff a coach. If you mix any paint, make a 
galvanized iron tank to hold fifty gallons— or make two if necessary — bend a 
piece of half-inch gas pipe in a circle two inches smaller than the inside of the 
tank, drill about fifteen holes on the top side of the pipe, plug up one end, put 
an elbow on the other, screw in a piece of half-inch pipe about four feet long, 
put on a globe valve, couple on the air, fill the tank with lead and oil or paste 
and oil, turn on a small quantity of air and see how quickly it will mix it. The 
material becomes agitated as if it was boiling. It is superior to any other way of 
mixing paint and it runs itself. 

The use of air for painting buildings and freight cars has been success- 
fully carried on for the past three years. Applied to a machine for white-washing 
it will cover a great amount of space; a twenty stall round house can be white- 
washed in twenty hours. I have seen a mai:hine shop 150x200 feet with a trussed 
roof white-washed, over the walls, the roof and the trusses, in ten hours. For 
crossings, fences and bridges, it is the cheapest and quickest way; it makes a 
smooth surface and drives the white-wash into places which a brush will not 
reach. 

In our machine shops air is now as important as steam. It is performing 
many things better than steam did, as there are many tools about a shop run by 
air that could not be run by steam. A three cylinder brotherhood engine operated 
by air is one of the most important tools in the shop. It is r^ounted on a small 
iron truck and can be readily moved. All complete it does not weigh over two 
hundred pounds. It will run an 18 inch slotter, a 42x42 inch planer; it will run 
a small driving wheel lathe and turn tires up to 56 inches in diameter; it will 
run a lathe for turning steel tired car wheels ; it will run a drill press, a bolt cut- 
ter or any single machine, and frequently it will save running the whole shop 
when it is necessary to run one machine only. A press for rod work, driving box 
brasses, or other work that does not require over 15,000 pounds on the piston is a 
great improvement over the old screw press and much quicker. 

An emery wheel driven by air on the principle of the Pelton water wheel 
makes a very handy tool for light grinding, two six-inch emery wheels on one 



344 USE. 

shaft can be run from a quarter-inch pipe. A transfer table of one hundred feet 
travel can be successfully run by air by using a small engine. 

Among the many uses of air in our shops that of blowing out steam pas- 
sages in cylinders commends itself at once. To do this, fill the boiler with air 
at 100 pounds pressure, blow out the ports, put in the pistons, fill the boiler again 
with air and run the engine out of the shop into the round house. You have 
burned no wood, nobody has waited for the engine to get hot, and you have saved 
several hours in time in finishing the engine. In testing stay bolts with lOO 
pounds of air pressure on the boiler, a broken stay bolt is immediately detected 
when sounded with a hammer, when it might not be discovered if sounded when 
the boiler was empty or full of water. 

At the scrap pile a cheap and effective shear for cutting off bolts to length 
can be made by using two short pieces of sixteen inch "I" beam and a passenger 
car brake cylinder which can be made to work automatically or by hand. A 
freight brake cylinder set in an upright wooden frame with an anvil below and a 
steel head on the end of the piston rod makes a good automatic hammer for 
straightening bolts and rods. The valve motion to the hammer consists of an 
ordinary three-way cock with a lever attached to the plug and a half-inch rod 




FIG. 115. — PNEUMATIC TRACK-SAXDER. 

connection to the end of the piston rod. The supply of air regulates the stroke. 
It can be regulated as closely as a steel hammer and will strike two hundred 
blows a minute if desired. These tools can be located anywhere about a yard. 

A sixteen inch cylinder makes a press for the tin shop, and with the proper 
dies and stamps the largest part of your tinware can be cut out, stamped and 
flanged ready to be put together. Galvanized iron water pails, dope and other 
buckets, are made in this way in pieces. The sides are cut out in sections, two 
sections forming the pail. The bottom is cut out and flanged at one blow. The 
tops and bottoms of tin or galvanized oil cans are made this way; also engine 
oilers, oil cans, spouts, tallow pots, water glass lamps, and a great variety of tin- 
ware can be made more cheaply and quickly than by hand. 

Attach a small air cylinder to the splitting shears in the sheet iron shop 
and you have a very effective shear for splitting sheets from three-sixteenths of 
an inch in thickness down. 

A portable forge for rivet heating and light blacksmith work is made by 
using a three inch iron tube below the fire plate. Extend this down below the 
bottom of the forge, connect a quarter inch gas pipe, use an elbow on the pipe, 
screw in a brass nipple with a 1-32 inch hole for the discharge, place the top of the 



USE. 345 

nipple there ^-inch above the bottom and in the center of the tube and use a 
quarter-inch globe valve to regulate the supply of air. With this forge rivets can 
be heated faster than two gangs can drive them, and a welding heat can be made 
on a bar of two and one-half inch round iron. 

In the office attach an eight inch cylinder to the letter press for copying 
letters ; you will like it so well that you will not want any more screw letter 
presses. 

The application of air in a sand house as a means of elevating sand to a 
tower where it can be discharged through a spout into the sand box of the loco- 
motive has been adopted on a number of railroads. A passenger car auxiliary 
reservoir with the necessary air connections makes a convenient and economical 
machine for kindling fires in locomotives with oil. In a blacksmith shop a blast 
for all fires can be supplied by compressed air and the fan blast dispensed with, 
experiments in this direction having demonstrated the success of this plan. 

New applications of air are constantly being made about railroad shops, 
each new application suggests another, and no shop is complete at the present 




FIG. Il6. — AIR DRILL AND REAMER. 



time without an air compressor. Even small shops can afford to dispense with 
locomotive air pumps and buy a compressor, because one that will furnish as 
much air as six pumps can be purchased for about $800. 

The economies effected by the use of air will, in a short time, pay for a 
complete air plant. A large reservoir supply is a great advantage, the larger 
you have it the more economically can the system be operated. A machine shop 
to-day can be fitted up to a better advantage and for less money than ever be- 
fore. No main line shafting extending the entire length of the shop is neces- 
sary. A short line shaft may be used for heavy machinery and all the light ma- 
chinery may be driven by air. 

Th« last five years have produced many useful compressed air tools and 
the future will bring out others. Manufacturing establishments are investigating 
the advantages of air, and all railroad shops are more or less engaged in bringing 
out new appliances so that we are looking to the future and wondering what will 
be the next application of compressed air in shop practice. 



346 USE. 

ECONOMIES EFFECTED BY COMPRESSED AIR. 

In an article by C. W. Shields, published in the Raihvay Age, Mr. J. H. 
McConnell, Siip't, M. P. Union Pacific R. R., is credited with furnishing the fol- 
lowing summary of time and expense saving in various shop practices when 
done by compressed air: 

Saving 
per day. 
Putting wheels in wheel lathe, three lathes in the shop an average of one 

change a day, save one man in handling this work $i 60 

Hoisting steel-tired wheels and axles in lathe, average of six changes a day, 

save one hour in time, $1.60; and one man less to handle the work, .20. . i 80 
Hoisting axles into cut-off lathe, an average of ten changes a day, save one 

hour per day in time 25 

One large boring mill averages two changes a day, $1.60; saving of time of 

30 minutes and the use of one helper, .15 i 85 

Handling cylinders in large boring mill and planer, save the labor of one 

man and one-half hour each change i 60 

Three men working on pistons, etc., in raising them from the floor to the 

bench, serving three machinists, save one helper five hours a day 80 

Raising chucks, face plates, and other heavy work, air hoists in the ma- 
chine shop save one helper one day i 50 

Lifting driving wheels and other heavy work on the large slotting machine, 

save the time of one man and 20 minutes i 50 

In applying cylinders on boilers, save one machinist and helper's time of 

10 hours 2 40 

Facing valves, save helper's time of four hours 60 

Pressing on driving wheels and axles, etc., three less helpers one hour each. .45 

Boring out cylinders, three helpers' time four hours i 80 

Applying driving brakes to old engines, drilling holes, reaming, etc., saving 

15 hours of time of machinist and helper 6 70 

Pneumatic tin and galvanized iron press, in getting out stock for 20 dozen 
water buckets, get it out in eight hours where it previously took 40 hours. 

In making brake shoes stam.ping a loup to have a casting run on, pre- 
viously one man would do 200 in a day where he now does 600. All work on 
this machine saves in the neighborhood of from 50 to 60 per cent. 

Running foundry elevator with the air hoist saves 25 per cent, of one 
man's time. 

Save 75 per cent, time putting in stay bolts in a fire box by using air 
motor for tapping out holes and screwing in bolts. 



iMiik 



USE. 347 

Save in the neighborhood of 50 per cent, in using pneumatic hammer for 
caulking both flues and boilers. 

Take engines in and out of roundhouse when necessary to change them, 
saves the work of six men pinching possibly 45 minutes, not counting the delay 
of the men waiting to go back to work on the engine. 

Blowing out engines with air, save a cord of wood, besides the incon- 
venience and delay, as the men cannot work around a hot engine to advantage. 

Handle all engines on the transfer table now run by air, previously run by 
crank. One man does now what six did before ; where six men move a foot 
in a minute, air motor under like conditions will move twelve feet. As this is 
moved several times a day, this in itself is a great saving. 

Pneumatic hoist for unloading scrap at the foundry, the old method took 
six men 10 hours; under the same conditions with the hoist, two men will do it 
in 4 hours. 

Unloading a car of wheels, it takes six men half an hour; now three men 
will do it in 15 minutes. 

Sandpapering ofif a 50-foot baggage car by hand took in the neighborhood 
of 60 hours ; now it takes 14 hours with the sandpapering machine. 

Air jacks for raising and lowering freight cars now take one man three 
minutes where previously it took two men ten minutes. 

Truck jacks to remove three pairs of wheels takes ij^ hours; the old 
method takes 6 hours. 

Cleaning a car save about 10 per cent, in time and 90 per cent, thor- 
oughness. 

Air whitewashing machine, where it took ten men five days it now takes 
four men one day, and a 75 per cent, better job. 



DONTS! FOR USERS OF COMPRESSED AIR. 

The following hints have been drawn up in a somewhat breezy American 
style : 

Don't install a compressor just about equal in capacity to your present re- 
quirements, for when Dnce you have compressed air available, its number of uses 
becomes legion. Good practice is to provide a compressor at least fifty per cent, 
greater in capacity than your immediate necessities demand. Duplex compressors 
are made devisable, permitting the installation and operation of one-half at first 
and the other half later, when the additional capacity is needed. 

Don't accept the theoretical capacity of an air compressor, stated in the list of 
the maker, as the equivalent of the actual volume of air needed for your service. 
Remembering the difference blwecn theory and practice, allow a small deduction 



348 USE. 

for friction, heat, clearance, etc., being unavoidable losses in air compression, 
before calculating what your actual delivery in compressed air will be. 

Don't buy an air compressor because it is cheap. It will prove the most ex- 
pensive proposition of its size that you have ever encountered. If a water pump 
fails in its work, you will know it at once; if a steam engine is deficient, its short- 
comings are self-evident; but if an air compressor is poorly designed or badly 
constructed, it may continue in the evil of its ways until the scrap heap claims it 
for its own, unless, as is more than likely, an absolute breakdown calls attention 
to its deficiencies, and you learn all too late that the hole it has made in your coal 
pile, added to the loss of keeping it in repair, would have paid a handsome interest 
on the additional first cost of a properly designed and properly constructed com- 
pressor. 

Don't buy a second-hand compressor unless you know it has given satisfac- 
tion in work similar to your own, and that its working parts retain their full 
measure of usefulness without deterioration. An air compressor with valves, 
pistons, etc., worn out or in bad repair can waste more good power than anything 
of its size known. 

Don't buy a compressor that your neighbor used for operating oil burners 
because you intend putting in pneumatic tools. For, even if all compressors look 
alike to you, experience teaches that oil burners operate under 12 pounds pres- 
sure, whilst pneumatic tools require 100 pounds, and the oil-burner compressor, 
with unevenly proportioned cylinders, devoid of water jackets, will equal your 
service as well as a low-pressure boiler for heating will run a high-speed engine. 

Don't use air-break pumps or direct-acting compressors. Statistics show that 
their steam consumption is about five times that of a crank and fly-wheel com- 
pressor for the same volume and pressure of air delivered. 

Don't install a steam-driven compressor if your steam supply is short and 
plenty of belt-power available. 

Don't put in a belt-driven compressor if you have plenty of steam and are 
short of belt power. 

Don't purchase a compressor of out-of-date design because you have heard 
of it for many years. Noah set the fashion in arks, and is known throughout 
civilization, but modern house-boats have evidenced the progress of the times by 
departing materially from Noah's standard. 

Don't draw your intake air to the compressor from a hot engine-room, or 
from any point where dust is abundant. The volume of air delivered by the 
compressor increases proportionately as the temperature of the intake air is low- 
ered, and dust or grit entering the compressor clogs the valves, cuts the cylinders, 
and generally impairs the efficiency. 

Don't use any old thing for an air receiver. Compressed air under 100 lbs. 
pressure will leak a horse-power through a 1-16 diameter hole in five minutes, 
and a well-made, strong and tight air receiver is the second essentially important 
factor if you would realize to the utmost all the advantages which compressed 
air provides. 



USE. 349 

Don't connect your air admission and discharge pipes improperly at the re- 
ceiver. To secure the best results and eliminate moisture from the compressed 
air, connect your pipe leading from the compressor at the top of the receiver and 
lead your air pipe to points of consumption from the bottom of the receiver. 

Don't have leaky air pipes. Test your piping when it is installed and at 
regular intervals thereafter, allov^^ing the full pressure to remain an adequate 
length of time, and if the gauge indicates leakage, locate and remedy it. 

Don't install your piping without properly providing for drainage of con- 
densed moisture at regular intervals in the system. The simplest method is to 
slightly incline the branches leading from the main line and insert drain cocks 
just before the hose connection is reached. — New Zealand Mining and Engineer- 
ing Journal. 



PROGRESS IN COMPRESSED AIR. 

Mr. Walter H. Knight, consulting engineer of the American Air Power Co., 
the International Power Co. and the New York Auto-Truck Co., in discussing 
the advance to a practical point of compressed air for use as a motive power, says : 

"The recent advances made in structural material has enabled us to handle 
pressures with absolute safety that were not heretofore possible. These air pres- 
sures mean a greater mileage of vehicles, so that, where one of the old time 
vehicles, such, for instance, as the compressed air cars used in Paris, can make 
but two or three miles from one charge, we are now able to run from 25 to 50 
miles without recharging. We can build air cars to-day that will run half a day 
on one charge, having thus to be charged only at night and at noon. 

"The air flasks that hold the compressed air under several thousand pounds 
pressure have been rapidly evolved during the last few years, so that now we can 
produce in this country, without going abroad, nickel steel flasks, not only twice 
the strength of those formerly used, but which are absolutely incapable of ruptur- 
ing under the pressure used. 

"There is absolutely no more danger in connection with the pressures used 
than there was, for instance, with electric motors, where the centrifugal force en- 
genders a pressure of over 5,000 pounds per square inch in the armatures and 
commutators. This is evidenced sometimes by commutators distributing their 
commutator work on the roof of the car. In fact, the flasks are much safer, be- 
cause the pressure is always definite, and not dependent upon some variable factor 
like centrifugal force, speed, or as in the case of a steam engine, low water, hot 
fire sheets, etc. The air pressure is a cold pressure and can never exceed that 
which is given it by the compressor, which itself can go no higher than a certain 
point and is just as fixed and absolute as is the strain upon the cables of the 
Brooklyn Bridge. It is always in this, as in other cases, a question and factor of 
safety. The Brooklyn Bridge would be a very dangerous structure if the cables 
were not strong enough. If they are, it is safe. 

"Quite as important as the question of air reservoirs in bringing the air 
motor out of the impracticable into the practicable field was the question of heat- 
ing, which has now been improved to such a point by the use of hot water in con- 



350 USE. 

nection with the air, that more than double the effect is obtained from the same 
amount of heat as was done two years ago. This, together with the simplification 
of the motors to a point where tliey are scarcely more complicated than an air 
brake, enables us to produce an air vehicle that fulfills every requirement of an 
automobile. These vehicles may be charged instantaneously instead of requiring 
six hours, as in the case of a storage battery; their reservoirs are of unlimited 
durability instead of being susceptible to the rapid depreciation that affects the 
storage battery. They have only one-half the weight of a storage battery and, in 
common with the latter, possess an entire freedom from any aesthetic objection, 
such as exhaust, odor or noise. 

"Analysis shows that only the stored powers are suitable for automobile 
work in cities. All prime powers have some one or more radical objections from 
an aesthetic or practical standpoint. Thus the gasoline or gas motors, when you 
come to have vehicles of any size, have a very objectionable odor. Even the 
smaller ones are disagreeable enough. Moreover, vehicles of this type lie down 
and die when they come to grades, even worse than do the storage battery ones, 
whereas air motors can be used on grades as steep as 20 per cent. 

"There is no danger of injuring the reservoir by a sudden draught upon its 
power, nor is there any injury accompanying the total exhaustion of the reservoir. 
For street cars, it does away with all appliances along the line, such as trolley 
wires, underground connections, cables, etc., and requires only a good roadbed. 
For long distance work, such as now handled by steam locomotives, it offers on 
the one hand a stored power not limited by fire box or heating surface, and not 
requiring dangerous, inconvenient and expensive third rails or trolleys. It fur- 
ther offers an economy much superior to that of the steam locomotives, on ac- 
count of drawing its power from a stationary engine, which, as is well known, 
produces power for about one-sixth the cost of that produced by a steam 
locomotive. 

"We are in the jiir business at the birth of a gigantic industry (as we were 
fifteen years ago in the electric business), that will reach out into every field of 
power and bring about economies and simplifications that the much-vaunted 
electricity is incapable of realizing. 

"For truck work, where tremendous power is required, with minimum 
weight and absolute reliability, there is no other force that I can see that comes 
anywhere near it. Our tracks for carrying 20,000 pounds weigh only 8.000 
pounds. They are made of steel only and are as durable pieces of mechanism as 
any that I know of. They can run at an expense not exceeding ^c. a mile for 
power, and with instantaneous charging at numerous substations can cover any 
desired distance. Even with one charge, they can make an ordinary trip in the 
Metropolitan district with a maximum load." — Raihvay Era. 



COMPRESSED AIR SUBSTITUTED FOR STEAM. 

A recent instance of the economy resulting in certain cases, from the sub- 
stitution of compressed air for steam is found in the Paraffine and Lubricating 
Department of the extensive refining plant of the Tide Water Oil Company at 



USE. 



351 



Bayonne, New Jersey. In this plant the air from the compressor goes to a suitable 
tank or reservoir, thence to a series of direct acting steam pumps first reheated as 
shown in Fig. 117 — thence through second reheater to second series of pumps, 
which .were formerly actuated by steam, the exhaust air being finally utilized in the 
bleachers. The equipment not only performs the essential work formerly done by 
steam, but the compressed air system also does away with the use of several 
small compressors which supplied air to two pressing plants, the wax refinery and 




-REHEATING AT I'UMTS. 



also to the acid works. The machinery was furnished by the Ingersoll-Sergeant 
Drill Company, of 26 Cortlandt Street, New York, and Mr. P. R. Gray, Superin- 
tendent, of the oil works designed and put in the system. 

From the compressor the air is conducted into an old stt-ani cjruiii which 
was formerly attached to the No. 2 battery of boilers, and from this drum, which 
serves as an air storage tank, the main line leads to the several oil agitators, 
with branches at several intermediate points for supplying the pumps with 



352 



USE. 




Wifm ' I J ■lyw'i-ff^'.i -ri^^' ■'^ ■ '»^'^- 



USE. 



353 



where . leam was used heretofore. Heaters for reheating the air for power 
f^ere arranged in connection with the pumps, and the piping was so placed that 
the air after being twice used as power was finally used, as stated, for clearing the 
oil in the bleachers. The large pipe and fittings formerly employed for blowing 
the agitators were all replaced by smaller sizes in more simple arrangement. The 
larger portion of the air is used in blowing the agitators for which purpose three 
large steam blowing engines were used before. One portion of the pumping plant 
is illustrated in Fig. ii8. These pumps are of the Smith Vaile duplex type, and are 




FIG. 119. — STORAGE TANK. 



arranged in two groups in the same compartment. The total number of pumps is 
14, 12 of which are placed in the building shown in Fig. 117. Six of these have 
steam cylinders 7 inches in diameter, pump cylinders 6 inches in diameter by a 
stroke of 9 inches; one pump haying steam cylinder 12 inches, pump cylinder 6 
inches by a stroke of 11 inches; four pumps, steam cylinder 5 inches, pump cylin- 
der 4 inches, and a stroke of 8 inches; and one pump steam cylinder 6 inches, 
pump cylinder 6 inches by 6-inch stroke. Air for the first series of pumps is first 
reheated in the reheater shown in Fig. 117, the air being used at a pressure of 60 
pounds, and exhausted against a back pressure of 30 pounds. The exhaust is 
again reheated and passed to the second series of pumps which are designed for 



354 



USE. 



lighter service where it is exhausted against a pressure of 7 pounds into a storage 
drum, Fig. 119, from which it passes to the bleachers. This third use of the air 
was not included in the scheme as at first mapped out. The system is so adjusted 
that if the work being done at any time by the light service pumps does not use 
all the exhaust air from the high pressure pumps the surplus may be passed to the 
agitators for blowing. 

In a statement made by Mr. Gray to the directors, we find the following: 
"This plant has displaced three steam blowers which used, when running in ag- 




FIG. 120. — REHEATING FOR ACID WORKS AND PRESSING PLANTS. 



gregate, at the rate of 239 horse power of steam, average time run eight hours in 
24, or net average, 79 boiler horse power. Also two air compressors, 34 horse 
power; also steam displaced in 14 pumps which before used every 24 hours 90 
boiler horse power, making total boiler horse power of steam displaced by air at 
the agitators, 203. Add three smaller compressors at the pressing plant and wax 
refinery, using an aggregate 30 horse power, makes a total of 233 horse power. 
Deduct from this the average of 55 horse power used by the Payne engine to 
drive the compressor makes a saving of 178 boiler horse power or $4,450 per 
year." 



USE. 355 

The plant was started in January 28, 1897, and with a few exceptions has 
been in use ever since, has run without a hitch or drawback, and does all that was 
expected of it by the company. 



COMPRESSED AIR AS USED EOR POWER PURPOSES. 



DELIVERED BEFORE THE ENGINEERING SOCIETY OF COLUMBIA COLLEGE, ON APRIL 22D, 
1896, BY FREDERICK C. WEBER, M. E. 



" Professor Hutton and members of the Engineering Society: The subject 

outlined for the lecture to-day is "Compressed Air for Power Purposes." 

The use of compressed air as a motive power presents many an interesting 
problem to the engineer, and especially at the present time when almost daily 
some new use is discovered for compressed air, so that the list of uses to which it 
is successfully applied is getting so large that it is difficult to keep track of them all. 

A slight acquaintance with this power soon convinces one that it is now 
rapidly asserting its claim to being the one pozver that can be most generally ap- 
plied. Only a few years ago it was restricted to the mine, the tunnel, and for 
work in confined spaces, and since it .was the only power that met the essential 
requirements of these places, the question of economical production and use did 
not enter very largely into consideration, so that the early compressors were ma- 
chines of very low efficiency compared with the best compressors of to-day. 

As soon as uses were found for compressed air, that made economical pro- 
duction an important factor, the compressor began to improve; the improvement 
has" been slow, however, and this subject still offers a big field for investigation. 
The indicator, which has done so much for the development of the steam engine, 
seems to have been applied very little at the air compressor, and it is only re- 
cently that manufacturers began to take cards from their own compressors. 

To understand this subject of air compression in all of its details,, some 
acquaintance with the science of Thermodynamics is necessary, and it seems that 
an air compressor would not be out of place in a laboratory of an Engineering 
College, where the heating and cooling effects of the air can be studied; also 
the question of the jacket and intercooler. The exact si^e of the latter has not 
been determined as yet; also the transfer of heat units from air to water through 
different media. Intelligent investigation would still reveal much to the manu- 
facturer that is unknown to him, and would help to bring the air compressor and 
air motor upon the same high plane of the steam engine. This has reference 
especially to compound compressors, the economy of which over the simple com- 
pressor is not doubted and about which much remains that is unknown. 

LITERATURE. 

Literature upon this suljjcct is not very extensive; it involves the science 
of Thermodynamics, and is also intensely practical, so that in order to advance 
in it a knowledge of the practical and theoretical is necessary. 

Professors Wood and Peabody, in their works on Thermodynamics, give 
considerable space to air compression, the air compressor, and air motor. A. von 



356 USE. 

Ihering, in "Die Geblaese," published in Berlin by Julius Springer, 1893, treats the 
subject very exhaustively, and his work is really the highest authority to-day on 
air compression. 

Quite a number of articles on compressed air and air machinery in general 
have appeared from time to time in the various technical journals, chief among 
them the American Machinist and Scientific American. Within the past month 
a paper called "Compressed Air" has made its appearance; it is devoted princi- 
pally to the subject of air compression, and contains both theoretical and practical 
considerations on this subject. 

PRINCIPAL USES. 

Chief among the uses to which compressed air is applied, may be men- 
tioned : 

Driving rock drills. 
Operating air hoists. 

moulding machines, 
sand blast, 
chipping castings, 
air brakes. 
For cleaning car seats. 

switch and signal service, 
the Pohle air lift pump, 
sinking caissons, 
caulking. 
Operating motors. 

street cars. 
A complete list of uses up to date will be found in a work on compressed 
air by Frank Richards, published by John Wiley & Sons, 1895. 

Its use in the mine and tunnel is probably as yet the most general, owing 
to the peculiarity and confined nature of this work, and other considerations, both 
mechanical and economical, which exclude steam, water and electricity. 

Soon, however, some of the many other uses to which it is applied will 
equal in importance its use in the mine. 

RAILWAY. 

The railway companies all over the country recognize its importance in the 
safe handling of trains under very high speeds, and its position in the railroad 
shop and foundry will be hard to replace with any other power. 

POHLE PUMP. 

The Pohle pump is a valveless pump ; the air under pressure is liberated at 
the bottom of a well, and by virtue of its expansive force, it raises a column of 
water from a depth at which the ordinary piston pump fails. 

Sometimes a piston pump is placed so far from the steam-boiler that con- 
densation losses in the pipes and heat generated when the pump is working in a 
confined space, give compressed air the advantage in operating this style of pump. 

TRAMWAY. 

Another important use is its use on the tramway, or in operating street 
car motors. I propose to deal somewhat at length upon this particular use; an<J 



USE. 357 

since its application here involves high pressures, the compound compressor will 
receive a greater share of attention at the end of this article, and I will restrict- 
myself to the use of high pressures as applied in the Hardie motor, having with 
others made an exhaustive test on this motor in May, 1895. 

PRODUCTION. 

Physical Properties of Air: 

Air is considered a perfect gas, and is therefore subject to the natural laws 
affecting perfect gases. 

WEIGHT. 

The weight of one cubic foot of dry air at temperature of melting ice and 
at barometric pressure of sea level (29.92 inches mercury), is .080728 lbs. (M. 
Regnault.) 

VOLUME. 

The volume varies inversely as the density; or, 

I 
V=T^=i2.387 cubic feet per lb. (at sea level and at temp, of melting ice). 

PRESSURE AND TEMPERATURE. 

Under constant pressure its volume varies directly as the absolute tem- 
perature. 

For constant volume the pressure is proportional directly to an increase in 
temperature, when expressed algebraically — 

(V,)pOcT) 

(PA)v«^Tf • ^• 

or by combining Boyle's law with that of Gay Lussac — 

~T^ = ^f^ = ^ "• 

Po= Atmospheric pressure at sea level. 

To = Temperature (absolute) of melting ice. 

Vo=Volume of one pound at that temperature (Tq) and pressure (Pq), and is a 

function of the density. 
?! Vi Tj are specific values 
C=53.2i for air. 

SPECIFIC HEAT. 

Air has two specific heats, one at constant pressure 2375 

the other at constant volume 1689 

^, ^. .Cp .2375 

The ratio of ^^ = n = y^g^ = 1.4061 

GENERAL PRINCIPLES OF COMPRESSING. 

Work of Compression : 

(Simple compressor.) 



358 USE. 

W=Pi Vi logE^B— foot pounds (isothermal) III. 






Wi=Pi Vi ___ __ _ 

foot pounds (adiabatic). . . IV, 



when Vi=: volume of one pound of air at the pressure Pj and compressed from Pj_ 
toPg. 

COMPOUND COMPRESSORS. 

w,=p, V, ii:z:T|_lpJ "-hipj !L. J V 

when compression is done in two stages and cooled to atmospheric temperature 
between stages. 

P 2= Intermediate pressure, and work done is a minimum when 
P =V P^ P3. 

COMPRESSION. 

The first law of Thermodynamics tells us that heat and mechanical energy 
are mutually convertible; therefore, when the piston of the compressor is made 
to do work, heat is produced in exact proportion to the amount of work done 
(in the ratio of one B. T. U.) for every 778 ft. pounds expended. 

Since, however, the usual conditions under which compressed air is em- 
ployed place the motor at some distance from the compressor, this heat of com- 
pression is soon dissipated to the surrounding media, and this loss of heat then 
represents lost work, so that it is very desirable to be able to compress the air with 
aL little increase in temperature as possible. 

If the temperature could be kept constant throughout the compression, this 
process would be called an isothermal or equal temperature process, and if no heat 
passed to or from the air during compression it would be termed an adiabatic 
process. 

The loss due to the heat of compression is the greatest loss in the produc- 
tion of compressed air, and to prevent this loss a cooling medium is supplied that 
will abstract the heat during compression. Water is usually employed, and it has 
been used in various ways, calling into existence two distinct classes of com- 
pressors — 

i) Wet compressors. 

2) Dry compressors. 

In the first class water is introduced directly into the cylinder during the 
compression process, and in the second class no water is admitted to the air dur- 
ing compression. 

Wet compressors are subdivided into two classes — 

a) Compressors in which water is sprayed into the cylinder during com- 
pression, and 

b) Those which use a water piston for compressing. 

The first class of wet compressors has shown the highest degree of effi- 
ciency for one stage (or simple) compressors, because the water is thoroughly 



USE. 359 

mixed with the heated air and takes up the heat readily (due to the difference 
in the specific heats of water and air). The injected water must not be excessive, 
or damage will result to the compressor. An increased capacity also results from 
using water in the cylinder to fill the clearance spaces. 

Although the spray injection compressor will show a higher thermo- 
dynamic efficiency than the dry or jacketed compressor, its commercial efficiency is 
not so high, for water in the cylinder prevents proper lubrication ; impurities in the 
water also attack the walls of the cylinder, and the moisture in the air causes 




FIG. 121. 

freezing of the delivery pipe in cold weather, also choking of exhaust in motor 
due to freezing, resulting from low temperatures of expansion. 

The hydraulic piston or plunger compressor has a very low efficiency, and 
is now obsolete. 

In the Dry Compressor the external walls of the cylinder are flooded with 
water, the cooling effect is not as great as in the spray injection compressor but it 
overcomes all of the disadvantages of the Wet Compressor — it is very popular 
in this country while the spray injection compressor seems to be the popular 
compressor abroad. 

Fig. 121 shows the jacket (J) applied 'both on head and sides of a cylinder 
of the Ingersoll-Sergeant Compressor. 

The air enters the cylinder through the hollow tail-rod (E) the inlet valves 
(G) being placed inside the piston. At the beginning of the stroke both inlet 
valves remain stationary, due to their own inertia and the piston moves towards 
the valve on the compressing side and away from the intake valve, about J4" is 
allowed between valve and seat, this is sufficient to admit a free inflow of air; 
there is no loss in vacuum due to late opening. On the compression side the pres- 
sure line begins to rise very close to the beginning of the stroke and increases 
until slightly in excess of the receiver pressure when the discharge valve (H) 



360 



USE. 



opens and the air is now forced into the receiver until the end of the stroke. The 
crank is now passing the center and for an instant the piston comes to a stop 
before it goes on its return stroke, during this operation the spring in the dis- 
charge valve combined with its weight forces the valve to its seat, cutting off all 
communication between receiver and cylinder— the air that remains in the clear- 
ance spaces expands back to atmospheric pressure and then admission for the 
return stroke begins and the same cycle is completed as described above. 

SOURCE OF LOSS. 

The Efficiency of an Air Compressor is often stated in terms of the me- 
chanical efficiency and the efficiency of compression, this is the truth but not the 
whole truth, for in every Compressor there are two losses which effect the ca- 
pacity or the amount of air delivered— the Urst of these losses is that due to the 







heat of the inlet valves by the friction of the air in passing into the cylinder — the 
ingoing air coming in contact with these hot valves expands and consequently 
a less weight of air is admitted per stroke. 

The second loss is that due to clearance; the air in the clearance spaces 
in expanding back to atmospheric pressure prevents admission at the beginning 
of the stroke. The efficiency of the "intake volume" can be taken into account 
when a compressor is designed for a given quantity of air delivered, by increas- 
ing the diameter a fraction of an inch. 

The third loss involves friction of the mechanism, and has been reduced 
to less than 10 per cent, in the best compressors, and should not exceed 15 per 
cent. 



USE. 



361 



The fourth loss is that due to the heat of compression, and is the most 
serious, and can be best shown by a diagram. 

Fig. 1 22 shows a theoretical card (no clearance) from an air cylinder. The 
admission takes place at (A), follows along (A B) ; (A B G H) represents 
work of the atmosphere on piston in suction stroke. When the compression is 
isothermal, the compression line is represented by (B D) and by (B C) when 
compression is adiabatic. (C D E) represents receiver pressure. The tempera- 
ture for adiabatic compression in this card is (450° F.) at the end of compres- 
sion ; and from C to E it is lowered, due to the cooling action of the jacket water 
to about 400° F. From this diagram it is apparent that the benefit resulting from 
the jacket is greatest up to the point of communication between the receiver and 
cylinder (C) ; for after the terminal pressure has been reached there is no 




b^"^ 



-f a- 



FIG. 123. 



further need for cooling unless it be that the cooling for this part of the stroke 
(C E) helps to keep the cylinder cool for the next charge. If it were possible 
to obtain isothermal compression, the temperature throughout the process would 
be 60° F., and the area BCD would represent work saved. 

In an actual diagram taken from a dry compressor, the line of compres- 
sion lies very close to the adiabatic, because only a small part of the charge comes 
in direct contact with the cold walls; and since air has a very low specific heat 
and low conductivity, the cold does not penetrate the main body. When cards 
taken from a dry compressor show a compression line close to the isothermal, 
the chances of leakage by the piston or valves are very great. 

From the fundamental equation of a perfect gas we are able to deduce the 
following : 



P T ) 

-~=-=r- \ (when volume remains constant). 
* 8 ■••« » 



VI. 



362 



USE. 



Any increase in the ratio of pressures means a corresponding increase in 
temperature; and from what has just been said about heat losses, it is very evi- 
dent that any increase in pressure will be followed by a decreased efficiency of 
the compressor unless some means are provided for abstracting the heat during 
compression, for the jacket water of the simple compressor has been shown to 
abstract very little heat, the actual compression curve lying closer to the adia- 
batic than the isothermal. 

This being the case, it clearly shows that the simple compressor is out 
of the question for high pressures when economy is looked for. The compound 
or stage compressor offers the best solution of this problem. 

Fig. 123 represents a theoretical card taken from a compound compressor. 
The pressures are usually so proportioned that the total work is divided equally 




WATER INLET 



FIG. 124. 

between the cylinders. Since any increase in temperature depends upon the 
ratio of pressures, the advantage of the compound compressors is apparent. The 
temperature now at the end of compression in each cylinder is 240° F. The 
pressure in the first cylinder is carried to 41 pounds (absolute,) and in the second 
cylinder the pressure reaches 115 pounds (absolute). 

The line (L I F) represents the receiver pressure or the intercooler. The 
air in passing from low pressure to the high pressure cylinder, passes through 
an intercooler and is cooled down from 240° to 60° before it is compressed a 



USE. 363 

second time, or the shrinkage in volume is represented by I F. Compression in 
the high pressure cylinder begins at I, and for adiabatic compression follows 
along the line I H. Assuming, now, that the cylinder jackets are inefficient, or 
that the compression process has been adiabatic in both cylinders, the saving due 
to the intercooler will be represented by the area F I H C. 

INTERCOOLER. 

The air in passing from the low pressure cylinder to the high pressure 
cylinder is conducted through an intercooler, which acts at the same time as a 
receiver. 

This intercooler (Fig. 124) is filled with a number of small tubes made 
of material of high conductive capacity, through which water passes quite freely, 
and these tubes are so arranged that the air in entering the intercooler is made 
to flow over the tubes in fine layers, thus bringing as much of the whole body 
of air in contact with this cool surface as possible. 

It is quite necessary that the intercooler should be of sufficient size to pre- 
vent fall in pressure when communication is established between it and the high 
pressure cylinder. Another advantage of size will be the greater chance of perfect 
cooling, shown on the card by a decrease in volume at the end of compression in 
the first cylinder and the beginning of compression in the second. 

ACTUAL CARDS. 

A set of cards taken from a compressor will show many defects, some of 
which have been shown in the diagram of Fig. 123. For instance, if the admis- 
sion is not free, the compressor will be working against a partial vacuum, follow- 
ing along M O instead of N B. Then, if the jacket is inefficient, the compres- 
sion line will almost coincide with the adiabatic. Next, if the intercooler fails 
to cool the air to atmospheric pressure, the compression will begin at (K) in- 
stead of (I) in the highest pressure cylinder. 

The next loss is usually due to insufficient port opening at the discharge, 
or a loss in raising the delivery valve (P). If this valve is worked through a 
mechanical device from some other part of the compressor, a loss is often the 
result, due to late opening, the pressure in the cylinder being in excess of the 
receiver pressure, causing the air to expand from high pressure in cylinder to 
pressure in receiver, and no benefit is derived for the extra work done. Defec- 
tive closing of discharge valves also cause a loss, as will be seen at (R). Clear- 
ance losses have been shown to affect capacity only; however, in the compound 
compressor this loss is reduced to a minimum, for the air in the low pressure 
cylinder is at a lower tension, and consequently its expansion is not so great. 
The effect of clearance in the high pressure cylinder is to throw only a slight 
amount of extra work upon the low pressure cylinder. 

If the intake valve does not open at the proper moment, a partial vacuum 
results, causing another loss, due to negative work, as seen at N M. 

Fig. 125 shows a cross-section of a double compound Norwalk compressor, 
with intercooler. There are 4 cylinders — 2 air and 2 steam, arranged tandem — 
both pairs compounded. The cooling water is admitted first to the high pressure 
cylinder, then to the low pressure cylinder jacket, and lastly to the intercooler. 



364 



USE. 



The air is admitted to the cylinder by valves of the Corliss type, and have a posi- 
tive movement from the main shaft. 

THREE AND FOUR STAGES. 

The advantage of the compound compressor is very evident from Fig. 123, 
showing clearly how near we approach the isothermal line. Theoretically we 
can achieve isothermal compression only if we had an infinite number of stages 
to compress to. However, the friction of the mechanism will soon put a limit 
upon the number of stages. 

TABLE SHOWING PER CENT. OF WORK LOST. 

I have prepared a table (Table 39) showing the per cent, of work lost due 
to heat of compression, based upon Formula III., IV. and V. It is assumed 
that the temperature is brought back to atmospheric temperature between each 
stage, and no account is taken of the jacket cooling. 

These figures speak for themselves, and show the advantage of com- 
pounding very clearly. For instance, at 2,000 pounds pressure, the loss in one 




FIG. 12: 



stage compressor is 54.8 per cent. ; in a two stage, 30.8 per cent. ; and in a four 
stage compressor only 16.65 per cent. 



COST OF COMPRESSING. 

The cost of compression will be in direct proportion to the amount of 
work done — i. e., pressure and volume swept through — and will depend upon the 
style of compressor. If a slide valve compressor is used to do the work, 30 or 40 
pounds of steam may be counted upon to furnish a horse power; but if the com- 
pressor is a Corliss Compound Condensing Compressor, a horse power will be 
developed upon 15 to 18 pounds of steam, showing that for a permanent plant 
first cost is not the most important consideration. 



USE. 365 

TABLE 39. — PER CENT. OF WORK LOST DUE TO HEAT OF COMPRESSION. 





ISOTHERMAL COMPRESSION AS BASE LINE. 




One Stage. 


Two Stage. 


Three Stage. 


Four Stage. 




No account taken of Jacket Cooling. 


V JJ 




Air assumed to be cooled to atmos 


So 3 


n = 1.408 


temperature between stages. 


^S 










Per cent. 


Per cent. 




Per cent. 


60 


23 


11.8 




■ 4.45 


80 


25.26 


13.12 




4.80 


100 


27.58 


14.62 




7.41 


200 


34.40 


18.88 




8.27 


400 


40.75 


22.90 




11.04 


eoo 


44.6 


24.60 




13 10 


800 


47.4 


26.33 




14.32 


1,000 


49.2 


28.10 




14.45 


i,'.aoo 


51.6 


28.60 




14.85 


1,400 


52.0 


29.4 




15.00 


1,600 


53.3 


30.0 




15.54 


1,800 


54.0 


30.6 




16.05 


2,000 


54.8 


30.8 




16.65 



COST OF HIGH PRESSURES. 

II The power cost of compressing to high pressures is not proportional to 

I the pressure. It costs less proportionately to compress from 1,000 to 2,000 
pounds than it does to compress from atmospheric pressure to 1,000 pounds. 
This can be shown by placing proper values in Equations IV. and V. Theoreti- 

Ically a point can be reached in the compression curve where a slight increase of 
power will result in an infinite pressure. 

RAND FOUR STAGE COMPRESSOR. 



The total compression is accomplished in four stages, and it is designed 
especially for marine service, to supply the torpedo boat with power for discharg- 
ing torpedoes. 

The problem for the designer was compactness consistent with strength 
and least weight. 



INGERSOLL-SERGEANT FOUR STAGE COMPRESSOR. 

Fig. 127 represents a four stage compressor (witii intercoolcr) attached 
to a Corliss engine. The cylinders are single acting, and are fitted with plunger 
pistons. A compressor of this type will compress one cubic foot of free air per 
minute, from 15 pounds to 2,000 pounds per sq. in., at a power cost of .4-10 
horse power an\i 1.3 lbs. coal per 100 cubic feet of free air. There are three inter- 



366 



USE. 



coolers, each of sufficient size to reduce the temperature of the air at the end 
of compression to normal temperature. 



USE. 

Having thus shown how the air is compressed and by virtue of which 
energy is stored, our attention is next turned to the utilization of this stored 
energy. 

The air cylinders are all enclosed and surrounded by water. Three gauges 
are shown which record the pressures of the different cylinders. 



FIG. 




RAND HIGH PRESSURE COMPRESSOR. 



The intrinsic energy of one pound of air at atmospheric pressure and tem- 
perature of melting ice, may be shown to be by the following formula: 

^v To = ~Z? =64,735 foot pounds VIII. 

Cy =:Specific heat at constant volume. 

To = Absolute temperature of melting ice. 

Po =Mean pressure of atmosphere in pounds per sq. ft. 

Vq = Volume of i' at po and To, 

n =Ratio of specific heats = 1,406. 

Since the heat of compression due to the mechanical energy expended 
upon the air by the piston is usually dissipated to the surrounding objects be- 
fore the air reaches the motor, and for which we therefore get no mechanical 
equivalent, we are obliged to draw upon the intrinsic energy stored in the air if 
we wish to get any useful return for the work expended. 



HU^J^f^rV^r^*':^^' 



USE. 



367 



WEIGHT OF AIR USED. 

The number of cubic feet of free air used per minute for a given amount 
of work may be determined as follows: 



W 33,000 N 
^ — w = U w 



VIII. 



W=Weight of air per minute to deliver N horse powers per minute. 
w=Weight per cubic foot at atmospheric temperature. 
U=Work in foot pounds per pound of air. 








FIG. 127. — INGERSOIvL-SERGKANT FOUR STAGK COMPRESSOR. 

The value of U will depend upon complete or incomplete expansion, or 
upon full pressure working: 






IX. 



Pa = Initial pressure. 

V2 = Corresponding volume. 
^ Pa= Exhaust pressure. 
(No allowance for clearance, leakage and valve resistance.) 



368 USE. 

INGERSOLL-SERGEANT FOUR STAGE COMPRESSOR. 

From experiments made with reheating air at a point very close to its ap- 
plication, it has been found that U may be increased in proportion to the heat 
imparted, or in the ratio of — 

7p— (absolute temperature.) 

Since any increase in the valve of U will effect a corresponding decrease 
in C (number of cubic feet used per niinute), the aim of the practical engineer 




FIG. 128. — SERGEANT AIR REHEATER. 

should be directed towards reheating and expansive working. The cost of re- 
heating is about one-eighth of a pound of coal per horse power per hour. 

AIR MOTOR. 

Most air motors in use at the present time have been designed after the 
steam engine ; in fact, the steam engine is often converted into an air engine with 
very good results. Considering, however, the difference in the properties of 
both fluids, there is no doubt that higher efficiencies can be attained when the 
motor is especially designed for the use of air. 

Fig. 122 represents also a theoretical card taken from an air engine, and 
shows the volume of air taken in at the compressor to be contracted from C to 
D, due to falling temperature, and when it reaches the motor it is about 60° F. 
If it is used expansively, then the expansion line will be (D R) ; great cold will 



USE. 



369 



result, and the theoretical temperature at R will be about -155" F., and if moisture 
is contained in the air it will cause freezing of the exhaust ports unless provision 
is made for abstracting it. 

If heat could be supplied during expansion, we would be able to trace the 
isothermal D B, and there would be no loss at all. This is impossible, of course, 
and the efficiency is, as here shown, about 50 per cent. Now, if the air is heated 
before it is admitted to the motor, the volum.e would increase from D to C, and 
if expansion took place along C B (adiabatic), we would get back all the work 
that was put into the air in the compressor, taking out, of course, valve resistance 
and other losses incident to transmission. Continuing this argument, if it were 
possible to use the air in the motor-cylinder at temperature above 350° to 400° F., 







FIG. 129. 



we would be able to obtain more work from the air than was originally expended 
upon it, at a very small additional cost for reheating. 

We have just seen that by reheating the air we increase its energy in pro- 
portion to the heat applied, or — 

W=Cp (Ti — ^Tg) foot pounds of energy supplied to every pound (at constant 
pressure. ) 

Aside from this thcrmo-dynamic gain, we also overcome the danger of 
freezing at the exhaust port in the motor, for the temperature of exhaust is raised 
above that of the freezing point. 

REHEATERS. 

There are various practical methods of reheating. The most prominent arc: 
I) Applying heat through metal surfaces. 
II) Internal reheating. 



370 



USE. 



SERGEANT REHEATER. 

One of the jfirst class is shown in Fig. 128, and is knoAvn as the Sergeant 
Reheater. This reheater consists of two cast iron shells, which are bolted to- 
gether. Air enters the annular space at the top and passes in thin layers over the 
walls of the heater into the annular space at the bottom, which forms the outlet. 
In appearance it resembles a truncated cone. The advantage of this form is to 
keep the velocity of the air constant. The air being hot, it has greater volume, 






.v^^^^^^A^W■^^'■^^^^'.^.s'.^W■^^;^y^^T:<? 



^^^^^^^^^^^^^^^■■^^^■^^w,^w,'\^^■^^l■s^^^^^^^'.'.^^-.^^^^^vv.<k^^^^^^^^^^^^ < ?OT^ ; 



FIG. 130. — PARKE REHEATER. 



and would consequently increase the friction if there was no room for expansion.! 
The fuel may be either gas, oil or coal, or coke; when made for coal or coke, it[ 
will be supplied at the top, and the ash will be drawn from the bottom. 

Tests have been made with this heater, and the results show that 340 cubic 
feet of free air per minute, at 40 pounds pressure, can be reheated to 360° F. This 
is equivalent to a gain of 35 per cent, imparted to the energy of a pound of air| 
The capacity of this reheater is given as 400 cubic ft. of free air per minute. 



USE. 



371 



SAUNDERS' INTERNAL REHEATING. 

Fig. 129 represents a reheater of the second class, known as an internal re- 
heater — i. €., where the air comes in direct contact with the fire. This illustration 
represents the reheater actually applied to a rock drill. It is placed between the 
throttle valve and steam chest, and represents an enlarged pipe fitting, with a wire 
gauze to keep the coal or coke, which is in an incandescent state, from blowing 
into the steam-chest. Coke or charcoal is supplied through an opening at the 
top, which is then securely fastened. This method of reheating ought to be very 
economical and effective. The air supplies the oxygen which promotes combus- 
tion, and the resulting heat is transmitted direct into the motor cylinder. 

PARKE REHEATER. 

In the Parke Reheater, shown in Fig. 130, fuel is admitted at 9; 8 is a hop- 
per, and 5 the grate ; 2 the ash pit, and 10 an opening to blow out ashes. The air 
is supplied through the pipe 3, and it passes over hot coals and out through pipe 
4, then into a thermostat; 15 is a bar made of metal, with a high coefficient of 
expansion; 13 is a double valve, and 14 is the outlet; 16 is a regulating screw. 
When the temperature is too high, the bar 15 expands, and, working through 




FIG. 131. — HARDIE REHEATER. 



levers, 17 and 18 helps to shut off the supply of hot air and at the same time ad- 
mits cold air through 12, thus reducing the temperature and keeping it uniform. 
The adjustment can be made so that the temperature will not vary 5 degrees. 
There is necessarily a limit to the temperature of the air at wlwch it may be ad- 
mitted to the motor, and this is about 300° to 350** F. The pipe for transmitting 
the air will have to be well covered to keep the air heated at this high temperature, 
as air parts with its heat as easily as it takes it up. 

Another method of reheating, and one which has met with a very high de- 
gree of success, both in this country and abroad, is a system of passing the air 
through hot water under pressure on its way into the motor cylinder (Fig. 131). 
This system is in vogue in the Hardie motor, and has given good results, some of 
which are given in the table (Table 40). 

The water in this tank is heated by blowing a jet of live steam into it, and 
the air passes through fine openings into the water at the bottom of the tank. In 
passing through the water the air takes with it some of this water in the form of 
vapor, passing through the perforations in the pipe in the top of the tank and then 
out into the cylinder. 'J'he advantage of this steam in the cylinder is twofold — 
(a) lubrication of cylinder and preventing leakage past piston; (b) the air in ex- 



372 



USE, 



panding draws upon the latent heat of the steam, and therefore brings the ex- 
pansion nearer to the isothermal. 



TABLE FOR REHEATING. 

Table 40 shows the comparative values of different methods of reheating, 
as determined by experiment at Frabrick Street, Fargeau. The hot air and water 
injection method seems to have given by far the best results, the efficiency of the 
fluid being almost double that of the cold air. 

SEPARATOR. 

Sometimes it is not practical to reheat the air, especially when the motor is 
being moved from place to place; and then if the motor works air expansively, 
the danger due to freezing can be successfully overcome by means of a separator 
placed in the pipe near the motor. 

An experiment was made at Cornell University, with which I am familiar, 
to operate a small slide valve engine with air at an initial temperature of 40° F. 
A separator was made out of a 6-Inch pipe, with caps on both ends. The air was 
drawn from this separator at right angles to the supply; the moisture In the air 
was thrown against the sides of the separator and ran to the bottom, where it was 
drawn off from time to time by a small drip-cock. This experiment was suc- 
cessful, and the engine did not stall when we reached as low a temperature as 3" 
F. (A lower temperature might have been reached but for the fact that the en- 
gine was cutting off at % stroke.) 



TABLE 40 — COMPARATIVE TESTS OF COMPRESSED AIR MOTORS AT FABRIK ST., FARGEAU, 
USING COLD AIR, HOT AIR, AND HOT AIR WITH WATER INJECTION. 



Description. 


Cold Air. 


Hot Air. 


Hot Ait 
and Water 
Injection. 


Weight of air used per 1 H. P. per hour in cylinder . . 

Volume " " " " 


63.65 lbs. 

822.7 cu. ft. 
13.7 " 

62° F. 
—67° F. 
46.2 p. c. 


45.526 lbs. 

586.14 cu. ft. 

9.76 " 

392" F. 

32° F. 

64 8 p. c. 


33.59 lbs. 
432.55 cu. ft. 


Volume of air used per 1 H P per minute 


7.2 " 




392° F. 


" (exhaust) 

Total efficiency of fluid 


122° F, 
86.9 p. c. 





(Abstract from paper of Jos. Francais in " Seraing Belgien," 1888.) 

The consumption of free air per minute, when reheated, has been stated for 
the Paris air motors, by a writer of authority, to be from 11 to 15 cubic feet per i 
H. P. per minute, and when using air cold, 15 to 25 cubic feet per i h. p. per 
minute. 

HARDIE MOTOR. 

In the Hardie Motor tested by W. K. Lanman and myself in May, 1895, 
we found the consumption of free air per minute to be from 6 to 6.7 cubic feet 
per I H. p. 

In this test our object was to determine the most economical working pres- 
sure, and also to determine the efficiency of the reheater. We made 7 runs with 



USE. 



373 



initial pressures ranging from 55 pounds to 140 pounds per square inch. Every 
other condition was kept as nearly constant as possible. The air was passed 
through the hot water in the reheater, but as the heat stored in the water was 
gradually becoming less, the efficiency diminished from beginning to end of run. 
This can be shown by a set of curves if desired. 

Table 41 shows some results of tests of the Hardie Motor. 

TABLE 41. — ABSTRACT FROM TEST Of HARDIE MOTOR, AT ROME, N. Y., MAY, 1895. 



Number or Run. 



Average working pressure lbs., sq. in 

Distance run in miles 

—Reheater— 

Temp, of air entering heater 

Terap. of air leaving heater 

Temp, of air at exhaust 

Degrees taken up by air in passing through 

heater 

Difference in temp, in heater, begin, and 

end run 

Indicated horse power 

Pounds of water used during run 

Air used per 1 H. P. per minute, cu. ft 

Per cent, of power obtained from heater. . . 



I. 


II. 


III. 


IV. 


V. 


VI. 


54.6 
1.14 


69.6 
2.49 


91.9 
2.96 


100.2 
3.27 


116.8 
3.25 


141. 
3.58 


780 F. 
210« 
127° 


70.8« 

248 

148.6 


67.6 
197.5 
108. 


615 
247.5 
146.7 


63. 
197. 
104.4 


65.2 
240.3 
130.7 


132° 


177. 


129.9 


186. 


134 


175.1 


18° 


21 


30 


47 


28 


49 


3 

15 08 

7.7 

41.4 


7.1 
25.7 

6.4 
46.5 


9.79 
30.35 

6.1 
32.5 


11.9 

27.6 

6.1 

47. 


10.86 
12.1 
6.6 
36. 


12.45 
29.37 

6 
43.2 




I. 


II. 


I. 


li. 


I. 



VII. 



133. 
1..57 



19C.7 
99. 

125.7 

16 

11.19 

10.05 

6.7 

34.6 

II. 



There were two runs made with one charge of hot water, and the second 
run in each case necessarily shows a lower efficiency, due principally to loss of 
heat from the reheater. If the reheater could be supplied with heat during the 
entire run, there is no doubt that the above figure of 6 cubic feet per minute can 
be still further reduced. The power obtained from the reheater was about 45 
per cent, of the total power developed. We made one run without hot water in 
the reheater, but as the temperature of the tank was still above 100° F. when we 
started our run, the consumption of free air per minute was 8.8 cubic feet. Other 
experiments made since, show that when the tank is at atmospheric temperature 
the consumption is about 12 cubic feet, so that when this motor is working with 
cold air it is as economical as the foreign motors, of which we have given figures 
above, working hot air. 

In the Hardie Motor the air is compressed to a pressure of 2,000 pounds 
per square inch. It is stored in Mannesmann seamless tubes, which are shaped 
like a bottle with a round bottom. At the neck copper tubes are screwed in se- 
curely, and there are 16 tubes, and each 7J/2 inches diameter, but of different 
length, so as to utilize all dead spaces under the car body. These tubes are tested 
to 4,000 pounds pressure, and are all connected so as to form one receiver. The 
capacity in cubic feet is about 45, which means that the free air capacity is about 
6,000 cubic feet. The car will be able to travel about 15 miles on one charge. 

The power to compress 6,000 cubic feet per minute in a four stage com- 



374 USE. 

pressor will be about 3,000 h. p., if done in one minute, and in 5 minutes it will 
take a 600 H. p. compressor. 

Since it is not practical to use air at such high pressures in the cylinder, on 
acctnuit of losses due to clearance, this pressure is reduced by means of a reducing 
valve, and air is admitted to the reheater and then to the cylinder at about 140 
pounds per square inch. This great loss, due to wire drawing, is compensated for 
in the storage, for with such a supply (6,000 cubic feet) there need be no delay 
and inconvenience due to recharging until the power house is reached. 

If it could be arranged to keep the water heated throughout the run, there 
is no doubt that the efficiency of this motor would be very much increased. 

Chairman — If any of the members desire to ask Mr. Weber any questions, 
I think he will take pleasure in answering. 

Student — 1 should like to ask Mr. Weber how these air motors compare 
in efficiency with other forms of motors? 

Mr. ]\\'bcr — The efficiency is high. The compressed air motor is usually 
as high as that of the steam engine; and, as I said, if special designs were made 
for air, they would be still higher. There is a report published of tests made in 
Paris by Prof. Unwin, on small rotating air motors, and I think it showed from 
80 to 85 per cent. I don't know the exact figures. 

Student — In that reheater you spoke of, invented by \Mr. Saunders, where 
the air comes in direct contact with the heated coals, I should think there would 
be trouble from ashes being carried into the cylinder. 

Mr. Weber — Mr. Parke overcomes all that. I think his reheater is an 
improvement over Mr. Saunders' reheater, for he furnishes a constant supply at 
constant temperature, which is very important at times ; but Mr. Saunders' idea 
is a g\x>d one for such rough work as with drills. 

Student — I should think some sort of electrical reheater could be used. 

Mr. Weber — I can refer you to an article by Mr. Wm. L. Saunders in 
"Cassier's Magazine," 1892, a reprint of his lecture on compressed air before the 
Franklin Institute of Philadelphia he speaks of some electrical devices. 



ECONOMIES IN THE USE OF COMPRESSED AIR. 



An Inlet Cooler which Saved Five Per Cent. — Suggestions Regarding the 

Suction Valve Chamber — Staging and Intercooling, and How 

THE Latter Might Be Improved. 



Advantages of Compressed Air Over Other Sources of Power in Deep Mining- 
Great Developments Predicted. 



BY r. r. whitelaw.* 

It seems strange that although compressed air has been used chiefly in 
mines for hoisting, pumping, coal cutting and various devices for the last 50 
years, little or nothing has been done towards making it an economical method — 
•Paper read before the Mechanical Engineer's Association of South Africa. 



USE. 375 

whether on account of the difficulties which have presented themselves in the 
form of heat or cold, or a general indifference to its use, I am not in a position 
to say — but I am inclined to think it is the latter, as our greatest engineers and 
experimenters have lived during that period; and had they devoted the same 
attention to this subject as they have given to steam and electricity, compressed 
air would stand on a much higher level than it does to-day, and there would be 
but little use for electricity. 

In about the year 1849 an air compressor plant was installed in Glasgow 
for driving an underground air hoist; the compressor, I might say, was a fast 
running one, and but little attention was giving to cooling devices, and the result 
was that it had not run many hours before the cylinders and pipes close to the 
compressor were red hot; in fact, the engineer thought they would melt, and 
then the report came up from below that the engine had frozen up; this was 
thought to be a great phenpmenon, and was talked about all over the country. 
The freezing was caused by over-expansion, and yet the difficulty was got over 
without changing the ratio — by injecting a spray of water into the compressor 
cylinder the temperature was reduced to such an extent that there was no diffi- 
culty in running the compressor. The moisture thus injected was then carried 
over to the hoist and. prevented the freezing up of the exhaust ports. Had the 
air been dry in the first instance (I might say there is no such thing as dry air) 
freezing up could not have taken place, and yet it was prevented by still adding 
more water to it. This may seem strange, yet it was so ; for air with a high 
percentage of water has a much higher specific heat value than dry air, so that in 
the first place it is more difficult to heat, and in the second it is more difficult to 
cool. In round numbers, dry air at 140 deg. F. initial temperature, with a ratio 
expansion of 2, is reduced to 32 deg. F., whilst moist air with the same initial 
temperature is only reduced to 2^ deg. F. after four expansions. The same ap- 
plies to the compression of air. Atmospheric air at 68 deg. F. initial tempera- 
ture, when compressed to 100 lbs. pressure, rises, if dry, without cooling to 490 
deg. p., and if sufficiently moist to 194 deg. F. only. 

The practice of injecting water into the compressor cylinder is being car- 
ried out to the present day in some of the Scotch collieries, and so long as it will 
run their engines they are satisfied, and the difficulty for them is ended ; 
a few tons of coal per week is of no importance in their calculations ; thus com- 
pressed air is, by Scotch coal owners and by many other users, left to work out 
its own salvation. It is wasteful even to the extent of 50 to 60 per cent., and we 
only use it where we cannot use steam ; that is how compressed air is abused, and 
I really think there are more abusers than users of it. 

When the air is compressed all the work which is done in the compression 
is converted into heat, and from this it would seem that as soon as all the heat 
has been got rid of the work done on the air is virtually thrown away, and the 
air will have not more energy than it had before compression if the temperature 
is not increased. It is quite true that it has no more energy than it had before 
compression, but the advantage lies in bringing it into a more available form. 
The heat of compression increases the volume, and it is, therefore, necessary to 
have a much larger compressor than if no heat was generated. The first cause of 
loss of work then is theoretically unavoidable, but then theory and practice are 



376 USE. 

very different things, more especially in air compression — for instance, theory 
says that time plays no part in the heating of air during compression, whilst 
practice says the faster you run your compressor the higher the temperature will 
rise. That is quite true, but in the first instance the heat is lost by radiation, 
whilst in the second case, we cannot lose it as it has not time to get away, and this 
is the task we have to set ourselves to — viz., to get rid of the heat during the 
compression, or, if possible, before compression. 

All makers of compressors in giving instructions how to use these ma- 
chines advise taking the air from the cool or shaded side of the engine-room, 
so that the air will enter the compressor as cool as possible, and, therefore, it will 
occupy a smaller space and be so much cooler when compressed. You must bear 
in mind that every 5 deg. F. you reduce it in this way means i per cent, saving. 
Now the question arises, can this cooling before entering the compressor be ex- 
tended beyond taking the air from the cool side of the house? It can, and the 
following method I tried at the Pearl Central with a new Riedler air compressor 
that had the advantage of two inlets to the suction valve chambers, one opening 
to the engine-room and the other could be led under the floor. The latter was 
carried down about 10 ft., and then a drive was cut from there to a distance of 
about 40 ft., then a shaft was driven down to meet this. An old chimney was 
put down the shaft and on top of the chimney there was fixed a large spray about 
3 ft. in diameter — very little water was used to keep a decent shower going all 
the time, and the water not only cooled the air, but washed away all the dust. 
The results got from this were more than I expected, as the air was cooled 15 
deg. F., showing a saving of about 3 per cent., and the engine-room temperature 
was 10 deg. F. higher than the outside air, so that I have a right to claim 25 deg. 
F. of cooling, or effecting a saving of 5 per cent, over taking the air from the 
warm room. The result was excellent, as the cost of installing the cooler was 
very small. The inlet cooler could be still further improved upon by having a 
fan blast to blow along the tunnel, and if compressed air was used anywhere 
close by for driving a pump or a hammer it could also be exhausted into the 
tunnel; so you will see that it is possible to effect a further cooling of about 10 
deg. F. to 12 deg. F. 

Another point that ought to be attended to is the suction valve chamber. 
With some compressors nothing can be done, but in the present Reidler the 
arrangement is simply splendid for having a trickling cooler keeping the cham- 
ber cool, as working at present the suction- chamber is nearly as hot as any part 
of the machine, and the result is that the air in passing takes up a considerable 
amount of the heat from the walls, and is expanded just on the point of entering 
the cylinder. The degree the air is heated at this point cannot be arrived at, but 
it is just possible that it is something like 20 deg. F. If it were only possible to 
prevent 10 deg. F. of this amount it would mean that another 2 per cent, added to 
the 5 per cent, we arrived at previously would make in all a saving of 7 per cent., 
which is a large item where 500 or 600 horse-power is being developed for making 
compressed air on a plant such as I have made mention of, or, in other words, on 
a 45-drill plant it would mean a saving in round numbers of £46 per month. 

Having done all we can for a single stage compressor, little else can be 
accomplished unless by injecting a spray of water into the air while it is being 
compressed. To do this properly it would require an arrangement of tappet 



USE. 377 

valves so as to give it the spray at the right moment. If this arrangement was 
well carried out, I believe most excellent results would be obtained. The en- 
trained water would be liberated as soon as the temperature dropped sufficiently 
and could be then trapped with an ordinary steam trap. 

Jacket-cooling is practically of no service except in assisting lubrication of 
the cylinder, so that little can be gained by jacketing the cylinder and heads and 
piston, as only a thin layer of the air that comes in contact with the metal sur- 
faces is cooled. 

We now come to the staging of the air. This has been the means of al- 
ready reducing the cost of compressed air by about 20 per cent. Now, what does 
staging do after all? Well, it simply draws away the heat from the air whilst it 
is being compressed, and this we have already decided is the great difficulty we 
have to overcome. Suppose', for instance, air is compressed by an indefinite 
number of stages, and that each time the air is cooled to free air temperature, 
what do we attain? Very nearly isothermal compression, and this is what we 
want to attain so that no loss will take place after the air has left the com- 
pressor. The gain is two-fold: first, less power is developed; and, secondly, the 
air is delivered cold, and will, therefore, have no loss due to reduction in volume, 
which is the bugbear of compressed air as used at present. 

Air expands and contracts as its absolute temperature. For instance, we 
have, two compressors, one a single stage and the other a double stage. The 
other is delivering air at 500 deg. F., and the latter 200 deg. F., or say 961 deg. 
and 661 deg. F. absolute. The relative efficiencies are as 961 deg. is to 661 deg., 
or the latter has an advantage over the former of 24 per cent. So that I hope 
you will agree with me that staging and efficient intercooling are what is re- 
quired to elevate compressed air to a first place for the transmission of power. 

Inter-cooling between stages, as carried out at present in many cases, is 
far from perfect. Inter-coolers are made after the same form as feedwater 
heaters or condensers with a great number of tubes which are very liable to 
leakage. The tubes get coated with lime and other matters, which considerably 
reduce their efficiency. The best result that I know of is a reduction of tem- 
perature of from 200 deg. F. to 140 deg. F., while the air, to give full value, should 
be reduced to at least 72 deg. F., or free air temperature. 1 think a method could 
be adopted whereby the air could be reduced to free air temperature, and a really 
simple method, too. I find that air delivered from a single stage air compressor 
at a temperature of 470 deg. F. has been reduced to free air temperature before 
it has traveled 250 feet through the delivery pipe. This is one of the great draw- 
backs to the use of compressed air ; it is a decided disadvantage, but it might be 
taken advantage of for inter-cooling. What could be more simple for an inter- 
cooler than 200 ft. of pipes, even if it were 20 or 30 per cent, larger than is 
actually required? It would be much cheaper in the first place than the ordinary 
inter-cooler, if it was well laid down in the first instance — there is no reason why 
it should be looked at again, it would require no circulating water, if it was made 
large enough there would be no loss due to friction — it is a natural process, whilst 
the other is artificial. Any one of you can have a practical demonstration of it 
by fixing a thermometer to the air main. The pipe should not be buried into the 
ground, as earth is a good non-conductor of heat, and would give back heat to the 
air. It should be exposed to the atmosphere, and placed where it would get a free 



378 USE. 

current of air, and should not be exposed to the sun. The present inter-cooler, as 
I have already mentioned, reduces the temperature to 140 deg. F., which I think 
is one of the best results that can be obtained, whilst the inter-cooler, already- 
suggested, would reduce the temperature to say, at the very least, 70 deg. F., or a 
saving of 14 per cent, over the present system of inter-cooling. . The figures I 
have just given refer to second stage compression, where the air is first com- 
pressed to 25 lbs. pressure and from 25 lbs. direct to 80 lbs. with a temperature 
of about 280 deg. F., from which temperature it is generally reduced to 70 deg. 
F., a drop of 210, showing a loss of exactly 28 per cent, from the time it leaves 
the compressor till the time it reaches the drills. The above figures work out as 
follows: — 280 gives 741 absolute, 70 gives 531, and 741 : 531 : : 100 : 71.6, show- 
ing a difference on the wrong side of 28.6 per cent. — which is the actual per- 
centage of loss. This is where better inter-cooling would give the advantage if 
the air was delivered at 70 deg. F. less, or 210 deg. F., the actual loss would only 
be 20 per cent. The remedies for this are three stage compression and reheating. 

First, let us take three stages, and say the second stage raises the pressure 
from 25 lbs. to 60 lbs., and the temperature to 120 deg. F., and is again cooled 
down to free air temperattire. It is well known that the temperature rises more 
rapidly in the early stages of compression than it does in the latter stages. For 
instance, from atmospheric temperature to 25 lbs. gauge it is raised from 80 to 290 
deg., or an increase of 212 deg. F., whilst from 25 to 80 lbs. it is raised from 135 
to 276 deg., an increase of 141 deg. In the first case, the pressure is only in- 
creased 25 lbs., and in the second case, the pressure is increased 55 lbs. This, I 
should say, speaks well for three stage air compression. The initial cost of such 
a compressor would certainly be much greater, but that would soon be made up 
in the increased economy. The temperature, as I have already pointed out, by 
compressing from 25 to 60 deg. would be 120 deg. F. The air is then cooled to 
free air temperature and is sent on its last journey to 80 lbs.; the temperature 
would then be increased to about no deg. F., and this would be its final tem- 
perature. It has then only a drop of 40 deg. F. until it reaches free air tempera- 
ture. The loss sustained by this fall in the temperature would then only repre- 
sent 7 per cent, with a two stage air compressor, showing a gain of 21 per cent, 
in favor of three stage air compression over two stages. 

The cost of such a machine would be much greater than a two stage com- 
pressor; so is a triple expansion engine a great deal more expensive than a com- 
pound, but still they are being extensively used, and why? " Because the economy 
in running soon makes up for any extra initial cost. The same argument applies 
to three stage air compression. 

I think it would be unfair of me to conclude my paper without touching on 
reheating, which is a very important factor in the use of compressed air. It is 
argued by many prominent engineers that the reheating of air for use in rock 
drills is a very difficult matter. More difficult problems than this have presented 
themselves to the engineering world and have been mastered, so also will the 
reheating of air for use in rock drills. Air at a low temperature has very little 
cooling effect upon water or other bodies it comes in contact with. The appli- 
cation of this, inversely applied, is of great advantage in the use of compressed 
air for the transmission of power, or, in other words, it requires but very little 



USE. 379 

heat to raise the temperature rapidly; in fact, there is no other source of energy 
to which heat can be applied with the same economical results. 

It is well known that after the transmission of compressed air to the point 
where it is to be employed a considerable saving of cost can be effected by re- 
heating immediately before using. It can be easily shown that where air has 
been compressed to a certain pressure, and has by transmission to any reasonable 
distance been reduced to its normal temperature, if the air is reheated and ex- 
panded, the extra volume resulting from the expansion is produced by an ex- 
penditure of heat much less than the original volume was produced for. Let us 
assume, then, for the sake of easy computation, that air is being compressed to 75 
lbs. by steam at the same pressure, and that 2 cubic feet of steam are required for 
the production of i cubic foot of air, the weight of i cubic foot of steam at 75 
lbs. is .208 lbs., and the total units of heat in i lb. of steam at 75 lbs. are 1151, 
therefore, the total units of heat in i cubic foot of steam are, in round numbers, 
239. To produce i cubic foot of air at 75 lbs., will be required 239x2 B. T. U., or 
478 B. T. U. As air at constant pressure expands or contracts at its absolute 
temperature, it is easy to show the quantity of heat required to double the volume 
of air at any temperature. We will again assume that we have got i cubic foot 
of air at 75 lbs, pressure and at 60 deg. F., or an absolute temperature of 521 deg. 
To double the volume we require to double the absolute temperature or, 521X 
21042, deducting from this 461, would leave the temperature by thermometric 
measurement to be 581, showing an increase of temperature of 581 — 60, or 521 
deg. F. The specific heat of air at a constant pressure is .237, or nearly a quarter 
of the specific heat of water. The Aveight of i cubic foot of air at 75 lbs. pres- 
sure is .456 lbs., the actual heat expended, then, in doubling the original cubic 
foot of air at 60 deg. F., is 521, the temperature x.237, the specific heat x.457, the 
weight in lbs. — or 56.3 B. T. U., or as nearly as possible, 12 per cent, of what it 
took in heat units to produce it in the first instance. Of course, we cannot ex- 
pect to get a reheater that will give the full heat value of the coal, but it is quite 
reasonable to expect at least 70 per cent, efficiency from the coal, which can be 
easily got from a good steam boiler with suitable coal. This would work out at 
20 per cent, of the original cost of the air to exactly double the volume — such a 
result as this could not be got at in actual practice. The temperature — viz., 581 
deg. F., is too high, and, again, it is not possible to produce air at 600 deg. F. 
without such a series of staging and inter-cooling that it would make the process 
of air compression too difficult. Anyhow, with two stage air compression air 
can be produced at 280 deg. F. Suppose it is then reduced to 60 deg. F. by 
transmission and storage, the loss incurred is 30 per cent., due to contraction in 
volume. We would, therefore, require 50 per cent, of the original heat units to 
double the volume of the air. I do not mean to say that even such a good result 
as that could be obtained, but I do say this, that it is the duty of all engineers to 
do their utmost to endeavor to get as near to it as possible and raise to its proper 
level the most natural source of energy that exists in nature. 

The reheating of air also makes it possible to use it expansively without 
fear of freezing up the exhaust ports; in fact, the temperature could be regu- 
lated to suit any reasonable cut-off, so that the temperature would not fall below 
32 deg. F. without reheating. With dry air two expansions are all that can be 
got, whilst with reheated air it is possible to get five and six expansions, more so 



38o USE. 

if the air is well saturated. Reheating with steam has been used with very good 
results, and, where found convenient, steam should be always used with air. 
Suppose a steam reheater was used for a pump within a reasonable distance from 
where a rock drill was being used, and the condensed steam was' trapped, the 
trapped water would be led into a launder lying nearly level, so that the water 
would fill the launder. The air pipe leading to the drills is then immersed in the 
water, which would have a temperature of probably 140 deg. F. The air would 
have the same temperature as the water. Suppose it was only 100 deg. F. when 
delivered at the drills, it would always give a little help towards economy. 

In the matter of economy, in generating and in distributing compressed 
air, if proper care is exercised so that the machine is as nearly perfect as can be, 
the receivers and the pipe main perfectly free from leakage, with only one safety 
valve, no matter how many receivers there are on the distributing main, and that 
one safety valve fitted with a good strong siren that will make the attendant wish 
he had been more careful every time it blows off, the transmission of power by 
compressed air should be at the very least equal to any other method. Whilst 
compressed air has many disadvantages, it has also many advantages that other 
sources of energy have not got. For instance, in deep mining such as we will 
have in the Rand presently, when depths of 2,000 and 3,000 ft. will be quite com- 
mon, and temperature of between 90 deg. and 100 deg. F. compressed air will 
gain where electricity would lose. First, the weight of air in the column will 
add to the pressure, not to a great extent, but probably quite enough to make up 
for what has been lost in friction; at a depth of 2,000 ft. with air at 80 lbs. 
pressure on the surface, there would be a pressure of something like 87}^ lbs. 
in the mine. Then, again, supposing the temperature of the atmosphere was 
60 deg.,and the temperature of the mine was 96 deg., at 3,000 ft. the air would 
be reheated 36 deg. F., showing a gain of about 4 per cent., the mine itself acting 
as a reheater. Thus, it will be seen that for deep mining, where high tempera- 
ture may be expected, compressed air will increase in economy, whilst, as I have 
already endeavored to point out, other sources of energy would keep on losing 
and regain nothing. Although not yet in economy, yet in many other ways does 
compressed air appeal to the mechanical engineer; it is perfectly safe, accidents 
caused by compressed air are so very rare that they are practically unknown. 
Should an air pipe burst, no harm is done except the loss that is caused by leak- 
age. As a proof of its growing popularity, we have only to take up the adver- 
tisement columns of an engineering paper, and we find that the different ap- 
pliances that are operated by compressed air are simply innumerable. We read 
about pneumatic painters, pneumatic cranes, and pneumatic so many different 
things, that I could stand here for another hour doing nothing else but reading 
over a list of the different appliances that are operated by compressed air. In 
fact, it would seem that it is just beginning to dawn upon the engineering world 
that the greatest force in nature is the air we breathe when put into the proper 
form. And now that the first blush of electricity has worn off, and scientific 
men are looking for new fields of thought, I think I am safe in predicting that 
compressed air will come in for a considerable amount of attention, and great 
developments may be looked for during the next few years. 



USE. 381 

THE EFFICIENCY OF COMPRESSED AIR ENGINES. 

The increasing- use which is being made of compressed air engines for 
mine and underground work stimulates the inquiry regarding their efficiency. By 
this is meant the percentage of power given out by the air engine bears to the 
power required to compress it. 

The situation is apparently very simple. An engine drives an air com- 
pressor or compressing cylinder which forces air into a reservoir. The air under 
pressure is let through pipes to the various air engines, and is there used in the 
same manner as steam. 

The resulting power is frequently a small portion of the power expended. In 
a large number of cases the fault is due to poor designing, and is not due to the 
fault of the system. 

The losses are chargeable in a great many cases to fault of the com- 
pressor. This ordinarily Js 15 per cent, but has been as low as 6 per cent., the 
average being about 12 per cent, in the common type of compressors; some of 
the high grade Corliss ehgiliea running air compressor will work on an average 
of less than 10 per cent. After the compressor we have the loss occasioned by 
pumping the air from the engine room, which would naturally be warm; there- 
fore being lighter and less dense, this loss varies from 3 to 10 per cent. 

Next the losses arising in the air cylinders. In sufficient supply, difficult 
discharge, defective cooling and a host of other things which perplex the de- 
signer and robs the owner of power. Next comes the loss in the pipes. This 
has, therefore, received by no means the consideration it should. The loss 
varies with every condition, and is somewhat perplexing. The next loss is due 
to fall of temperature in the cylinders of an engine, and often gives serious 
trouble. Losses often arise from leakage in pipes, and are too evident to call 
for much debate. No leak can be too small not to require prompt attention. The 
parties who are entrusted with the use of compressed air often permit loss which 
no engineering skill can prevent. We can only realize 100 per cent, efficiency in 
an air engine, leaving friction out of the question, when the changes of tem- 
perature are exactly the reverse in the air engine to those in air cylinder of the 
compressor, but these conditions can hardly be realized. 

The air during compression becomes heated, and during expansion be- 
comes cold. If the air immediately after compression and before losing any 
heat, could be expanded back to atmospheric pressure, it would on being ex- 
hausted have the same temperature as before, and consequently would exert as 
much power as it took to compress it (less friction). 

But the loss of heat after compression and before being used again cannot 
be prevented. 

We can by reheating with a very small amount of fuel expand the air and 
bring it up to nearly 100 per cent, efficiency. Consideration must be had for the 
friction of compressor and air engine. 

We find for ordinary pressures, say 60 lbs., that the decrease in resistance 
to compression which is secured by the cooling attachment or improved circulating 
device, is equal to the friction of the compressor. Hence, it is safe in calculating 
the efficiency of the air engine, to consider the compressor as working without 
rooling attachment and working without friction. 



382 USE. 

The result of such calculation would be too high for low pressures, and 
too low for high pressures. This, of course, is due to the fact that air at low 
pressure contains less heat than at high pressures. 

Following is a table which gives nearly the correct efficiency of air under 
various pressures: 

Gauge pressure — 2.9 lbs. 94.85 per cent, efficiency. 



14.7 " 


81.5 


29.4 " 


72.75 


44.1 " 


67.00 


58.8 " 


63.00 


73-5 " 


56.7s " 


88.2 " 


56.75 " 



We observe the efficiencies of the lower pressure are much higher than that 
of the high pressure, and would be supposed to be most economical, but such is 
not the case, as air under a low pressure requires a much larger engine to do the 
work, and will therefore consume more air per h. p. than a smaller engine with 
higher pressure. 

The matter of determining the efficiency of an air compressor varies so 
widely that it is impossible to lay down a rule to meet all conditions; hence, we 
have to test every case separately, but ordinarily the efficiency of an air com- 
pressor can be taken at about 50 per cent. ; under certain conditions it might be 
taken at 60 per cent. a. w. tubes. 



METERING COMPRESSED AIR. 

As the installation of compressed air Central Plants for distributing power 
is gaining daily in importance, the problem of measuring the amount of com- 
pressed air at certain pressures used by any consumer confronts not only the 
Central Plant owners but also the consumer. The consumer should know how 
much air he uses in order to know that he is charged reasonably for it, and the 
Central Plant owners must also know how much every consumer uses in order 
to avoid abuse and to ascertain whether the plant is operated on a paying basis. 

Thus the Central Plant owners having a main supply pipe which may be 
branched off for distributing to mines or manufacturing establishments will find 
the necessity of installing meters and other apparatus which cannot be tampered 
with, and which at the end of each month will be able to give, not only themselves, 
but also the consumer proper data, from which the bills for the month can be 
figured. 

The only way to properly determine the amount of compressed air used 
by any single consumer is to determine the amount of free air, which, if multi- 
plied by the mean average pressure, will give the total amount of energy fur- 
nished. 

The Equitable Meter Co. of Pittsburg has studied the problem of metering 
compressed air for a number of years and are now manufacturing meters which 
we understand are giving very good satisfaction ; as tests which have been made 



USE. 



383 



show that the readings vary but a very small percentage from the actual. Their 
standard size meters for compressed air, which we illustrate herewith, will carry 
a working pressure of 100 lbs. They have, however, made some high pressure 
meters for measuring compressed natural gas up to 500 lbs. pressure. The meters 
are made in five sizes, as follows : 10,000, 20,000, 30,000, 40,000 and 50,000 cubic 
ft. maximum capacity per hour. The reader will, of course, understand that the 
amount of an- passing through a meter duri'ng a certain time means the amount of 
air in cubic feet at the pressure at which it passes through the meter, no matter 
if the air pressure is i lb. or 100 lbs. to the square inch, and then to find the total 




FIG. 132. — COMi'RESSED AIK METER. 



volume of free air passed, the volume of compres.sed air will have to be reduced 
into a volume of free air. 

We are also informed that there is very little pressure absorbed by the 
meter while the air passes through it, the pressure absorption being only about 
I o^., no matter what the air pressure is. These air meters are provided with a 
special back pressure relief valve, preventing the wrecking of the meter in case 
high pressure air would be let into the meter or taken out of it too suddenly. 

The next question of importance to be considered is for both producer and 
ronsumer to know that the air pressure is as steady as possible, and sufficient 
to run the apparatus to be operated by compressed air, as there would be no use 
for a consumer to pay for a larger volume of compressed air at 50 lbs. pressure 



384 USE. 

should he require 80 lbs. pressure, as a large quantity of air at a low pressure 
would not do his work; thus it would be necessary to install a compressed air 
Pressure Recording Gauge in connection with each meter, and at the end of the 
month the mean average pressure could be figured and this multiplied by the 
number of cubic feet of free air, the product representing the energy furnished, 
would enable both producer and consumer to settle upon the amount to be paid. 

The problem has been explained clearly enough, but it may be added, how- 
ever, that it would always be advisable to install a small receiver next to the 
meter and that the pressure recording gauge should be connected with this 
receiver; this, not only to avoid the vibration of recording finger, but also to 
prevent any shock to the meter. 

It should be noted also that a consumer situated far away from the Central 
Power Plant should pay more per unit of energy than one near by, for the reason 
that the friction in long pipes amounts to a certain percentage of power, and 
that a long pipe line is more subject to leaks and requires more attention than a 
short one. 

The reader will, of course, also understand that it is impossible to give 
an idea of the charge which should be made per unit of power, as the cost of 
producing compressed air varies considerably, according to localities, size of 
plant, whether plant is operated by steam or water power, whether, if operated 
by steam the engines are economical or not; but there is one thing certain, which 
is that if a Central Power Plant even be operated by steam and this plant would 
be of 1,000 horse power, equipped with compound Corliss Engines, and would 
supply compressed air to, say five consumers, it should prove a great financial 
success, as it would save each consumer the installation of a small 200 horse 
power plant. These five 200-horse power plants costing much more by at least 
30 per cent, and not being as economical by at least 60 per cent, as a first-class 
1,000-horse power plant. 

In addition each consumer would require a fireman and engineer, while the 
Central Plant could be operated practically at the same expense for labor as a 
single 200-horse power plant. 



VOLUMES OF AIR USED IN ENGINES. 

The present increasing demand for the use of compressed air as a motive 
power necessarily involves the use of intricate mathematical formulae for estimat- 
ing relative sizes of Compressors and Air Engines, etc. 

Quite a number of these formulae have been worked out to cover average 
practical conditions and are daily serving a very useful purpose in the form of 
tables. 

A very intricate formula is the one based upon the use of free air per min- 
ute per Indicated Horse Power in an Air Engine, and as a problem is often stated 
in terms of the I. H. P. of the motor — to find the quantity of free air per minute 
required; — the following table which has not been published up to the present 
time, will facilitate computations of this kind and is in such shape that it will not 
require any extended knowledge of mathematics. 



USE. 



385 



As will be seen from the table, the only data required is the guage pressure 
and point of cut-off; having those two items given, we find from the table the 
free air required per I. H. P., and it will only be necessary to multiply this amount 
by the total I. H. P. of the motor to determine the total quantity of free air re- 
quired and consequently the size of an Air Compressor to furnish the air. 

These figures do not take account of clearance, but it will be an easy mat- 
ter to add the per cent, of clearance after having determined the total amount of 
free air required. 

It will also be noticed that the free air consumption is based upon the use 
of cold air, i. e., Initial temperature of air at 60" F. In case reheating is resorted 
to there will be a corresponding decrease in the amount used depending upon the 
temperature of air at admission to motor, and will be proportional to the ratio of 
T. 

— where T2 4604-60=520° F. absolute temperature and T3=46o + temperature 
T3 
of air at admission to motor. 

Thus if the air is reheated to 300° F., the quantity in the table will have to 
4(30+60 520. .684 

be multiplied by .:=« = 

460+300 760. 

TABLE 42. — AIR USED [CU. FT, FREE AIR PER MIN.] PER I. H. P. IN MOTOR [WITHOUT 

RE-HEATING.] 

GAUGE PRESSURBS. 



POINT OF 
CUT orF 


15 


80 


40 


50 


60 


70 


80 


90 


100 


110 


125 


150 


1 


31.2 


23.3 


21.3 


20.2 


19.4 


18.8 


18.42 


18.10 


17.8 


17.62 


17.40 


17.05 


Yx 


25.6 


18.7 


17.1 


16.1 


15.47 


15.0 


14.6 


14.35 


14.15 


13.98 


13.78 


13.50 


% 


21.8 


17.85 


162 


15.2 


14.50 


14.2 


13.75 


13.47 


13.28 


13.08 


12.90 


12.60 


\i 


25.8 


16.4 


14.5 


13.5 


12.8 


12.3 


11.93 


11.7 


11.48 


11.30 


11.10 


10.85 


Vs 


37.0 


17.5 


15.2 


12.9 


11.85 


11.26 


10.8 


10.5 


10.21 


10.02 


9.78 


9.50 


H 


167. 


20.6 


15.6 


13.4 


13.3 


11.40 


10.72 


10 31 


10.0 


9.75 


9.42 


9.10 



A further use of this table is to find the most economical point of cut-off 
for gauge pressures from 15 lbs. to 150 lbs. per square inch. This fact is apparent 
from a study of each vertical column; thus at 60 lbs. pressure, the lowest con- 
sumption of free air per I. H. P., is at 1-3 cut-off, while a 40 lbs. pressure will 
work most economically at 1/2 cut-off. f. c. weber. 

Copyright, 1896. 



THE AIR MOTOR. 



A TRIAL TRIP ON THE ELEVATED RAILROAD, NEW YORK. 

The Hardie Air Motor, which was built by the American Air Power Co., 
to demonstrate the possibility of using it to draw trains on the Manhattan Ele- 



386 USE. 

vated Railroad, New York City, was put into service on Thursday evening, Aug. 
19, and a public test of it was made by taking a train loaded with 192 persons 
over the Sixth Avenue road from Rector street to Fifty-eighth street and back j 
to Cortlandt street. 

The motor, with five cars attached, started a little after nine o'clock. 
Robert Hardie, the inventor, was in charge of the engine, having a regular engi- 
neer as pilot. 

The train followed -a regular train and made the run in 19 minutes, this 
being 3 minutes faster than the scheduled time. The time on the return trip, 
making all stops, was 2^ minutes. 

Among the passengers were a large number of representative railroad men 
and men interested in compressed air matters. Every one admitted that the trial 
was most successful and all that could be desired. 

The Hardie Compressed Air Locomotive in its main features of construe- ' 
tion is substantially identical with that of the steam locomotives in use by the. 
Manhattan Railway. Its length is the same, its driving wheels the same, but its 
maximum weight when manned and ready for service is less than that of the 
steam locomotive. The wheel base of the driving wheels being six feet instead 
of five feet, as on the steam locomotive, makes it permissable to place a greater 
weight on the drivers than is allowable on the steam locomotives, without in- 
creasing the strain on the structure, thus giving it increased tractive power and 
enabling it to take the sharp curves on the line easier. The cylinders are 13 
inches in diameter by 20 inches stroke, and the valves are specially designed. The 
variable cut-off is controlled by a hand wheel in place of the notched quadrant 
used on the steam locomotives. Two independent ways are provided for applying 
the air brakes, and in addition the locomotive has a compressed air-driving wheel- 
brake of novel design, thus affording additional security against accident. In 
place of the boiler and firebox of the steam locomotive, there is a bundle or nest 
of seamless steel flasks, 9 inches in diameter and about 15 feet long, having a 
total capacity of about 150 cu. ft,, in which the air compressed to 2,400 lbs. pres- 
sure per sq. inch, is stored. In operation, the compressed air passes from these 
flasks through a regulating valve and is delivered at a uniform pressure into a 
low pressure receiver, where the air is re-heated by passing through hot water 
and is then applied to the cylinders at a uniform working pressure of 150 lbs. 
per square inch. The method of storing the air reducing the pressure, re-heating 
and controlling, as well -as the application to the cylinder, is the result of many 
years of study and experimental work by Mr. Hardie, whose efforts have been 
unequalled. 

The air to charge this locomotive is compressed at 100 Greenwich street 
by an Ingersoll-Sergeant four-stage compressor, and conveyed by pipe line 
through Greenwich street to Rector street, and thence up Rector street to the 
Sixth Avenue Elevated structure, to the point where the steam locomotives take 
their water. It does not take any more time to charge this locomotive with air 
suflficietit for a run to Fifty-eighth street and back, than it does to take water on 
an ordinary steam locomotive. The Mannesmann tubes furnished by Chas. G. 
Eckstein & Co., 45 Vesey street. New York, are in use both on the motor and in 
the power house. 



USE. 3«7 

THE USEFULNESS OF COMPRESSED AIR UNDER DIFFICULTIES. 

Another example of the usefulness of compressed air as a means of 
solving difficult engineering problems is afforded by the sinking of a caisson 
for the purpose of building a lighthouse at the mouth of the Potomac River, 
Chesapeake Bay. 

A few years ago this lighthouse was built at what was known as Smith 
Point, a dangerous location where opposing tides and currents have built up 
shoals of sand which extend eight or ten miles out into the Bay. Severe wrecks 
had occurred on this shoal until it was determined to put a light just at the 
edge of the channel about eight miles from the shore and about one hundred and 
twenty miles south of Baltimore. The work was begun in 1896 and completed 
in about one year. The sinking of the caisson was the most difficult part of it 
and this was almost impossible except through that valuable auxiliary — com- 
pressed air. The caisson was such as is usally employed and an air compressor, 
boiler and other appurtenances were placed on the top and somewhat exposed 
to the waves during the storms. This work was successfully accomplished, the 
air being used to give life to the men beneath the surface who dug within the 
great iron cylinder until it rested upon a secure foundation. So long as the 
air compressor was kept working on the surface all was peace below, where the 
storms were not felt. 

This is only a type which emphasizes the importance of compressed air in 
this valuable field of foundation building. Foundations for bridges are built in 
the same way and it would be difficult to find a means by which the huge dif- 
ficulties encountered in this kind of work would be overcome without the aid of 
compressed air. 



SAFETY IN AIR. 



Compressed air is the safest of all powers. No other power or means of 
transmitting power compares with it in safety. This quality is one of great im- 
portance and is, we think, underestimated by those who advocate the use of com- 
pressed air. We have been carrying on for some months a series of editorials in 
this paper reciting cases where explosions have occurred in compressed air pas- 
sages, and have been in a general way discussing the subject. It may have sur- 
prised some of our readers to hear so much about explosions in compressed air, 
and in fact we have been asked the question why we dwell so much upon a sub- 
ject which only furnishes ammunition to electrical engineers. Our only answer 
is that compressed air can stand this sort of thing. Its freedom from explosions 
and its extreme safety in use, are so well known and so far beyond dispute when 
comparing air with electric or any other power, that we are encouraged at all 
times to search out cases where air has been shown to be unsafe, running them 
down by getting at all the facts, and pointing out where the fault lies so that 
such things may be stopped. Nothing of any great importance in industrial use 
is absolutely safe: Railway trains meet with accidents, bridges sometimes fall, 
buildings collapse, boilers explode, and yet no one thinks of abandoning the use 
of these things because they are unsafe. Compared with the number of build- 



388 USE. 

ings that fall, accidents of this kind are rare, and taking into consideration the 
number of boilers which are in use explosions are not serious, and when we 
consider the large number of compressed air installations using air, varying in 
pressure from i lb. to 3,000 lbs. to the square inch, an explosion is a rare 
occurrence. Every passenger train and a good many freight trains on every rail- 
road of magnitude in the world is equipped with air compressors and storage 
tanks containing compressed air at considerable pressures, yet who ever heard 
of an air explosion on a railroad train? Most of the railroad shops and most 
of the machine shops in America have air plants. Nearly every mine of mag- 
nitude, where the ore is hard and where mining operations are carried on on a 
large scale, is equipped with a compressed air plant, and yet how many of us 
have heard of explosions there? A large number of compressed air installations 
are in use as permanent plants lifting water from driven wells : Caissons are 
commonly used for excavations under water: Tunnels through hard and soft 
ground invariably use compressed air: Street cars have been in use more than 
ten years in France, and during recent years in New York, with air as a motive 
power : Foundries are now equipped with air compressing plants, which are con- 
sidered just as essential to their existence as the foundry crane: Coal mining 
machines, though in some cases propelled by electricity, chiefly use air; Quarries 
are equipped with air plants : Ships are provided with air compressors for refrig- 
erating purpeses: Air is used to some extent for lifting sewage, and yet how 
seldom do we hear of explosions or accidents due to the use of compressed air. 
The reason for this is very plain. Air is a harmless elastic fluid, non-com- 
bustible, healthy, and it is the most widely distributed of all substances. We 
simply compress it and hold it in a condition of confinement, and must provide 
a vessel strong enough to overcome its elasticity. Unlike steam, air has no 
reserved force when in confinement. The destructive effect of a boiler explosion 
is mainly due to the sudden conversion into steam of large volumes of super- 
heated water, held in a condition of water by the pressure of steam on top of it. 
Here we have a reserve force. With air when once a vent occurs the pressure 
falls very rapidly and the strain is soon relieved. This rapid fall of pressure is 
due to two things, expansion of the air from a smaller space into a larger one, 
and a rapid reduction in the volume of this air, due to shrinkage in expansion 
by cooling. Liquid air is produced by expanding compressed air down to atmos- 
pheric pressure, the intense cold being utilized to liquefy volumes of compressed 
air. This cooling effect takes place when air is expanded, and the rapid shrink- 
age of volume follows. 

Now, as a matter of fact, no accidents occur in the use of compressed air 
that may not be traced to explosions through the ignition of oil or inflammable 
substances which are used with the air. If we throw kerosene oil into the inlet 
valve of a compressor," we are likely to have an explosion because this oil may 
meet with a temperature which is higher than its flashing point, and so with cer- 
tain low grades of lubricating oils; but the air itself is perfectly safe, it being 
merely necessary to -confine it in a receiver or pipe which is strong enough to 
hold it. This is not a serious problem, and in the case of air the factor of safety 
is not nearly so great as where steam, water, gas or other substances are 
similarly confined, because air does not corrode the vessel, its temperature is not 



USE. 389 

changed, nor is there any liability of internal destructive action taking place, 
hence, it will be generally admitted that air, except through the course of com- 
pression, is as near the point of absolute safety as anything of this class can be. 
The elements of danger are therefore confined to the compressor, or, more 
properly speaking, to the compressing plant, and it is to this subject that we have 
been devoting our attention. Should some one discover a lubricant for air com- 
pressor cylinders which is not composed of a carbon, there would be no further 
occasion for discussion on this subject. It is simply because of the elements of 
uncertainty attending the use of oil that explosions in compressed air are made 
possible, and it is also because of ignorance as to the causes of these explosions 
and the carelessness on the part of the engineers that we hear anything about 
the subject. 

Engineers get in the habit of feeding oil to the air cylinders as they would 
to steam cylinders, and compressed air generating plants are sometimes run so 
carelessly that proper attention to the causes producing explosions is not given. 
As the use' of compressed air grows it becomes better understood, and the more 
we understand it the more we are convinced of its great safety and cleanness. 
Men are not afraid of a machine run by compressed air. There is no dread in 
their mind to upset their nerves. We are told that this feeling of dread exists 
among men handling electric machines, especially in mines. The electric current 
is a mysterious thing. It gives a shock, and it is not an uncommon thing for 
persons to read that electric shocks have produced death. It is known that in two 
States in America electric execution has replaced hanging, and all these things 
combine to add to the terrors of this great and mysterious form of nature's 
energy. Fires are becoming more frequent in large cities. Insurance statistics 
point to the serious effect which electricity has had in producing fires. Elec- 
trolysis is a destructive agent, directly traceable to the large use of electric 
power in cities, and all these things combine to make more plain the absolute 
simplicity and safety of pneumatic power. 



A WAR-SHIP RUN BY AIR. 



Machinery which May Revolutionize Naval Methods. 

Of all the vessels of the new United States Navy, the monitor Ter- 
ror is perhaps the most interesting. She is not by any means, the original 
"cheese-box on a raft," for her two turrets, smokestack, armored ventila- 
tor, etc., form a varied superstructure, very different from the single, low, round 
turret of Ericsson's Monitor. Quite a number of years back Congress appro- 
priated money to build five of these vessels— the Puritan, Amphitrite, Miantono- 
mah, Monadnock and Terror — but the appropriation was only sufficient to com- 
plete the hulls, and they lay unfinished until about six years ago. Then further 
appropriations were secured, and the vessels have been gradually completed. The 
Puritan is not yet entirely fitted up, and the Terror has but lately gone into com- 
mission, having recently been on a trial cruise of two weeks. 



390 USE. 

The Terror differs from her sisters in that the Navy Department contracted 
with the Pneumatic Gun and Power Company to install pneumatic machinery 
upon the Terror only, for turning the turrets, working the guns, steering the ship, 
etc. The other monitors have hydraulic machinery for their turrets and guns, 
and are steered by steam. The Terror, indeed, is the only vessel, in all the navies 
of the world, in which pneumatic power is thus applied, and is therefore a prac- 
tical experiment whose success may lead to far wider use of the pneumatic prin- 
ciple. 

The use of compressed air has several advantages over steam or hydraulic 
power. All pipes are liable to leak ; and a leak in a steam or water pipe, in a tur- 
ret crowded with guns and machinery in action, is inconvenient, if not dangerous, 
and requires both time and patience to repair it, when neither is likely to be avail- 
able. In an air tube, on the contrary, a leak causes no inconvenience — since the 
waft of air from it would be rather agreeable to the men at the guns than other- 
wise — ^and, with a surplus of supply air, requires no immediate repair. Again, 
steam and water systems require exhaust pipes, whereas in the pneumatic system 
the exhaust is turned either into the turret or the open air, as desired. 

The Terror has two engines for compressing the air, one situated in the 
hold near the forward turret, and the other on the berth deck near the after turret. 
Either of these, singly, can supply sufficient air, at a pressure of 125 feet per 
square inch to operate both turrets, including the guns — a total weight of nearly 
500 tons. The compressor takes its supply of air from the chamber in which the 
engine stands, and compresses it in two cylinders, sending it also through two con- 
densing cylinders, where it is cooled by circulating seawater. It is then carried 
by pipes and two engines, of two cylinders each, situated on each turret floor, pre- 
cisely like steam-engines, about fourteen-inch stroke and eight inches diameter 
of cylinder. These develop about forty horse-power each, and are controlled by a 
lever in the sighting hood of the turret, over and between the guns, where are 
also situated the elevating levers. The movement of both turret and guns is thus 
controlled by the officer who sights and fires the latter. 

Beneath the turret-chamber proper, where the guns are mounted, is the 
loading-chamber, with the magazine on its starboard, and the shell-room on its 
port side. The shell, which weighs 500 pounds, and a cartridge, in two parts, 
containing 240 pounds of powder, are run out into the loading room by a single 
overhead trolley, and dropped into a lift, which is swung around until the shell is 
opposite a loading car, into the lower compartment of which it is slid, partly by its 
own weight, while the cartridge is placed in the upper division. The car is then 
hoisted to the breech of the gun, by means of another pneumatic cylinder, placed 
upright between the guns. The car stops, automatically, when the shell is oppo- 
site the breech-chamber, and the rammer (telescopic in form, and also operated by 
compressed air) pushes the shell to its seat, and the cartridges follow. Usually, 
m these heavy guns, a loading-tray is placed in the breech to facilitate the entrance 
of shell and cartridges ; but in the Terror the loading-car, as it ascends, throws the 
tray automatically into position, and when the loading is finished the tray is 
thrown out again, and the breech-block thrust into place by the pneumatic ram- 
mer, thus leaving the gun in complete readiness to be fired. So thorough and per- 
fect are all these automatic adjustments, that the guns in either turret can be 
loaded independently, and in any position of train or elevation. All parts of the 



USE. 391 

gun-carriage and turret move together, except one^-that being the fixed central 
column through which the air pipes and communication pipes pass into the turret 
and up to the sighting-hood. 

To elevate and depress the guns, there is on either side the turret a cylinder, 
containing glycerine and water, which is forced by compressed air into the elevat- 
ing ram under the breech of the gun. This is regulated by double valves, and is 
controlled, also, by the officer who sights the guns. The guns are fired, either 
independently or together, by means of an electric push-button. The crew for the 
two guns of a turret comprises ten men.' This is somewhat of a change from the 
time of the civil war, when twenty-five men were required to work a single heavy 
gun. 

The recoil of the guns is controlled by two pneumatic cylinders, forty inches 
in length and fourteen in diameter. Before firing, these cylinders have a pressure, 
on the recoil side of the piston, of about 500 pounds per square inch, which is 
drawn from a special plunger attached to the compressing engine. The recoil 
cylinders are secured to the gun carriage, and the pistons to the gun. When the 
gun is fired, the pressure upon the recoil side of the piston is rapidly increased by 
compression. A tapered rod, passing through the centre of the piston, permits 
the air to pass more and more freely to the counter side, thus equalizing the pres- 
sure at the end of the recoil. By this simple arrangement, the recoil of the guns 
is limited to about thirty-four inches. At the end of the recoil, the pressure upon 
the recoil side of the piston operates upon a greater area, and immediately returns 
the gun to its place. The recoil and counter-recoil are both without shock, the 
air cushion preventing' any sudden stopping of either. 

The ship is also steered by compressed air, the steering-room being abaft 
the cabin. The shaft which operates the pneumatic valve has three clutches upon 
it besides the steering-wheel, by means of which the control of the rudder may be 
transferred to either turret, or to the pilot-house. The Terror is also fitted with 
an electric motor of five horse-power, and with hand-wheels, so that she can be 
steered either by electricity or by hand, if necessary. In actual size, she is about 
one-half as large as the Indiana class of battleships, but in proportion is far more 
powerful. She has a displacement of 4,000 tons, and is 260 feet long and 56 feet 
beam. She draws is feet of water, and with 250 tons of ammunition on board 
and her bunkers full of coal, her freeboard is only 27 inches or so. In an 
ordinary sea, therefore, her deck is more or less awash, and this renders her a 
peculiarly elusive target to the enemy. Her speed is about 10 knots, which is 
ample for the purposes for which she is intended. 

With the new smokeless powder, her four ten-inch guns will give each of 
their 500 pound projectiles an initial velocity of about 2,400 feet per second which 
gives an energy of about 20,000 foot-tons — a force which, applied properly, would 
be sufficient to lift the Terror herself bodily five feet at each shot; and as these 
guns can be fired at the rate one gun every thirty seconds (the turret revolving 
once a minute), some idea of her power may thus be gained. The guns carry 
seven or eight miles, and a fair shot can be made two miles away. — Evening Post. 



392 USE. 

PROPOSED EXTENSION' OF THE USE OF COMPRESSED AIR ON 

MEN-OF-WAR. 



BY F. w. bartlett; p. a. engr., u. s. n. 

Compressed air is now used for certain purposes on men-of-war, as, for 
charging torpedoes ; in combination with water for elevating guns and ! unning 
them out ; for turning turrets ; for steering engines, and for ash hoists. 

It seems possible and feasible to extend this use, and the object of this 
article is to suggest some other ways of using air and to state why air is better 
for many purposes than either steam or electricity. 

Air of various degrees of compression may be used for nearly all pur- 
poses on board ship, except for the main engines and possibly the dynamos. It 
could be used for running the dynamos as well, and it is only a question with 
these whether the economic loss would be balanced by the gains in efficiency, 
comfort, etc. 

It is to be borne well in mind that one of the most serious troubles to be 
contended with on board men-of-war of modern types is the suffering due to heat 
and lack of proper ventilation, the debilitation and discomforts in summer, being 
excessive in cool latitudes and over-powering in hot ones. 

An attempt will be made to describe a theoretical arrangement showing the 
proposed changes, using air in place of steam where possible, economy being per- 
haps sacrificed for the sake of making life bearable in hot weather on men-of- 
war, and in order to have the officers and crew in condition to put forth their 
best efforts when called upon in emergencies. 

THEORETICAL ARRANGEMENT FOR THE USE OF AIR MORE EXTENSIVELY. 

As near the middle of the length of the ship as possible, preferably be- 
tween sets of boilers, so that the most direct and shortest steam pipe may lead 
to the plant, no matter which boiler may be in use, there is an auxiliary plant 
room, where is located every auxiliary machine in the ship that can be placed 
there, so that a machinist and oiler on watch may be able to take care of them 
all, and not have six or eight men on watch in detached parts of the ship. Here 
are placed the two auxiliary condensers, three evaporators and distillers, heating 
and ventilating machine, fire-room blowers, ice machine, dynamos, duplicate air 
compressors and reservoirs for the pressures required, as described later. These 
are all operated by steam for the sake of economy, as they all run with constancy 
when once started. 

Besides the steam pipes for the main engines and this short auxiliary pipe 
for the central plant, the only steam pipes in the ship are those very small ones 
leading to the galley and pantries. This lessens materially the trouble due to 
heat, it being confined to a small portion of the length of the ship in port, 
and to only about a third at sea. The exhaust pipes are all in the central plant 
room and are short, the auxiliary condensers being close at hand. Thus the heat 
from this pipe is also in one compartment only. Another important gain here 
is in the fact that there is at all times a high vacuum in the condensers, all the 
leakages being in this one room and easily cared for, instead of there being many 
detached steam-using machines all over the ship, run by all sorts of persons, 



USE. 393 

many of them not knowing enough to close exhaust valves and drains when 
through running a machine, and others not caring to take the trouble even if 
they know enough. 

Aside from the traps for the main engines, there are only six traps in the 
ship — one from each evaporator, one for the auxiliary steam pipe, one from the 
galley pipe and one from the pantry pipe. All of these six traps are in the cen- 
tral plant room, and are accessible and readily kept in good order. The dis- 
charges from these traps all go into the auxiliary exhaust pipe, as the loss of 
heat is small, and not important, compared with keeping the ship bearable in hot 
weather. This prevents also the constant discharge of vapor from the escape 
pipe. The discharge pipes from the traps for the main engines are led into the 
main feed tanks in the engine rooms, and all the pipes lead to near the bottom 
of the tanks, so that as much of the vapor as possible may be condensed. It 
was not considered advisable to lead the drains from the main engine traps to 
the auxiliary exhaUst pipe in the distant central plant room, as too much heat 
would be disseminated on the way. 

The discharges from the auxiliary condensers lead to a tank in the same 
room, this tank being connected with the main feed tanks by a pipe, the water 
flowing by gravity, from the higher tank in the central plant room, a non-return 
valve preventing vapor from returning from the main tanks. 

Thus the steam used in the ship, and the consequent heating, is only for 
the main engines and the central plant room, and the functions of the steam are 
reduced to a minimum, as far as the number of machines operated is concerned. 
Of course the air compressors are of considerable power and the pressure 
accumulators large, to allow for emergencies. These latter, however, occupy the 
upper part of the room, and are as concentrated as possible. The room is kept 
cool by its special ventilation, so that the temperature of the air in the accumu- 
lators is never much over that of the water outside of the ship, which is used 
in cooling the air. The specially designed pressure regulators for the accumula- 
tors allow of a large surplus of air ready for any sudden call, so that the air 
compressors may fill all the chambers full when little air is being used. 

Besides the special compressors for the high pressure needed for the tor- 
pedoes, of which there are two, as now provided on our large ships, there are 
duplicate compressors and reservoirs, or accumulators, that keep up a constant 
pressure of 60 pounds per square inch. 

This pressure is kept constant by the action of the pressure regulators of 
the reservoirs acting on the throttle of the compressor, and the mechanism is 
found efficient for all emergencies, the pressure never dropping over 5 pounds 
at any time, and that only when a crane and anchor engine happen to be sud- 
denly put in use at the same instant. At such times, however, warning is given, 
so that the steam stop valve outside the throttle of the air compressor engine 
may be opened wider, to allow for the sudden addition of such great quantities 
of work. Signals have previously been sent to the central plant room, to open 
air to the pipes for these machines, as explained below. In getting under way, 
and at drills when the turrets are likely to be used suddenly, both of the com- 
pressors are in operation to insure greater steadiness of pressure, but ordinarily 
one is amply sufficient for all needs. 



394 USE. 

In easy reach of tbe two attendants are valves plainly marked on the air 
pipes leading to each machine outside of the central plant room. Each of these 
machines has its own pipe, so that a large machine opening from a pipe may not 
throw out a smaller one, as happens with the steam pipes ordinarily in use. By 
this means absolute uniformity of air pressure is secured for each machine, the 
sizes of pipes to each being calculated for the work to be done. At a signal 
from any part of the ship, the air is turned on and the machine is ready for 
use at once. The throttle valve at the machine is the only valve that the at- 
tendant in the distant part of the ship needs to touch. Having no exhaust 
valve and no drains to attend to, the operator has a simple operation to perform, 
only oiling the machine. After use, closing the throttle valve secures the ma- 
chine. No harm is done if a signal be not sent to the central plant room 
when finished with the machine, so that the valve may be closed there 
as a possible slight leak of air is the only trouble that can ensue. 
The pipe is left filled with air at the full pressure, and this air is 
always ready to do its work. No vacuum is destroyed by ignorance or careless- 
ness. No return exhaust pipe is required, one small pipe carrying the power, 
the exhaust being into the atmosphere. The air to be used is drawn down from 
the ventilators, and passes around and among pipes filled with running water, 
so that a portion of the moisture in the air is condensed and tapped off. There 
are also separators where needed for removing the moisture from the air after it 
is compressed. The temperature of the air may be readily varied to any degree 
not below that of the sea water, by reducing or increasing the quantity of the 
circulating water, regulating the temperature of the discharge water and of the 
air compressed. By opening and closing the large exhaust ventilating doors at 
the top of the central plant room, the air in the accumulators may be kept at the 
temperature of the atmosphere, or as much higher as desired. 

The engines in the different parts of the ship are all of the same type, but 
of three different sizes, thus making parts interchangeable and doing away with 
the carrying of many spare parts. The pipes to these machines are also of three 
sizes. Where a great power is required, as for turrets or anchor engine, two 
of the largest sizes of machines are attached to one shaft. The machines are 
small, three-cylinder, simple, long stroke, light and fast running, the air expand- 
ing just enough to prevent the formation of ice at the exhaust nozzles, the pres- 
sure at discharge being slightly above the atmospheric pressure. At the ex- 
haust openings there are mufflers constructed of a non-resonant substance, thus 
preventing much noise. These engines are geared down for the work they have 
to do, thus enabling the three sizes of machines to handle all the various kinds 
and quantities of work to be done in the ship. 

This system does away with the enormous prices paid for special ma- 
chines all over the ship. 

The following list shows the uses to which air is put on board: 

To operate— Main engine auxiliaries; auxiliary, fire, bilge and water ser- 
vice dumps; steering engine; anchor engine; boat cranes; winches; turret-turn- 
ing engines; hydraulic cylinders for working guns; ammunition hoists; ash hy- 
dro-pneumatic hoists ; feed pumps ; smoke hose for guns ; whistle and siren. 

Other uses: To send messages to clear a compartment of water when 
flooded; to ventilate; to heat and cool the ship. 



USE. 395 

Air is better than steam for auxiliary use on board ship, for the following 
reasons : 

The ship is cooler in summer, and men are not debilitated by the heat; 
there are no hot bulkheads all over the ship; the auxiliary machinery and pipes 
last much longer; half the number of valves, pipes, etc., are needed; there are no 
ventilating blowers, the heater lines doing the work; there is great saving in 
cost of plants and in the cost of oil ; no pipe coverings are needed ; the machines 
are ready for use at once; there are fewer men on watch in port, and more for 
general work; the launch is ready at any moment, at sea or in port; there is no 
smoke, heat, etc., and only one man is required. 

It is needless to say that all the machinery is in charge of the chief engi- 
neer of the ship. 

It is certain that something must be done to relieve the officers and crew 
of our men-of-war of the suffering from the terrible heat on these ships in sum- 
mer. — American Machinist. 



COMPRESSED AIR IN EUROPE. 

The delivery wagon shown in Fig. 133, constructed by Messrs. Molas, 
Lamielle and Tessier, was exhibited at the second Exposition des Tuile'ries, 
where it attracted considerable attention by reason of the relative simplicity of 
arrangement of its maneuvering devices and the limited amount of space occi;pied 
by the motive apparatus. 

In this vehicle, the air-storage reservoirs employed consist of hammered steel 
tubes of 8-inch external diameter, the ratio of the weight of which to that of the 
air stored up isHf^^is. The heating is done directly by gasoline, instead of by 
steam from a boiler, as in the Mekarski system; the manufacturers being of the 
opinion that, since a direct heating of the air permits it to be raised to a tempera- 
ture much higher than that which would be obtained by means of heating by 
steam, they obtain also a greater increase of volume and, consequently, of work 
that compensates for the heating during expansion obtained with the above-named 
system. 

The stove, burners, and gasoline reservoir used for heating have here a 
feeble weight as compared with the arrangement in which a boiler is employed. 
The ratio of the weight of air stored up to that of the reservoirs and heating ap- 
paratus does not descend below ji-. 

The air reservoirs are eleven in number and are distributed in two groups, 
one of six forming the "battery," and the other of five constituting the "reserve." 
The capacity of these groups is respectively, 11 and 7.5 cubic feet, or, altogether, 
18.5 cubic feet. 

With a charging pressure of 4,290 pounds to the square inch, the weight of 
air stored up, at a temperature of 13*' C, is 1,100 X 2.7 X638 = 392,370 pounds. 

Before its admission to the cylinders of the motor, the air passes into a steel 
worm of .28-inch internal diameter, of .14-inch thickness, and of a length of 19.7 
teet. which raises its temperature to a figure that varies with the discharge of air 
and the intensity of the burners that heat the worm. The temperature may thus 
reach 150 C. The air afterward passes into an expander (maneuvered by the 



396 



USE. 



driver), which lowers its pressure by about from ii to 44 pounds, according to the 
difficulties of the road, the load and the speed. This expansion of the air gives 
rise to a lowering of the temperature, in order to raise which, the air thus 
expanded is made to pass into a second worm concentric with the first and heated 
by the same burners. When the air makes its exit from this second worm, its 
temperature may be as high as 250°. It is claimed that this double heating is 
capable of more than doubling the volume, and, consequently, the work of the 
air stored up. This air is then admitted to the cylinders through an expansion 
distribution with a special change of speed. The admission takes place upon 
only one of the faces of each piston, and the motor is thus a single acting one. 
But the cylinders are four in number, and cast in pairs, and the connecting rods 





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FIG. 133. — COMl'RESSEU AIR DELIVERY WAGON USED IN PARIS. 



(jointed directly to the pistons) actuate the same shaft, the cranks of which are 
set at an angle of 180° per group, and at 90° from one group to the other. The 
motor thus has the same power as a two-cylinder double-acting engine. The 
arrangement adopted offers numerous advantages, and permits especially of sup- 
pressing the shocks at the joints of the connecting rods that occur in double- 
acting engines at the time of the change of direction of the piston ; of doing away 
with piston-rod stuffing-boxes, which it is often difficult to keep tight, and which 
absorb a certain amount of work in friction ; of removing and putting in place a 
connecting rod and its piston without having to dismount a cylinder bottom. 

The space available for a motor under the seat of a carriage is sufficient 
widthwise, but not lengthwise ; and so the motor must occupy more space in the 
former than in the latter direction. Now, two double-acting cylinders of the same 



USE. 397 

bore, placed either longitudinally or vertically, always take up more space than 
the single-acting four-cylinder arrangement adopted; and from this fact, it has 
been possible to have a greater available space for occupancy by the reservoirs of 
compressed air. 

The distribution is affected by means of cams and valves. The opening of 
the latter takes place very rapidly. Their closing, on the contrary, occurs gradu- 
ally, and is hastened or retarded through the shifting of the reversing lever, 
according to the admission that is desired. The minimum admission employed is 
10 per cent., but this may be increased to 60 per cent, for starting. The exhaust 
and the compression are fixed, and have a duration of 20 per cent, of the stroke of 
the pistons. 

There is no special cut-off of fluid between the expander and the cylinder 
admission valves. These latter open wide for all admissions between 10 and 60 
per cent, of the forward and backward running of the engine. 

The burners, which are three in number, are arranged beneath the worms 
in an iron plate-jacket 10.75 inches in diameter and 12 inches in height, surmounted 
by a chimney which leads the gases of combustion to the top of the roof of the 
vehicle. The burners are supplied by a gasoline reservoir of a capacity of about 
ten quarts in which an air pressure of from 45 to 70 pounds to the square inch 
is created. The pipe that leads the gasoline to the burners may be partially closed 
by a screw plug. Through such arrangements, it is possible for the driver of the 
wagon to proportion the intensity of the heating to the output of air, so as to 
obtain a temperature that is always sensibly the same. 

The quantity of gasoline consumed by the burners is about 15 ounces per 
hour of running; but this might easily be increased if it were found that the 
operation of the motor became thereby more economical. 

The motor rests upon the floor of the carriage, beneath the seat occupied 
by the driver, who can thus examine it while it is running. Its rotary velocity 
for a speed of five miles an hour made by the vehicle is 200 revolutions per 
minute. The transmission is effected by means of chains of the "Varietur" sys- 
tem, which connects two sprockets, keyed at the extremities of the driving-shaft, 
with two toothed wheels of six times larger diameter fixed through bolts to the 
spokes of the hind wheels. The power of the motor, upon the crank-shaft, is 20 
horse at a velocity of 300 revolutions, and at a pressure of 285 pounds. 

The differential consists of two friction-cones fixed near the extremities of 
the driving-shaft and actuated by the steering apparatus. The control of these 
cones is such that, in a turning about, the adhesion of the one that is situated at 
the side of the internal wheel diminishes in such a way as to permit of a certain 
amount of sliding of the cone in its socket, and, consequently, of a retardation in 
the revolution of the corresponding wheel ; while the adhesion of the cone sit- 
uated at the side of the wheel that is to traverse the wide radius increases, so that 
no sliding in its socket can occur, despite the greater resistance of the wheel that 
is moving ahead. 

The pivoting can thus be effected upon a driving wheel that is rendered 
absolutely immovable, from the view-point of revolution, and, consequently, in a 
circle having as a radius the distance of such wheel from the opposite wheel of the 
front axle, and that, too, in running forward as well as backward. 



398 USE. 

The steering is done by means of a hand wheel keyed upon the axis of an 
endless screw, which gears from a toothed wheel keyed upon the shaft of the 
reversing gearing situated beneath the vehicle. An indicator placed before the 
eyes of the driver exactly reproduces the changes in direction of the axis of the 
vehicle's path, and thus permits him to keep in a straight line. 

The intermediate screw lengthens the maneuvering, but renders it sure, 
stable and gentle. Such an arrangement, however, offers advantages only for 
heavy vehicles designed for running always at a low speed. 

Finally, let us say that the accumulators are placed longitudinally under 
the floor of the vehicle in two superposed rows, and are connected by easily acces- 
sible couplings placed in the rear. Movable panels permit of an inspection and 
of a tightening of the joints and couplings. 

The motor and vehicle as a whole are well elaborated and denote upon the 
part of the manufacturers the possession of real ingenuity and a complete knowl- 
edge of the question with which they had to deal.— TA^ Automobile Magazine. 



REHEATING COMPRESSED AIR. 

The importance of reheating compressed air is as yet but little understood. 
Theoretically, reheating offers great economical advantages; practically, these 
advantages have not been attained, largely, we think, because of the lack of expe- 
rience. There are, of course, limitations to reheating; it is not practical, for in- 
stance, to use dry, hot air in the cylinder of an engine at temperatures much 
above 350°, but even if the air is heated to 300** and used at that temperature the 
increase in volume which this effects under constant pressure is large and im- 
portant. Under normal conditions, say at 60° temperature, air reheated to about 
300** will be increased in volume nearly 50 per cent. It has been claimed by en- 
gineers who have tested reheaters applied to pneumatic motors, that a storage 
tank of given volume and pressure has been used to propel a car 3% miles with 
cold air, and at the same volume and pressure when used with heated air, the car 
was propelled 6^4 miles. 

We recall a personal experience last year during the tests of the Hardie 
motor on 125th street. New York: a car which had been making three trips with 
a single storage of air was unable to make but two trips, when it was discovered 
that the steam which was used at the terminal station to reheat the storage water 
on the car had so far run down in pressure that, notwithstanding the fact that 
the hose had been coupled to the tank as usual, yet the water received only a 
part of the accustomed temperature. This was not discovered because the motor- 
man omitted to keep a record of the initial temperature at the charging station. 

It has been shown by figures and is claimed by those of experience, that 
the cost in heat units of the increased volume of air produced by reheating is 
from one-sixth to one-eighth of the cost of an equal volume when produced by 
the process of compression. 

In connection with this subject the following letters are interesting as 
pointing to a practical system of reheating first used, we think, by Mr. Rix on the 
Pacific Coast. The availability and simplicity of this system are apparent, though 
it can hardly be claimed that this is the most economical method of reheating 



lA^HM/J 



USE. 399 

compressed air. It is obvious that there must be the usual loss of heat units up 
the flue of the boiler, which should not take place in the same degree where re- 
heaters are employed which are specially designed for the purpose. We will be 
glad to hear from our readers in criticism and comment on Mr. Rix's system of 
reheating. What is very much needed in this line is a record of practical expe- 
rience. 

CALIFORNIA EXPLORATION LIMITED. 

San Andreas, Cal., June 8, 1898. 
Editor Compressed Air: 

I am just in receipt of the May-June number of your journal, and have 
read with much interest the article on Compressed Air Motors. I am particularly 
interested in what the writer says in regard to heating, since that is a matter of 
much importance with us, and I venture to ask if any facts were determined in 
these experiments which would bring into question the efficiency and desirability 
ofthe plan recently followed by E. A. Rix, at the Jupmper Mine, of passing the 
air through the steam dome, or above the water line, of an ordinary boiler. This 
plan seems to be satisfactory where a boiler is already installed. The consump- 
tion of fuel is low — about I/2 cord wood per 24 hours, for 100 H. P., and there 
would seem to be no reason to fear any of the difficulties due to passing the air 
through the hot water. W. L. Honnold. 



San Francisco, June 22, 1898. 
Editor Compressed Air: 

In any stationary boiler of a reasonable capacity there is no danger at all 
of the compressed air admitted to the boiler carrying water over into the engines, 
or in other words, priming the boiler. 

I failed to see any difference in the actions of the hoisting engine at the 
Jumper Mine, whether I introduced the air into the boiler through the blow off 
and mud drum or whether I introduced it in a pipe through the steam drum down 
to within about six inches of the surface of the water, but the action on the boiler 
was very marked. When I introduced the compressed air through the mud drum 
dnd allowed it to bubble up through water into the steam space, it vibrated the 
boiler to such an extent that I feared the setting of the boiler would be injured. 
In fact, if I had continued to run the plant another day 1 would probably have 
cracked one of the boiler walls, so I introduced the steam through the steam 
drum, and brought it down so that it impinged upon the surface of the water, 
and I noticed no different results as far as economy was concerned. 

The hoisting engine is a 75 H. P. hoist, having double 10x12 engines, 
hoisting from a depth of 700 feet, and handling sufficient ore, waste, men and 
timbers to operate a 20 stamp mill. The fuel used in reheating is eight cords per 
month of pine wood. 

As far as economy of reheating is concerned, dry reheaters give a greater 
economy than the wet reheaters — that is, if you take into consideration the fuel 
which the heater absorbs, but I generally advocate wet reheating, that is to say, 
using a steam boiler, especially if there is a boiler already installed, for if ex- 
cessive work should be thrown upon the compressor, or an accident should hap- 
pen to it, steam is already on the boiler, and it is only necessary to throw in ad- 
ditional fuel and the plant can be operated with steam. 



400 



USE. 



In general mining work I find that no matter how carefully a plant may 
be designed, there comes a time when it is necessary to shut it down, for a short 
period at least, to put in new brasses for the connecting rod to perhaps repair 
something which has been unavoidably broken, and it is at this time that the 
steam reheater pays for itself, and its perhaps inferior economy to dry reheating. 

Rix Engineering & Supply Co. 
Per E. A. Rix. 



Editor Compressed Air: March 9, 1898. 

In reading Compressed Air I have been much interested in the re-heating 
of air after it has been compressed to 80 lbs. or more; by different methods, par- 




FiG. 134. 



ticularly in the Sergeant Reheater, which seems to give such good results, the 
thought struck me that as electricity was used in connection with nearly every air 
compressing plant, and cars run by compressed air, for lighting, a reheater could 
be constructed by enclosing, in suitable form, coils of wire arranged to divide 
the incoming air into thin layers, and by the passage of electricity through the 
coils heating the air. 

Referring to the figures above, Fig. 134 is a sectional view of a reheater, 
cone shape, the inlet being at the right, the air entering is thoroughly cut up, if I 
may use that expression, and becoming heated, expands and passes out at the left. 
The other figure is an end view showing coils as they are arranged to divide the 
air. WM. F. towey. 

21 Emery Street, Medford Hillside, Mass. 



A NEW DEVICE FOR REHEATING COMPRESSED AIR FOR USE IN 

PUMPS. 

Too much attention has been given of late to the economical production of 
compressed air to the detriment of the economical use of compressed air in 
motors. As applied at present to the ordinary direct acting steam pump there is 
utilized only a fraction of its intrinsic energy, and many are the complaints 
directed against the economy of compressed air, on account of the very small 
returns which are made by these pumping devices. 



USE. 



401 



Of course the readiness with which an ordinary direct acting steam pump 
can be set up in a mine, and air turned into it, is the great reason for the num- 
bers which are in use to-day. In other words, the problem is one of utility rather 
than economy. An ordinary direct acting pump does not use air expansively, 
therefore but little can be expected from it, about 20 per cent, of the useful effort 
of the air being all that is converted into water pumped. 

In many places pumps of this character cause considerable annoyance from 
freezing, and for this reason compound direct acting pumps cannot be used with 
cold air. One can readily see that if the temperature of the exhaust of an ordi- 




FIG. 135 — PUMP REHEATING DEVICE TO INCREASE EFFICIENCY. 

nary direct acting steam pump is from 20 to 30 degrees below zero, which fre- 
quently causes stoppage from freezing, that to exhaust this low temperature of 
air in a compound cylinder and further reduce its temperature to perhaps 100 
would be an impossibility, because it could not work longer than the time which 
it took to reduce the temperature of its cylinder to the freezing point. 

A compound direct acting pump, which is heated sufficiently to prevent its 
freezing, will pump twice as much water for the same amount of air as a single 
acting pump. If a single acting pump will not freeze in working under ordinary 
conditions, introducing the air into the cylinder, we will say at 60 degrees tem- 
perature, the compound pump will not freeze if the air entering the compound 
cylinder be brought up to this same temperature. 



402 USE. 

If the ventilation in a mine is such that a reheater can be established under- 
ground, of course there is no difficulty whatever in running compound pumps, 
and very economically at that. There are some mines that do not object to carry- 
ing a steam pipe into the lower levels for the purpose of furnishing heat for the 
low pressure cylinder, but such opportunities are infrequent, inasmuch as the 
temperature of the mine is rais.ed to an undesirable point, and in carrying steam a 
long distance it becomes an expensive operation. 

A problem which occurred to the writer was to attempt to run plain com- 
pound pumps without any extraneous source of heat by utilizing simply the heat 
stored in the water being pumped at ordinary temperatures. The result was an 
installation of a Worthington pump having a capacity of 200 gallons per minute 
at a lift of 600 feet in the Gwin Mine, Calaveras County, California, 

The accompanying illustration, Fig. 135, shows approximately the manner 
in which the installation was made. A 300 horse-power Wainwright copper corru- 
gated heater was placed in the suction pipe of the pump, the water being pumped 
passing through the corrugated copper tubes at a temperature of from 60 to 70 
degrees. The air after being exhausted from the high pressure cylinder at a 
pressure of about 35 pounds, passes into the shell of this reheated and around the 
outside of the copper tubes. The extremely low temperature of the exhaust from 
the high pressure cylinder is thus neutralized by coming in contact with the 
water in the copper tubes, while the temperature of the air is raised to practically 
that of the water. It then passes to the compound cylinder, does its work and is 
exhausted without freezing. 

Before installing this compound pump on the 600-foot level of this mine a 
Worthington sinking pump had been used to pump out the water. The compressor 
furnishing the air to this pump made 55 revolutions to actuate it and to supply 
power for a hoist and to overcome pipe leakage, the latter two items taking about 
20 revolutions of the compressor, leaving 35 to be used for the pump. When 
the compound pump was put in place the revolutions of the compressor dropped 
down to 35, which showed a gain of 50 per cent, in favor of the compound propo- 
sition with its reheating. 

The work being done at this mine was to pump out an old shaft 1,500 feet 
deep, which had remained idle for about twenty-five years. The water was there- 
fore foul and inky in color and full of decomposed slates. This frequently coated 
the inside of the copper tubes and materially lessened their conductivity for the 
heat contained in the water, the result was that the pump froze up. After clean- 
ing the tubes, however, the pump operated as freely as before, showing con- 
clusively the advantage of the system. 

A still further gain would have been accomplished had the pumps been 
specially constructed for this character of work and the high and low pressure 
cylinders been water jacketed, permitting either the suction or the discharge water 
passing around the jackets and thus keeping them at an even temperature. 

This apparatus can be installed in the discharge pipe or in the tank adjacent 
to the pump where the water accumulates in the mine and can overflow it freely. 
Moreover, this is the proper manner of applying heat to air used in a compound 
pump. Many pumps have the air heated before it goes into the initial cylinder, 
which is economical as far as the initial cylinder is concerned, but by actual 



r^^rr^-':^^ 



USE. 403 

observations the writer has found that the clearances between the high and low 
pressure cylinder are such that the exhaust from the high pressure cylinder loses 
a considerable portion of its pressure before the stroke commences, and the drop 
in pressure causes such a drop in temperature of the air entrained between the 
two cylinders that the virtue of the reheating affects but slightly the compound 
cylinder where it is most needed. To be really an economical proposition the air 
should not only be heated before it 'goes into the high pressure cylinder, but in 
the receiver between the two cylinders and also in jackets around the two 
cylinders. There is no doubt that by doing this reheating properly in compound 
pumps where steam or highly reheated air is used, that the efficiency of this pump 
can still further be raised 25 per cent. 

If compressed air engineers desire to hold their own against the install- 
ments of electrical pumps they must employ more economical processes for pump- 
ing water, and pump builders can assist materially in constructing pumps properly 
for such work, and the above device will be found extremely economical and use- 
ful where heat cannot be safely introduced underground. — E. A. Rix. 



South Norwalk, Conn., Aug. 25, 1900. 
"CoMi'KESifEU Air:" 

Your July issue describes a Worthington pump with a re-heater device and 
refers to the apparatus as a novelty. 

This device was patented by me 19 years ago — U. S. Patent No. 244,603. 

The claims recite among other things: 

"First, the method of expanding or increasing the effective force or power 
of the air in a pumping engine driven by compressed air by utilizing the heat 
of the water acted upon by the pump as hereinbefore set forth. 

"Second, the combination of a compound air motor pumping engine and 
an interheater to be supplied with water from the pump as and for the purposes 
hereinbefore set forth." 

The device is good, but as you see from the above, not new. 

E. Hill, Gen. Manager, 

Norwalk Iron Works. 



Editor CoMrRESSED Air: 

I have a case where it is desired to reheat compressed air, to be used in a 
stationary automatic cut-off engine, consuming, perhaps, 300 to 450 cubic feet of 
free air per minute. We propose using oil burners of a small size and would like 
to know whether we can use a small-sized air re-heater, as the expense of a large 
size is rather too much. Can you give us any idea as to the number of heat units 
which will be necessary to raise the temperature of the air from 80 degs. to 375 
or 400 degs., so that, knowing the heat units in the crude oil, we can get a pretty 
good idea as to the amount of oil which will be consumed. Of course, in a 
common open re-heater all of the heat would not be effective. About what per 
cent, would you figure as effective? 

I would greatly appreciate your views at length on this matter. 

Wheeling, W. Va. practical. 



404 USE. - - - 

A large heater is required for this work. If you expect to heat the air to 
400 degs., you might use two reheaters or a series of reheaters, though, except 
in stationary plants, we do not advise reheaters of large sizes. 

Four hundred and fifty (450) cubic ft. free air per minute, to be raised 
from 80 degs. to 400 degs. F., 

^^r^34M lbs. X .2377 = 8.26 

heat units per degree rise in temperature ; 400 — 80=320 degs. required ; 320 x 3.26 
=2643 heat units per minute using oil^to 20,000 heat units per pound, say, de- 

2643 
ducting waste heat=i4,ooo heat units are available =.188 of a pound of 

14,000 

oil required per minute, 11.28 pounds per hour, or 112.8 pounds per day of 10 
hours, or about 16 gallons crude oil per day, at 3c., would be 48c. price to reheat 
450 cu. ft. of free air per minute from 80 degs. to 400 degs. 

The compressed air has slightly greater specific heat than free air, which 
may add a few cents to the cost while the efficiency will be increased by reheat- 
ing 44 per cent. 



REHEATING COMPRESSED AIR WITH STEAM. 

In the operation of motors by compressed air it is possible to bring about a 
considerable saving in the amount of air required in a given case by heating the 
air. 

This heating, or reheating as it is generally termed, may be accomplished 
in a variety of ways, generally by some form of furnace or combustion heater. 

In certain classes of work it becomes convenient to reheat the air with 
steam by either of the following methods : 

First. — A pipe from the boiler discharges steam into the air main and the 
mixture is carried into the cylinder of the motor. 

Second. — Air is passed through the boiler, either up through the water or* 
simply through the steam space over the surface of the water, and becomes mixed 
with and heated to the temperature of the steam. 

The accompanying tables show the results obtained with these two forms 
of reheating and will prove of value to those interested in the important problem 
of efficient reheating of compressed air. 

In calculating these tables one pound of air was assumed as the unit. The 
weight of steam to heat the air to any given temperature, and the final temperature 
after adiabatic expansion of the mixture to atmospheric pressure was determined. 
Then from the initial and final conditions of the mixture, and the properties of 
the adiabatic, the work of expansion and other desired relations were calculated. 

Dalton's law states that the pressures exerted by a mixture of gases or 
vapors is equal to the sum of the pressures exerted by the individual gases or 
vapors. Thus at 212" F. steam exerts a pressure of 14.7 lbs. per square inch 
absolute. A pound of air at 212° F., occupying 10 cubic feet, exerts a pressure of 
24.8 lbs. sq. in. absolute. 



USE. 405 

If this cubic foot tank is also saturated with steam at 212" F. the total pres- 
sure exerted will be the sum or 

14.7 + 24.8 = 49.5 lbs. sq. in. 

In the present problem steam is saturated and its pressure is found from 
its temperature in steam tables. 

The air pressure is found from the equation PV =^ RT, and the total pres- 
sure is the sum of the two, thus determined. 

The following notation will be used : 
n = pounds of steam mixed with one pound of air. 

Ps = pressure per sq. in. absolute, corresponding to temperature of steam. 
tj Q, Pi ^> 7. s, p, etc., the corresponding steam quantities as found in Peabody's 

"Tables of Properties of Saturated Steam," 
Pa = the "air pressure" lbs. sq. in. absolute in mixture, according to Dalton's 

Law. 
V = specific volume of air. 
R = gas constant. 
Po = initial air pressure in main. 
to = initial air temperature in main. 
C^ = specific heat at constant volume. 
Cp == specific heat at constant pressure. 
P = Pa -{• Ps=^ total pressure lbs. sq. in. absolute. 

Denote conditions after heating by subscript i, and after expansion by sub- 
script 2. 

STEAM DISCHARGED INTO AIR MAIN. 

Assume boiler and receiver pressures equal and neglect kinetic energy of 
motion. Suppose (w) pounds of steam separated by a circular diaphragm in the 
air main, from one pound of air, both air and steam being separated from the 
rest of the air by two sliding pistons. 

The volume occupied by the steam is ns; volume occupied by air is Vo; 
volume occupied by both air and steam is — ns+Vo. Remove the diaphragm, 
allowing steam and air to mix intimately, assuring finally a common temperature 
ti; the pistons moving out under constant pressure po, finally enclose a total vol- 
ume .vu The steam, of course, cools to a temperature ti, causing some condensa- 
tion. The final weight present, as steam, is nxu 

From the energy relations the loss of heat by mixture equals the work of 
expansion against pressure in air main. Hence, 



n (Q+p-qi—^iPi)—Co {t,—t^)=Ap {v,—v^—ns)\ A = -i- 

779 
RT RT^ nx, 

it, «= 5-: «) = -i— ; nSiX, = 

144^*0 ' 144 i'ai ' ' 3i 



and, pa i-\-p8 1 =Po. 



Making these substitutions and solving for n 
Q+p-{-J44^P8—qi 



4o6 



USE. 



With but a very small approximation, / — qx may be substituted for the 
denominator, and substituting numerical values we have finally, 



I 



1692(^1— ^0)+. 0683^0 



Po—P^ 



1 Po ' 



+ 



P9—VSI 



ADIABATIC EXPANSION OF THE MIXTURE. 

By adiabatic expansion is meant that no heat is given to or taken from the 
mixture although during expansion there may be a flow of heat between sleam and 
air. 

Since p=pa-{-ps, 

p dv=pa dv-\-ps dv. 
For an adiabatic dQ=o. 

dQ= Cv dt+n I dq-^d {xp) \ -\-Ap dv 
= Gv dt-{-Apa dv-^-n \ dq-\-d {3cp) [• 

-\-Aps dv=o. 

) 
^ - J" 

Cv 



But— 7? - dq-^d (xp) - -\-Aps dv may be reduced to, n -j dq-^2'd I^^A 
dt-\-Apa dv-j-n dq-\-n d U^\ T=o 



divide by T, 



Integrate, 



^ dt . . dv 

Cv ^ +Apa -^ 



ndq , . xr 



n 1 rr^PA ^^ Cndq 
Cv In T+S Apa -^ + '-^^ 



=K 



Then, 



f Apa dv 
T 


=AJR In V 


fndq 
T - 


"{^^n 


Cv loge T+AR lu v 


, nxr 

-\-nT+ ^, 


= Con's1. 


Alcr^ ^- 


BTy 


nxr 


BPP 



144 {p—ps) r ~ 144 ip—ps) 

MAKING NUMERICAL SUBSTITUTIONS AND APPLYING LIMITS. 
.5469 ?^5'l 0^1—- 1573 %10 {Pl—PSi)+ 

•3694 nrx^ 

Px—Pi» 

= .5469 log,oT^+--i573 %io (P2-PS2)+ 
.3694^2/3 



P2—P0S 



+wro. 



In this equation T^, p^, ps^, r^, } j, r^, p^ are generally known. 
T2 is unknown, as are the other quantities, which are direct functions of T». 
The equation can only be solved by the long and tedious method of trial and 
error and then only approximately. 



USE. 



407 



WORK DONE BY ADIABATIC EXPANSION OF THE MIXTURE. 

Proceeding by the usual thermodynamic method, draw an indicator diagram 
for an ideal engine expanding one pound of air and n pounds of steam to atmos- 
pheric pressure, and call this work W. 
In Fig. 136 let W=aTea. ahcf. 
W^i=area bcde ; 
f^2=area oa&?=i44 piv^.; 
f^3=area ofcd=^i44 P2V2. 
Then W=W,+ W,—Ws. 



TABLE 43 — REHEATING COMPRESSED AIR WITH STEAM. 

Results for Adiabatic Expansion of Mixture from 60 lbs. Gauge. 



i 

IS 
Si 

.2 ° 



f4 

li 

II 

1 


03 <U . 


1 

B 

a 
1 


2 
■5*5 

ill 


il 

"S'S 


1 



> 

-3 

a 


3 s 


on 




•s 

1 

w 



S3 

1 


g 

as 

c 


1 
so "^ 

CO 


.a Oh" 

« . 

.2S. 


SI 










(1h 







g e 


^ 




^ 


(^^ 


t^^ 


150 


.0515 


.365 


3.178 


1.23 


3 a. 4 


32.0 


12.5 


50,.50O. 


3.9 


92. 


34. 


7.96 


10.6 


170 


.0778 


.552 


3.390 


1.32 


29.5 


71.8 


13.7 


52,500. 


4.05 


78. 


39. 


10.4 


13.9 


190 


• .1175 


.801 


3.677 


1.43 


23.2 


101. 


15.1 


58,000. 


4.1 


63. 


54. 


11.5 


15.3 


210 


.1798 


1.275 


4.090 


1.59 


17.5 


124.6 


17. 


64,400. 


4.15t 


48. 


71. 


13.4 


17.8 


230 


.2818 


2.000 


4.733 


1.84 


12.5 


145.3 


19.6 


74,600. 


4.15t 


36. 


98. 


15. 


20.1 


250 


.4684 


3.3 >6 


5.855 


2.27 


8.4 


164. 


24.3 


93,300. 


4.1.5+ 


27. 


147. 


16.8 


22.4 


270 


.8741 


6.203 


8.242 


3.2 


5. 


181.5 


34.2 


122,800. 


4.14 


18. 


226. 


20.4 


27.2 



In the above it is assumed that Steam is fed to the air main by a separate pipe-boiler pressure 
and air pressure being CO lbs. gauge. 

CoudenHed Steam is supposed to be carried into the cylinder by the mixture. 

By Adiabatic Expansion is meant that no heat is given to or taken from the mixture. 

1 lb. air at 60* F., 60 lbs. gd. occupies 2.573 cu. ft. and gives 37,700 ft. lbs. with adiabatic 
expansion. 



a 




/T. 


A 






f*. 


f 




V 




— r 


y P^\o 


^ 


T^^ 


\ri 






- V > 






1 

1 



FIG. 136. 



Since the curve he is an adiabatic, W^. is equivalent to the loss of heat from 



h to c. 



4o8 



USE. 



The heat present at bi — heat present at ai equals Wu 

As shown above, a; = ; : ; also, v = -, Making these 

144 n{p—ps) 144 ip^ps). ^ 

substitutions, 



W, 



W, 



W. 



779 ) n {Qi- 
I44(j0i-J5sj' 



=)+ 



also, 



144 {Px- 
iPi—PHY 



■^cv ih—t^)- 



144 {p.2—pSs) 



(P2—PS2) 

Table 43 gives the approximate results of calculation from the above 
formulas, when both the boiler and air pressure are 60 lbs. gauge. Various initial 
temperatures are assumed to which the mixture is reheated, corresponding to 
which the weight of steam and other quantities are calculated. 

The increase of work due to reheating is the gain over the work of adia- 
batic expansion from 60° F. The rate of increase of work is given in pounds of 
steam per indicated horse power per hour; also the steam per brake horse power 
per hour assuming 25 per cent. loss. 



TABLE 44 — REHEATING COMPRESSED AIR WITH STEAM. 

Air is passed through a Steam Boiler and the Mixture works with Adiabatic 

Expansion. 






1: 

GO'S 


|.is 

|^& 
S X 







S 


^ 


ga 




Hi 


III 









P 


Hi 


II 
^1 



O. I 

? ^ • • 






RECEIVER PRESSURE 6o LBS. GAUGE. 



150° 


.03276 


32.° 


12.46 


3.92 


88.78 


47,480. 


25.9 


57.4 


21.9 


190° 


.09027 


99.75 


15.04 


4.09 


53.28 


57,740. 


53.2 


131.3 


19.5 


230° 


.24648 


144.8 


19.55 


4.13 


27.69 


74,440. 


97.4 


319.3 


14.8 


270° 


.83078 


181.4 


33.74 


4.09 


16.35 


130,670. 


246.1 


997.4 


12.0 



RECEIVER PRESSURE 100 LBS. GAUGE. 



150° 


.02095 




Final Temperature below 32° F. 






190° 


.05601 


53.83 


13.11 


5.74 


84.59 


66,740. 


55.4 


93.2 


33.8 


230° 


.14130 


116.4 


16.18 


5.96 


49.14 


80,630. 


87.8 


200.7 


24.2 


270° 


.37395 


157.4 


22.24 


5.97 


25.74 


106,460. 


147.9 


478.4 


17.1 



USE. 



409 



r"^ 
JIEHEATING BY PASSING AIR THROUGH A STEAM BOILER. 
In this case, the pressure in the boiler is also the receiver pressure and a 
pound of air is assumed to leave the boiler with « pounds of dry steam, both 
having the temperature of water in the boiler. 

The heat supplied by the boiler is in addition to that of the steam, th*; 
amount necessary to raise the temperature of and expand the air. 

Suppose air and water supplied to the boiler at the temperature to, while the 
boiler is maintained at the temperature h. The initial volume of one pound of air 
and n pounds of water is ^Jq+Wo cu. ft. The final volume at temperature ti be- 
comes Vi=nsi. Hence, the heat equivalent of external work becomes 144 Aps 

{Vt—Va—flQ.) 

Heat added to air = cv {h — h). 
Heat added to steam = n (^i+pi — go). 
Then the total heat supplied by boiler becomes, 
{B^T^ JJ^ per lb. of a\r)=cv («i— <o)+w (9i-+-;>i— ^o)+i44 ^Vo {v^—v^—nQ.) 
Substitute, 

PQ=pa^-\-ps^ \ 8-0— w. 
144 ApiD=ART ; and neglecting p^^no, 

-^AR (r,-ro)+i44 Aps^v^. 

Since, Cv-\-AR=Cp, specific heat at constant pressure,— 52' CT becomes, 

B^Ti Ui=cp (<i— <o)+^ ('^'i — 9o)-\-^44P^iA.Vo and when ^0=60° F., 

B,2\U,=.2375 (<i— 6o)+7i(;ii-28.i)+.4662^Si. 

The weight of steam per pound of air is calculated from the formulae : 



H4(Pi—pSi) 



TABLE 45. 



T 


A 


B 


C 


150*^ 


27.8 


21.9 




170" 


21.3 






190° 


19.2 


19.5 


32.8 


210° 


16.5 






230° 


14.7 


14.8 


24.2 


350° 


13.2 






270° 


10.8 


12.0 


17.1 



T. — Initial Temperature of Mixture. 

A.— Thermodynamic Efficiency of Reheating Steam fed in pipe near motor. 

B.— When passed through boiler at 60 lbs. gauge. 

C— When papsed through boiler at lOD lbs. jfauge. 



4IO USE. 

The final temperature and work of expansion are calculated by the general 
formula given above. 

The thermodynamic efficiency of reheating is the ratio of the heat equivalent 
of increased work to the heat added. 

Table 44 gives the approximate results of calculation for this method of 
reheating. 

Air and water are both assumed to have a temperature of 60° F. before 
heating. 

Table 45 shows the relative merits of the two systems, both being on the 
basis of 60" temperature of feed, air and water. 

It is interesting to note that the efficiency of dry reheating is 38% at 60 lbs. 
gauge, and 45% at 100 lbs., gauge, with adiabatic expansion, 

Clarence R. Weymouth. 



ELECTRIC AIR HEATING. 



It is perfectly practicable to heat compressed air before it passes into the 
motor cylinders, by means of electric currents, and that without the slightest 
danger. It may be done either by forming a resistance coil in the usual way, in 
the path of the air, or by wrapping the pipe with a conductor through which a 
current of electricity is allowed to pass. The conductor must in each case be 
allowed to attain a fairly high temperature, but it need not be exposed, nor need 
the temperature be such as to be dangerous, in case of the presence of an 
explosive gaseous mixture. 



EXPERIMENTS ON THE REHEATING OF COMPRESSED AIR.* 



By William George Walker, A. M. I. C. E., M. I. M. E. 

Mr. Patrick Y. Alexander, of Experimental Works, Bath, and the author, 
have during the past few months, at Chiswick and elsewhere, carried out some 
experiments on the reheating of compressed air. Considerable economy can be 
obtained by reheating compressed air before admitting it to the engine. Reheat- 
ing is accomplished by two methods: — (i) By passing the air through hot 
pipes heated by a furnace fire. (2) By passing the compressed air through 
water in a boiler at a temperature depending on the pressure in the boiler. The 
former is called the dry method and the latter the wet or moist method of heat- 
ing. It has long been the custom in Paris to use a small stove, through which 
the compressed air is passed before being used in the motor. Prof. Unwin, 
F. R. S., states that "Prof. Riedler tried an old 80 horse-power steam engine in 
Paris which had been adapted to work as an air motor, and which was actually 
giving ^^2 indicated horse-power with compressed air at 5^ atmospheres. It 
was using about 31,000 cubic feet — reckoned at atmospheric pressure — or about 



* British Association, Bradford, Section G. 



USE. 411 

^376 lbs. of air per hour. This air was heated to a temperature of about 300 deg. 
Fah. by the expenditure of only 15 lbs. of coke per hour. On a favorable assump- 
tion a steam engine working to the same power would have required ten times 
this consumption of fuel at least." Prof. Unwin also says that reheating has the 
practical advantage of raising the temperature of exhaust of the motor, and for 
the amount of heat supplied the economy in the weight of air used is surprising. 
"The reason of this is that the heat supplied to the air is used nearly five times 
as efficiently as an equal amount of heat employed in generating steam." The 
author and Mr. Patrick Y. Alexander have, during the past few months, carried 
out a number of experiments on the reheating of compressed air by the wet 
method, i. e., by forcing compressed air into a boiler containing water, when 
very economical results were obtained. 

Last year Prof. J. T. Nicolson, D. Sc, M. I. C. E., carried out some very 
valuable experiments in Canada under the auspices of the Taylor Hydraulic Air 
Compressing Company. Prof. Nicolson experimented with five different methods 
of using compressed air in an ordinary steam engine of the Corliss type of about 
27 indicated horse-power, (i) The air was supplied to the engine cold. (2) 
Steam was injected into the air in the main pipe before supplying ,it to the 
engine. (3) The air was injected amongst the water in the steam boiler and 
heated by mixing with the water and steam of the boiler before being supplied 
to the engine. (4) The air was blown upon the surface of the water in a 
steam boiler and heated by mixing with steam in the same, before being used to 
drive the engine. (5) The air was passed through a tubular heating vessel 
and heated by a coke fire, afterwards being used to work the engine. The com- 
pressed air was drawn at a pressure of 53 lbs. from the 6-in. main air pipe of the 
Taylor air compressor. The author gave an account of this compressor at the 
Bristol meeting of the British Association, 1898. The wet heating was carried 
out in a Lancashire boiler 7 ft. diameter by 30 ft. long. 

Experiments were first made without reheating, when about 850 cubic feet 
of free air were used per indicated horse-power per hour. The air was then 
heated to 287 deg. Fah., by passing the compressed air through pipes heated by 
coke, under which condition 640 cubic feet of free air was used per indicated 
horse-power per hour, being a reduction of 210 cubic feet of free air per indicated 
horse-power per hour, due to reheating. Thus a saving of 25 per cent, is effected 
in the quantity of air used. This saving was effected by the burning of 348 lbs. 
per horse-power hour. The results may be stated as follows: — 100 horse power 
in cold compressed air was raised to 153 horse-power when reheated to a tem- 
perature of 287 deg. Feh. by an expenditure of 47 lbs. of coke per hour, or at the 
rate of 1.42 lbs. of coke per horse-power per hour additional. This is equivalent 
to an additional horse-power for every pound of coal burnt in the heater, which 
is far more economical than the most efficient steam engine and boiler. By 
mixing from 10 to 15 lbs. of steam per horse-power with the air, the quantity of 
air required was reduced from 850 cubic feet to 300 to 500 cubic feet per indicated 
horse-power per hour. The results showed that the extra horse-power due to 
heating by the wet method was obtained at an expenditure of 1.3 lbs. of coal per 
additional indicated horse-power per hour. 



412 USE. 

The author's own investigations are most 'conclusive as to the efficiency 
of reheating, either by the dry or wet method. Generally speaking, the results 
show that an additional horse-power can be obtained with an expenditure of i lb. 
of coal. Better results even than this have been obtained, which is far more 
economical than the most efficient engine and boiler using steam ever produced. 
And the experiments seem to show that in many cases it would prove advan- 
tageous to use compressed air in conjunction with steam in an ordinary engine. — 
The Engineer, London. 



THE AIR BRAKE. 



As early as 1852 a patent was granted in this country for an alleged inven- 
tion of a railway brake operated by steam, and a few years later patents were 
issued in England for alleged air-brakes, but the first practical air-brake was not 
produced until about 1869, when George Westinghouse, Jr., of this country, in- 
vented what was then known as the "plain-brake." This consisted of a pump 
operated by steam from the locomotive boiler, which compressed air into a reser- 
voir located under the locomotive cab. This was under the control of the engi- 
neer by a valve in a pipe leading from the reservoir. From this valve a pipe ex- 
tended under the tender and was connected by flexible hose sections to a similar 
pipe under the entire length of each car. Branch pipes led to "brake-cylinders," 
and the stems of the pistons in the latter were connected with the brake-levers 
on the cars. Upon opening the engineer's valve, air pressure passed to these 
cylinders, pushing the pistons backward, operating the brake-levers and forcing 
the brake-shoes against the wheels. It was found that the operation of this 
apparatus was too slow, and was attended by danger of collision in case one part 
of the train became detached. 

About 1872 or '73 Westinghouse produced an "automatic brake" which 
embodied the addition of an auxiliary reservoir and a triple-valve device to each 
car. Each reservoir was of sufficient capacity for at least one full application of 
the brakes, thus providing for automatic action in the event of accident. The 
operation of this brake was radically different from that of the "plain-brake." 
In the former the compressed air was stored in the main reservoir until re- 
quired for the application of brakes; in the latter the main and auxiliary reser- 
voirs and trainpipe were always charged with compressed air at working pres- 
sure, to prevent the application of the brakes. The former system was operated 
by pressure from the main reservoir, while the latter system was operated by re- 
duction of pressure in the train pipe. The result was automatic in action in case 
of accident, such as the bursting of hose or the train breaking in two. But this 
"automatic brake" was not capable of successful operation on long trains of 
freight cars. It was publicly tested in 1886, near Burlington, Iowa. 

In 1885 the Railway Master Car-Builders' Association arranged for a 
series of experiments. Several companies entered into the competition, but none 
succeeded in stopping long trains of freight cars without violent and disastrous 
shocks. The trials were renewed in 1887, with five competing companies. The 
report of the committee was against all the competing devices, the committee 



USE. 413 

concluding that air-brakes actuated by electricity were the only ones likely to be 
capable of successful operation on long trains of freight cars. 

After these trials Mr. Westinghouse set himself to work to obviate the 
difficulties that had not yet been overcome, namely, to provide for uniformity in 
the application of the brakes and preventing shocks to the cars. 

In the latter part of 1887 he succeeded in constructing a quick-action auto- 
matic brake, capable of being successfully applied to a train of 50 cars, and 
operative under all conditions of practical railway service. The requirements 
with which he then for the first time successfully complied were: (i) The regu- 
lation of the force to be applied to th^ brake-shoes so as to secure all necessary 
graduations, from the mere slackening of speed to the service-stop, and from 
the service-stop to the emergency-stop. (2) The automatic operation of the 
brakes in case of accident. (3) The practical simultaneous operation of the 
brakes on each car, so that, in long trains of freight cars, shocks might be 
avoided. (4) The control of all these operations by the engineer; and (5) Cer- 
tainty of operation under all conditions. 

This has been judicially determined to be "the first system which practi- 
cally solved the problem of immediate stoppage of a long freight train in time 
of danger, in connection with and supplemental to "train-brake graduations." 

Less than ten years ago this matter was still problematical. To-day nearly 
every railroad in the United States and Europe is equipped with brakes operated 
by compressed air. 



AIR BRAKE SERVICE. 



The air brake is one of the applications of compressed air that has made a 
permanent place in its own field, and its development brings out some interesting 
facts in connection with train service. 

During the three years that the high-speed brake has been in service on the 
Empire State Express not a single case of slid fliat wheels has been reported. 
From 1886 to 1896 the distance required to bring a passenger train to a stop has 
been reduced one-half. This is due to the use of the high-speed brake instead 
of the plain automatic brake. The distance in which a train can be stopped from 
a speed of 40 miles is nearly twice as great as that from which it can be stopped 
from a speed of 30 miles an hour. To stop a train going at the rate of 50 miles 
an hour, the stopping distance is three times as great as that required at 40 miles 
an hour. At 60 miles an hour the distance required for stopping is about five 
times as great as that required for 30 miles an hour, and more than two and one- 
half times as great as that required at 40 miles per hour. 



THE AUTOMATIC AIR BRAKE. 

The Automatic Air Brake has been in service for so many years, and has 
been so faithful and punctual in performing the offices required of it, that we 
have come to look upon its prompt and efficient action as a matter which is of 



4T4 USE. 

course to be expected. A little reflection upon the conditions under which it 
operates, however, will bring the conclusion that the certainty and reliability 
with which the automatic brake performs its work is one of the most remark- 
able characteristics of the apparatus. 

In the first place, the orderly performance of the different operations of 
the automatic brake is entirely dependent upon the operation of a piece of 
mechanism called the triple valve, which requires unusual nicety of construction, 
and which, in some respects, requires the most careful adjustment. This valve 
mechanism consists of a number of moving parts, which must operate every time 
the brakes are applied, and every time that the brakes are released. The delicacy of 
the adjustments would appear to require careful watchfulness, considerate atten- 
tion and reasonable protection. Yet this apparatus is secured beneath the floor 
of a railroad car which goes jolting over the road, is subject to constant vibra- 
tion and concussion, and is subjected to the influence of a constant whirl of cin- 
ders, sand and dirt. These conditions are of themselves such as would seem 
to prohibit the successful use of a delicate piece of mechanism to be operated by 
small differences of air pressure. More than this, the neglect to clean and lubn 
cate the frequently moving parts of this delicate mechanism has in many in 
stances extended over years at a time, so that it would most naturally be ex- 
pected that it would become so disordered as to entirely refuse to operate. Yet 
it has gone on, year after year, under these most trying conditions, performing 
the service required of it with promptness and efficiency to an extent that seemed 
to indicate to some that it really was unnecessary to give the apparatus any at- 
tention at all. 

The continued reliability of the apparatus must be attributed, first of all, 
to unusual care in the selection of material, and to methods of special accuracy 
and refinement in manufacture. The prompt release of the brake depends, to a 
large extent, upon such a high character of material and workmanship, because 
the operation of the triple valves to release the brakes depends upon a small ex- 
cess of air pressure upon one side of a small piston, which excess can be ob- 
tained but gradually, and would be impossible to obtain at all if any material 
leakage past the small piston occurs. 

But the complete reliability of the apparatus for the application of the 
brakes is a feature of design and invention. The brakes are applied by dissipat- 
ing the air pressure in the main air pipe which extends throughout the train, 
and, however much difficulty there might be in charging an efficient pressure 
into the pipe, there can never be any doubt of the ability to promptly discharge 
the air pressure, as it merely requires an opening from the pipe to the atmosphere 
at any point. In this way a powerful pressure upon one face of the small piston 
of the triple valve may always be promptly rendered available for moving the 
piston into a position to apply the brakes. 

Any uncertainties, therefore, as to the operation of the automatic air 
brake, which may arise from neglect and disorder, apply only to the release 
of the brakes, whereby the train may be enabled to proceed; but, once that the 
brakes are released and charged with air pressure, the prompt response of the 
apparatus to apply the brakes, at any time that they may be required, is assured 
and inevitable, as the only requirement then is that the train pipe shall be given 
an opening to the atmosphere. 



USE. 415 

QUICK-ACTION AUTOMATIC BRAKE. 

The April issue of Compressed Air contained a brief resume of the his- 
tory of the air-brake down to the completion of the present quick-action auto- 
matic brake, which has successfully stood the test of time and use and demon- 
strated beyond peradventure its superiority over all other brakes known and 
tried. 

In the quick-action automatic brake the application of the brakes to the 
v/heels is effected by reducing or cutting off the air pressure in the main train 
pipe leading from the main air reservoir. This reservoir is carried beneath the 
engine and is charged with air from a pump also on the engine, the pump being 
operated by steam from the boiler. The "engineer's brake and equalizing dis- 
charge valve" is located in the cab of the engine and is connected to a pipe leading 
from the main reservoir and a second pipe communicating with the train-pipe. 
This valve regulates the flow of air from the main reservoir into the train pipe 
for releasing the brakes, and from the main train or brake pipe to the atmos- 
phere for applying the brakes. The main train pipe leads beneath all the cars of a 
train, being connected between the cars by flexible hose coupled to the pipe sec- 
tions. By means of an anglecock at each end of the pipe of each car, such pipe is 
closed before separating the couplings, thus preventing the escape of air and the 
application of the brakes when the cars are uncoupled. 

Beneath each car is an auxiliary reservoir which takes a supply of air from 
the main reservoir, through the train pipe, and stores it for use on its own car. 
The brake cylinder is connected to this auxiliary reservoir, and its piston rod is 
attached to the brake levers in such a manner that, when the piston is forced 
out by the air pressure, the brakes are applied. The quick-action automatic 
triple valve is connected to the main train pipe, auxiliary reservoir and brake 
cylinder, and is operated by the variation of pressure in the pipe — first, so as to 
admit air from the auxiliary reservoir to the brake cylinder, which applies the 
brakes, at the same time cutting off communication from the brake pipe to the 
auxiliary reservoir, or, second, to restore the supply from the train pipe to the 
auxiliary reservoir, at the same time letting the air in the brake cylinder escape, 
which releases the brakes. A pump-governor regulates the supply of steam to 
the pump, stopping it when the maximum air pressure desired has been accu- 
mulated in the train pipe and reservoir. 

In practice, a moderate reduction of air pressure in the train pipe causes 
the greater pressure remaining stored in the auxiliary reservoir of each car to 
force the piston of the triple-valve and its slide-valve to a position which will 
allow the air in the auxiliary reservoir to pass directly into the brake cylinder 
and apply the brakes. In the event of emergency or accident, a sudden reduction 
wil be had in the train-pipe, producing the same effect, and in addition to this, 
causes supplemental valves in the triple-valve to be opened, permitting the pres- 
sure in the train pipe to also enter the brake cylinders, increasing the pressure 
from the auxiliary reservoir about 20 per cent., resulting in instantaneous action 
of the brakes to their highest efficiency throughout the entire train. Hence, in 
case of accident, real or threatened, a train can be brought to an immediate 
stop. When the pressure in the train pipe is again restored to an amount in ex- 



4i6 USE. 

cess of that remaining in the auxiliary reservoir, the piston and slide valve are 
forced in the opposite direction, opening communication from the train pipe to 
the auxiliary reservoir, and permitting the air in the brake cylinder to escape to 
the atmosphere, thus releasing the brakes. When the engineer wishes to apply 
the brakes he operates the "engineer's brake valve," so as to close one port, re- 
taining the pressure in the main reservoir, and then permits a portion of the air 
in the train pipe to escape, reducing the pressure therein and allowing the greater 
pressure in the auxiliary reservoirs to be brought into action on the brakes through 
the agency of the triple valve. To release the brakes he so turns the valve as to allow 
the air in the main reservoir to flow freely into the train pipe, restoring the pres- 
sure therein to a degree greater than that in the auxiliary reservoirs. 

A valve in each car, called the "conductor's valve," is capable of operation 
by any of the train men in the event of emergency. By pulling on the cord of 
this valve the latter will be opened and allow the air in the train pipe to escape. 
Should any of the cars of a train become accidentally disconnected, the air in the 
train pipe escapes and the brakes are instantaneously applied in each section of 
the train. They are likewise applied in the event of a pipe bursting. Hence, 
the underlying principle is that any reduction of pressure in the train pipe ap- 
plies the brakes to the wheels. 



AUTOMATIC OR DIRECT AIR-BRAKES FOR STREET RAILWAYS. 

With the advent of heavy cars of the double truck type, air brakes are com- 
ing into very general favor, but on roads operating with trail cars they have for a 
long time past been very successfully used. In this latter case, particularly where 
the cars run over grades of any moment, some engineers contend that the so- 
called automatic system, such as is in very general use on steam railroads, should 
be applied to street railways, even where but one trail car is used. As in this 
system the breaking away of the trail car automatically applies the brake, it is 
quite natural that engineers should advocate its use, but a close study of the 
question will show that the conditions of service on street and steam railways are 
very different, and what is an excellent device on the latter has many serious 
drawbacks when used on the former in trains of two or three cars. 

In the direct air system the pressure stored in the main reservoir is 
admitted directly to the brake cylinder pipe, the application of the 
brakes on a two or three car train being practically instantaneous when 
we open wide the valve on the motor car connecting this pipe to the 
reservoir. Now if we also run a pipe from the main reservoir, on the motor car, 
through to a reservoir on the trailer, and on the latter put a cock between the 
reservoir and train pipes, the conductor by opening it can apply the brakes, in 
case of necessity, as well as it is done in the automatic system. Again, if the 
couplings between the cars are provided with check valves which are pressed 
open when the two halves are connected, and close instantly when pulled apart, 
should a trailer break away from its motor car, it will have a supply of air at main 
reservoir pressure in its own reservoir, and the conductor, upon feeling his car 



USE. 

take a retrograde movement, can open his valve and apply the brakes. This val* : 
may be operated by a cord running the length of the car; so he has only to raise 
his hand to put on the full power of the brake, and this device is all that would be 
necessary on 99 roads in a hundred. If, however, an automatic device is insisted 
upon, as it might be in the one hundredth case, another cock, placed at the end of 
the trail car, with its handle connected by a chain to the motor car, would be 
opened upon the breaking off of the trailer, and apply the brakes as quickly as 
the "automatic air" system. 

Therefore, it should be a simple matter for a street railway manager to 
decide whether or not he will equip his cars with a device which takes the dir-.^f 
control of his power brake out of the motorman's hands, and thereby jeopardizes 
every one of about a million stops, for the sake of moving by air a valve that will 
automatically apply the brakes in case of the trailer breaking away, when equally 
safe results may be obtained by a valve operated by the conductor or mechan- 
ically, but which leaves the operation of the brake directly in the hands of the 
motorman, thereby making it absolutely certain to act when he moves his hand, 
to say nothing of the smoother and better service thereby obtained. 

Furthermore, the improved automatic couplers and heavy safety chains used 
to-day reduce to a minimum the liability of a trailer breaking away from its 
train, and thus, for this class of service, rob the automatic system of its peculiar 
charm. In view of the magnificent service performed by the automatic system on 
steam railroads, no one could deny its value in this field, but on street railways 
it is a "white elephant," pretty in theory, but bad in practice. 
' , E. H. Dewson. 



rESTS OF STREET CAR BRAKES BY THE NEW YORK RAILROAD 

COMMISSION. 

The most important and exhaustive series of tests of street car brakes 
ever undertaken was made last year by the New York Railroad Commission; 
and their results have just been made public in a pamphlet of 60 pages, accoir. 
panied by plates showing the autographic records taken during the tests. Copie 
of this pamphlet can be obtained, we presume, by addressing the office of the 
New York Railroad Commission at Albany. In the present article we shall 
c attempt to summarize the main results reached by these tests, and the most im- 
' portant lessons to be drawn from them. 

These tests, which were briefly described in this journal while they were 

t made on the Lenox avenue line of the Metropolitan Street Ry. Co. in New York 

l City. The track chosen for the test has a very slight grade (8.8 ft. per mile), 

lid is laid with 90-lb. girder rails with 2-in. head. The line is a double track 

one, operated by the electric underground conduit system. The cars used were 

the Metropolitan company's standard 8-wheel cars, weighing 20,816 lbs., equipped 

' with Brill "maximurii traction" trucks, with 30-in. and 20-in. wheels, and a tot.-'l 

wheel-base of 17 ft. 6 ins. Brake shoes were applied to all wheels. 

There were 26 applications by brake manufacturers and inventors to take 
put in the tests; and 16 companies actually equipped cars and had tlieir apparatus 



USE. 

, ed. Of these, 4 were air brakes, 4 electric, 3 hand-power, 2 friction, and 2 were 
rombined track and wheel brakes. The different brakes are described as follows| 
ii; the official report: 

AIR BRAKES. 

The reliability of the air brake has been thoroughly established by its use 

on steam roads. A large number of them are now used on electric cars, and 

with proper inspection and care, the air brake, as applied to electric cars, is a 

liable, powerful, quick and easily controlled means of applying the braking 

■^wer to a car wheel. Four systems of air brakes were submitted and tested 

Ml were similar, so far as relates to the use of air under compression in a cylinder 

. to operate a piston from which, through levers, the power was transmitted to th( 

ijr ike shoes. They differed in the method of compressing the air and applying i 

rr the piston. 

The G. P. Magann Air Brake Co. presented what is known as a storag 
rnr system, in which there is an air compressor and reservoir located at the 
I'ower-house or some central point on the street car system. This reservoir i 
cinrged with air usually compressed to 300 lbs. pressure. The car is equipped 
with two storage reservoirs, which are charged in a few seconds from the sta 
tionary reservoir at 300 lbs. pressure. By means of a reducing valve this pres^ 
-nre is reduced to 50 lbs., at which pressure the air enters an auxiliary reservoir 
from which it is controlled, to the brake cylinder by means of the engineer': 
valve, in the usual- manner. There are some special features in the constructioi 
and operation of this valve. The storage equipment of cars is calculated fc 
300 stops, which is sufficient for ordinary car operation ; when necessary th 
capacity can be increased. 

The Christensen Engineering Co. presented what is known as the straighi 
air system, which consists of a reservoir, an electric motor compressor, an au 
matic regulator which governs the operation of the motor compressor; an en,l 
reer's valve and the usual brake cylinder. In this system, as its name imp-.es 
tl:e compressed air passes direct from the reservoir to the brake cylinder, t\er 
being no auxiliary reservoirs or reducing valves between the pressure reservoi 
:id the brake cylinder. All of this apparatus, with the exception of the :oi 
oiler, is placed under the car. There are a number of special features in tl 
.. nstructlon and operation of the system as presented by this company 

The Standard Air Brake Co. presented an automatic air brake system, coi 
.i sting of an electric motor-driven compressor, a storage-pressure reservoir, 
motor controller, brake cylinder and engineer's valve. This system is simil' 
to the one described above, except that there are a number of special features 
construction and operation in which the two systems differ ; the general princip 
of compressing and applying the air is, however, the same. 

John E. Reyburn presented an air brake system similar to the 
described, except that the compressor was operated mechanically instead 
• ic^ctric motor. This compressor was worked by the motion of the car ax, 
^^ hich was transferred to the compressor by means of friction discs, or whee, i 
one of which revolved with the axle, the other being fast on the compressor sha \ 
These were placed in such position that they made a firm frictional conta^ ' 
These friction discs are thrown into contact and released by compressed i 

I 



two Itl 
of by 1 ' 



USE. 



419 



the reservoir. After the air has been compressed in the cylinder, the opera- 
is the same as usual in air brake systtms.— Engineering News. 



' .N INDEPENDENT MOTOR TO UTILIZE THE BRAKE ENERGY. 

In a lecture before the Board of Trade of the City of Worcester, Mass., Mr. 
rrill E. Clark, who has invented various ingenious machines, introduced and 
.scribed a system of independent motor and a means of utilizing the brake 
ff.rgy in connection with street railway and other traction. 

' ;He described it as a self-contained, independent motor; one where it was 
It necessary to return to a storage station at short intervals, as is necessary with 




FIG. 137 — EXPERIMENTAL AIR MOTOR. 



the high pressure systems. In this system the air is compressed to the workuig 
pressure only. 

"In connection with this independent system is another source of economy. 

a direct gift, if so it may be called. This source is from the compressor brake. 

an arrangement whereby air compressors are operatively connected with the axles 

of the truck, in such a manner that when the car is retarded or stopped, the 

; -y ordinarily lost in the application of a brake is used to operate the air com- 

or and the air stored for subsequent use. As it requires about three times the 

or to start than it does in the general run, the immediate use of tlic air just 

•d by simply moving a lever is very desirable. Thus we have at our disposal 



420 



USE. 



for useful work the entire momentum of car or train less the friction, wher 
\ve wish to reduce its speed. 

The majority of motor vehicles are propelled from the axle. Why not . 
them from the same point? 

That energy due to the moving car or train, is not only available, but v 
able, is illustrated by an estimate made at the Polytechnic Institute, April 2 
1896, in which it was shown that the work required to stop a train weighing 
424,000 pounds, in twice its length., say 800 feet, from a speed of one mile a min- 
\\as 4,665 H. P. applied constantly during a period of 20 seconds, or 1,555 H. 
for one minute. Illustrations of this problem can be seen daily. The eleva« 
reads in New York and Chicago are good illustrations, where the trains run abc 
one-third of the time on the brake, drawing from the boiler or electric supply 




FIG. 138 MOTOR OI'ERATIXG BAND SAW. 

apply them. Suppose these conditions were reversed and energy stored during the 
same time. The cost of operating would be materially reducd. 

In the introduction of the combination air compressor, the brake com- I 
pressor finds its largest development, whatever heat is lacking, due to intermittent 
operation of the brake, is supplied from the exhaust of the impulse cylinder 

In the ordinary oil or gas engine quite an amount of heat escapes through 
the exhaust, but in the compressor system the largest proportion of heat is 
utilized. The heat from the impact cylinder supplying the motor requirements, 
and the cold produced by the motors, is turned back to do service at the combus- 
tion cylinders. Thus the exhaust is both utilized and muffled. As an illustra- 
tion of this, it is shown that the exhaust from air motors in Paris, is used for 
refrigerating purposes and the exhaust from gas engines in Pittsburg is used for 
heating purposes. 

To harness an external combustion engine direct to the axle of a car or 
locomotive offers difficulties at once, an impact sufficient to start from a point of 



r^ 



USE. 



421 



Ad wreck the machinery. We can secure the energy, but the natural 

f the pistons would be many times faster than the speed of the crank pin 

"mpire State express engine running at its best. 

ih'' -ni»bustion compressor here advocated is so constructed that a very 

jrm pressure is maintained between the combustion and air cylinders, the 

It of which secures to this system, not only the highest attainment of the 

in engine, but reduces impact to pressure, in the most efficient form. For 

n the predetermined working air pressure is reached, the supply of fuel is cut 

and the machine stops, not simply runs idle, which occasions waste to a con- 





N'ERRILL E. CLARK. In 



FIG. 139 — THE INDEPENnENT MOTOR SYSTEM. 



' rable extent and when the pressure falls below the desired point, the compres- 
; automatically starts, restores and maintains the said working pressure. 

In this way all waste from the safety valves with its attendant disagreeable 
se is avoided. 

It will be noticed that in this system the fire-box, flue system, cinder cham- 
and smoke stack are dispensed with and locomotives in use at the present time 
.1 be readily equipped with this system, at comparatively small expense. 

What is here said of the locomotive is applicable to the steamship, where 
this system can be used with great efficiency and economy. 



4^2 USE. 

When we consider the force developed in the internal combustion cylinder 
at small expense, and know that this power can be greatly increased, when the 
mechanism is favorable to transmit it with safety, that compressed air possesses 
the advantage of steam, from maximum pressure, to multiplied expansion, with a 
balance in its favor. We look to see in the near future the perfected motors not 
only on our streets but making the longer journeys on land and sea. Not only 
with the speed of the wind, but with the annoying smoke and cinders eliminated. 

At this writing, we are not prepared to publish the details of construction 
of the motor and other apparatus, owing to the preliminary work. 

We will say, however, that this motor consists of a plurality of internal 
combustion and air cylinders with their axis in alignment for the purpose of 
reducing friction to the minimum point. 

These several cylinders are arranged to develop the highest power in t^e 
combustion cylinder to correspond to the highest performance of the air cylinder, 
thus creating a practically perfect and uniform power during a whole revolution. 

This point is certainly worthy of consideration in street railway practice, 
where shocks or vibrations are to be avoided." 



AIR CARS. 

The late Franklin Leonard Pope, a distinguished. electrician, said that if 
but a fractional part of the money and brains that have been spent upon the 
development of electricity as a motive power for street railroads had been spent 
upon compressed air, we would now be riding on pneumatic tramways. This 
is a statement worthy of serious consideration. Prof. Hutton of Columbia 
College, recently repeated it, quoting Mr. Pope's words, and expressing his own 
belief that compressed air offers much encouragement to experimenters in this 
line. The extensive development of the trolley is the result of brains, energy 
and money, which in all things is sure to win in the end. Nobody now doubts 
that electricity is well adapted for tramway work, nor does any unbiased person 
question the fact that the trolley, under certain conditions, is the best means of 
street car propulsion. But there are some places, and certain conditions, where 
the trolley either should not be used because of objectionable features,, or, when 
used, it does not accomplish the result in the most economical manner. This is 
the field for the compressed air motor. 

It is well known among engineers that it is not economical to distribute 
power electrically unless that power is consumed as fast as it is produced. In 
other words, a dynamo developing, say, 50 h. p. and distributing it for power 
purposes, is not economical unless the motors consume the maximum available 
power at all times. If we have a short line of street cars, say one mile in length, 
as for instance a means of transporting passengers between a railway station and 
some other point, and desire to equip this line with a motive power other than 
horses, it is not likely that it would pay to equip with the trolley, because with 
one or two cars on the line running at infrequent intervals, there would be 
times when no part of the power generated at the central station would be re- 
quired at the car, because there would be no car in motion; hence it would be- 



USE. 423 

)me necessary to either stop the engine which runs the djmamo, or to provide 
some other means of utilizing the electric current. Such a road as this calls for 
a storage system, and the best power for a storage system is compressed air. 

There can scarcely be any doubt about the fact that there is a field for the 
storage system of street car propulsion, because so much time and money has 
been spent in efforts to perfect the storage battery. It is equally as clear that the 
electric storage battery system is a failure up to date. Whatever other reasons 
there may be for this, the principal difficulty is in the battery itself. This being 
the case, is it not surprising that some of this time and money is not spent upon 
some power other than electricity as a storage power? Compressed air is par- 
ticularly well suited for this purpose. Nor is it a matter which involves much 
doubt as to the practicability of compressed air as a power for propelling cars by 
the storage system. It is almost entirely a question of availability for specific 
purposes, of adaptability for tramway service; and in order to reach this point, 
experiments involving time, invention and money are of course necessary. The 
pneumatic locomotive, which has been built, and which is now used largely in 
mines and elsewhere, is an evidence of the practicability of compressed air as a 
tractive power. Some of the locomotives are of large size, others are small, and 
many of them have about the same power capacity as that required for street 
car propulsion. These locomotives store air at pressures varying from 400 to 
2,000 pounds pressure per square inch. Many of them do not reheat the air at 
all before use, and yet we venture to say that it would be a serious matter if 
those now using them should be called upon to stop, as we doubt that any power 
would be as useful, or in most cases as economical. 

To store compressed air and use it as a power is a very simple matter. 
There are many erroneous ideas on the subject, and much ignorance. In order 
to store compressed air, we must first have a receiver or tank sufficiently strong 
to withstand the pressure ; then it is simply a question of an air compressor and 
plenty of free air. The popular idea is that there is an enormous amount of heat 
developed which in some mysterious way has a bad effect during compression 
and storage ; that this heat all disappears, and that it is impossible to use this air 
without freezing, resulting in stoppage of ports and passages and serious hin- 
drance to the machinery. The heat of compression is no longer a bugbear in air 
compression. It is now under control to such an extent that by (fompound com- 
pression, or by compressing in stages with inter-coolers between each stage, the 
heat produced by the compression of air is not only reduced in degree, but the 
objections to it on the ground of economy no longer obtain. By the modern 
compound, condensing Corliss Air Compressor provided with quadruple com- 
pression cylinders and inter-coolers, compressed air may be delivered into the 
receiver at 2,000 pounds pressure, and at a temperature nearly equal to that at 
which it was taken into the compressor; that is, the temperature of the engnie 
room or of the atmosphere surrounding it. The heat loss— that is, the loss of 
power due to the heat of compression, which a few years ago ran as high as 50 
per cent.,— may now be brought down to 17 per cent. This large saving is due 
mainly to compound compression and inter-cooling, and it represents a marked 
advance in compressed air science. This fact alone should at least give com- 
pressed air engineers a hearing when pressing their claims for a better storage 



424 USE. 

system of street car propulsion than has been or can be produced by electricity. 
After compression the air is stored in tubes, which are made of solid ingots of 
mild steel, free from joints and welds, capable of standing pressures from 2,000 
to 4,000 pounds per square inch, and which do not explode. Even if an explo- 
sion should occur, or a weakness develop in the reservoir, there is not likely to 
be any serious result, because the rent which would quickly be made in the pipe 
would soon discharge its stored air. Were the material brittle the pieces might 
fly in all directions and do considerable damage, but the metal used for this pur- 
pose is soft and pliable, and would tear or stretch instead of break. A discharge 
or explosion from compressed air will not scald like steam, though it is likely to 
produce quite as much noise. 

Having compressed air stored in suitable receivers, it is simply a question 
of keeping them tight, and of providing a sufficient volume to run a car, locomo- 
tive or any other traction engine. Almost any design of engine which runs by 
steam will run equally as well by compressed air, but an air motor designed for 
use with air is better and more economical. Pneumatic engineers have already 
developed reheaters by means of which the stored compressed air before use in 
the engine is very much increased in temperature; hence its volume is increased 
and less air is required to do a certain work than when used cold. Reheaters 
will, of course, overcome all liability to freezing, but the main purpose of a re- 
heater is to save power. That it does this at an expense in fuel which is but in- 
significant in proportion to the gain, is a matter which cannot be disputed in view 
of recent facts of experience. Mr. Robert Hardie has practically demonstrated 
the fact that the cost of reheating air is about one-eighth the cost of compression. 
That is, it will only cost one-eighth as much to add a horse power to a com- 
pressed air volume as it originally costs to produce one horse power by the 
process of compression. 



AIR CARS. 

The air cars illustrated on the cover of this issue are those which have been 
operating for some time past on North Clark Street, Chicago, 111. The motors are 
the Hardie type and their service has been very satisfactory. In ordinary weather 
these cars simply do all that could be expected of them, but in time of storm, when 
snow and ice cover the tracks, they have proved to be able to cope with the 
emergency and the system appears to be adapted to all kinds of weather. The 
Compressed Air Company, 621 Broadway, New York, has issued a pamphlet 
showing the actual service given by the* air cars, and the numbers of passengers 
carried during very stormy weather. 

Mr. H. D, Cooke, president of the Compressed Air Company, has submitted 
the following statement showing the cost of operating compressed air motors for 
street car service. For the week ending December 2d, 1899, only 409 cubic feet of 
free air per mile was used by the air motor cars while carrying passengers, and 
not including an allowance for occasional trail cars. 

"Taking above as a basis of air consumption, and the statement of the cost 
of compressing air in large volumes as stated by the Ingersoll-Sergeant Com- 
pressor Company as being $0.0285 per 1,000 cubic feet compressed to 2,000 lbs. 



USE. • 425 

pressure, the cost per car mile (for large installations) 409-1,000 of $0.0285 = 
$0.0117 01" i^ round figures, i 2-10 cents per car mile. 

These figures cover cost of superintendence, labor, coal, waste, oil, interest 
on cost of power plant and a charge for annual depreciation. Price of coal is 
charged at $2.90 per ton. 

On this basis, and adding charges of wages, conductors and motormen, and 
labor of charging and repairing motors, the cost of operating per car mile in units 
of not less than 100 cars would be $0.0756 per car mile. 

This does not include general expenses, such as interest on, or repairs and 
maintenance of track and roadbed, or salaries of general officers, damage suits, etc. 

The noiseless air brakes, and the starting and stopping of the car with the 
small lever in the same movement (Hardie system) must reduce chances of acci- 
dents and consequent charges to damage account. These figures are based on the 
results of the present service in Chicago, covering a period of seven months, and 
also one year's experience on 125th street, New York. They were gone over, item 
by item, by practical street railroad men, and are based on actual facts, as stated." 



AIR CARS. 

The beginning of the new century seems to be a peculiarly fitting time for us 
to tell of the status of the compressed air motor in street car service, and it hap- 
pens that just at the present time we have also at hand data of sufficient interest 
and authority to warrant us in setting it forth. The readers of Compressed Air 
have been informed from time to time of the various installations of compressed 
air for operating street cars. Much of the record has not been of a character to 
encourage either the participants or the onlookers, and some who were interested 
and hopeful have dropped out of sight in connection with it. Compressed air 
seems, when first thought of, so simple in its operation, so easily understood, con- 
trolled and manipulated, that it has not received the proper study of its conditions, 
and in consequence many crude experiments have ended unsatisfactorily. Those 
who have stuck to it are to be praised for their perseverance, and to be con- 
gratulated for the present promise of gratifying and enduring success. 

The most interesting installation probably ever yet made of motor cars 
operated by compressed air is that of the 28th and 29th street crosstown line of 
the Metropolitan Street Railway Company of New York. It is interesting, espe- 
cially in the fact that it is a complete installation, no other cars being operated 
upon the line either night or day but the compressed air cars. In this plant, as 
elsewhere in compressed air trials, it would seem that the best conditions were 
not at the first insisted upon. Indeed some mistakes were evidently made. The 
tracks of this line were cheaply and hastily laid some ten years ago for the light 
horse cars of that time, with no thought of any heavier traffic, and 
the track had not been maintained in proper condition, and upon this track 
the air cars were started. The tracks have since been relaid, and are 
now in fair condition for the service. We cannot but think also that 
it was a rash and risky thing to do to start a permanent service of this respon- 




426 



USE. 



I 



sible character with a single unit of supply at the power house. However perfect 
and adequate the apparatus, there are too many possibilities of accident or de- 
rangement for the risk to be taken. The compressor in use is also of much 
larger capacity than the present service requires, it having been designed in con- 
templation of partially supplying a much more extensive service, which it was 
hoped would be and is now confidently expected, will be developed. The com- 
pressor is easily capable of supplying three times the number of cars now in ser- 
vice, or three times each day the business of that which it at present supplies. 
The compressor is now run at 27 revolutions per minute, when it might be run 
at 75 revolutions. No larger force of men, of course, would be required for the 
increased speed, although a few more men would be required in the car shed. 

The following is an official statement of the running of the present cars since 
they have been in steady operation. It will be noticed in connection with this 
statement that the number of cars in operation at the beginning of the perioH was 
considerably less than at the last of it. On the day of the Sound Money Parade 
the running of the cars was stopped entirely by the obstruction of the streets for 
eight or ten hours. 

RECORD OF AIR CARS BEING OPERATED ON 28tH AND 29TH STREETS, NEW YORK CITY. — 

ROUND TRIP 5.5 MILES. 



Date. 1901. 


No. of Cars 
in Opr. 


Round 
Trips. 


Total Mlge. 


Total Pass. 
Carried. 


September ...26 


13 


186 


1023 


13,271 


27 


13 


215 


1 182 


13,724 


28 


13 


218 


1 190 


13,710 


29 


13 


222 


I22I 


15,544 


30 


13 


234 


1287 


11,840 Sunday 


October i 


13 


222 


I22I 


14,474 


2 


15 


219 


1204.5 


14,476 


3 


15 


252 


1386 


16,253 


4 


16 


256 


1408 


16,231 


5 


16 


270 


1485 


16,968 


6 


16 


269 


1479-5 


17,670 


7 


15 


239 


1314.5 


13,240 Sunday. 


8 


16 


269 


1479.5 


19,069 


9 


17 


302 


1661 


18,690 


10 


17 


302 


1661 


18,078 


II 


17 


340 


1870 


18,599 


12 


17 


320 


1760 


18,455 


13 


17 


332 


1826 


22,081 


14 


18 


245 


1347.5 


12,197 Sunday. 


15 


18 


330 


1815 


19,520 


16 


18 


346 


1903 


21,142 


17 


18 


340 


1870 


18,862 


18 


18 


328 


1804 


18,692 


19 


18 


341 


1875.5 


18,618 


20 


18 


334 


1837 


19,672 









USE. 



427 



D«t«> iqno No. Of Cars Round Total Ml ^e Total Pass. 

Date. 190U. inOpr. Trips. Joiaimi^e. camed. 

21 18 245 1347-5 14409 Sunday. 

22 19 330 1815 19,890 

23 19 324 1782 20,052 

24 19 343 1886.5 20,972 

25 19 354 1947 19,074 

26 19 349 1919-5 19,857 

27 19 356 1958 22,173 

28 18 245 1347-5 12,324 Sunday. 

29 19 331 1820.5 19,421 

30 19 335 1842.5 19,341 

31 19 327 1798.5 19,062 
November .... i 20 340 1870 19,274 

2 19 345 1897-5 19,978 

3 19 197 1083.5 12,730 Sound Money Parade. 

4 16 245 1347-5 13,470 Sunday. 

5 20 351 1930.5 19,846 

6 17 256 1408 15,440 Election Day. 

7 18 352 1936 2i',3i7 

8 19 334 1837 20,274 

9 19 339 1864.5 19,194 

10 19 341 1875.5 20,035 

11 16 244 1342 12,860 Sunday. 

12 20 338 1859 19,525 

13 20 353 1941-5 19,738 

14 20 354 1947 20,056 

15 20 352 1936 19,506 

16 20 352 1936 19,228 

17 20 353 1941-5 22,231 

18 15 245 1347-5 13,454 Sunday. 

19 20 348 1914 20,557 

20 20 338 1859 20,390 

21 20 350 1925 20,785 

Total round trips I7.i97 

Total mileage 94.583-5 

Total passengers carried 1,017.269 

Average number passengers per trip 59.15 

Average number cars running 17.5 

Average number daily trips per car 17.2 

Average number miles per day per car 94.6 

The following is the computed total cost of operating 20 compressed air cars 
on the 28th and 29th streets (New York) line under present conditions: 

Cents per 
REPAIRS. car mile. 

Including material, supervision, and 9 men, adjusting valves, piping, 
brakes, rods, brasses, labor, etc., $35.00 per day 2. 



428 USE. 

CHARGING STATION. 
Including oil, waste, foreman, charging gang (2 shifts), oilers, clean- 
ers, etc., $28.00 per day 1.60 

POWER HOUSE. 
Including engineers, coal passers, pipe fitter, machinist, oilers, etc., 

and 16 tons coal per day, oil, waste, etc., $82.50 per day 4.71 



Cents per car mile 8.31 

Conductors and motormen, inspectors, roadbed, ties and timber, remov- 
ing snow, salaries of officers, switches, material, etc 9.1 1 



Cents per car mile 17.42 

The above computation is made on a basis of 1,750 miles per day, and al- 
though every charge is made for the present operating of only 20 cars, yet from 
60 to 80 cars could be operated by the charging and power plant without any ma- 
terial increase in cost, so that for a more extensive installation the cost of operat- j 
ing would be materially reduced. 

As a reminder to our readers it will be well for us here to recapitulate the 
principal features of the above installation. The air compressing plant and the 1 
shops are at 12th avenue and 24th street. The compressor comprises a 1,000 h.-p. 
Reynolds-Corliss, vertical, cross-compound, condensing engine with cylinders 
32" and 68" in. diameter and 60" stroke, running with present load at 27 revolu- 
tions per minute under a boiler pressure of 150 pounds, the piston rods of the 
steam cylinders being extended below into the air cylinders of a four-stage Inger- 
soll-Sergeant air compressor. The successive diameters of the air cylinders are 
46", 19", 13.75" and 6"' with the common stroke of 60". Effective intercoolers 
are of course provided between the successive stages and after the final compres- 
sion. The compressor is designed to compress 3,750 cubic feet of free air per 
minute to a pressure of 2,500 pounds to the sq. in. Four Babcock & Wilcox boil- 
ers of 250 h.-p. each supply all the steam for the compressor and also for the 
shops and for the hot water service of the motors, which latter is a future essen- 
tial to their economical operation. 

The storage capacity at the station for the compressed air is now 1,050 cubic 
feet, which can easily be enlarged at will by successive addition of "bottles." 
Two cars may be charged at once with air and with the hot water for reheating, 
the entire operation for each car requiring about two minutes. The cars can 
make two round trips for each charge. They have Pintsch gas lights, the most 
effective air brakes ever employed and means for heating the cars during the 
cold season. The cars have each a storage capacity of 55 cubic feet of air at the 
maximum pressure. Nothing about the car in any way interferes with the pas- 
sengers any more than in any other car. The operating devices on each platform 
consist of a reversing lever, throttle lever, air brake lever and a valve for shut- 
ting off the air storage. There is a pressure gauge visible, and a hand brake is 
retained for emergencies. 

The cars are 32 feet long over all, the body being 22 feet, and seating 30 per- 
sons. The weight of the motor truck is 11,000 pounds and the total weight of the 



USE. 429 

car in running order is 19,000 pounds. The car body is carried on elliptic springs 
that rest directly on the truck frame and are pivoted by special fulcrum to the 
car body. The driving wheel axles are journaled in regular locomotive style, and 
have the usual driving box spring suspension. The cars run steadily and smooth- 
ly and there is no jerking in stopping or starting. 

The first passage of the air from the storage system of the car is controlled 
by a valve on the platform. It first passes the reducing valve, beyond which 
the uniform pressure of 150 pounds is maintained. Before entering the cylinders 
for work it goes through the hot water tank or reheater. It enters at the bot- 
tom by small perforations in a long pipe lying along the top, and thence to the 
throttle valve. The use of the reheater has been experimentally proved to almost 
exactly double the efficiency of the air used. The Hardie improved cut-off valve 
gear secures high economy in the expansive use of the air in the motor cylinders 
under the wide and sudden variations of load. 

The report of the Metropolitan Street Railway Company for the year ending 
June 30, 1900, gives the relative and actual costs of operating cable, electric and 
horse railroads. For horse cars the average was 18.98 cents per car mile, the 
cars being much smaller than those of the other systems; for cable cars, 17.76 
cents, and for electric cars, 13.16 cents. The figures were made to include all ex- 
penses of operation and maintenance. The estimate given may be assumed to 
show very nearly the best attainable results by either of the systems at present. 

1 The figures given in the computations relating to the air cars evidently do not give 
the best results, as the conditions are far from being the best that can be secured 
with pur present knowledge. The compressor, as was stated, is very much too 
large for the present service and works at a constant loss. The plant has all the 
disadvantages of a new plant in the inexperience and lack of trained judgment of 
the men employed. It is to be noted that the expenses for repairs, two cents per 

. car mile, are even now remarkably low for any system except the horse-car. On 
a recent visit to the shops we asked the superintendent what the repairs chiefly 

, consisted in, and he said that there were really no repairs required, what went 
under that term was the occasional taking up of the brasses and the usual read- 
justments of the working parts, as with a first-class locomotive. Of the 20 cars, 

. which is the total number on the line, there is seldom more than one at a time un- 

• dergoing these "repairs." The estimate of the Compressed Air Company that the 
running expenses can be reduced to 13.57 cents per car mile, when the conditions 

J are all correctly adapted to the work, does not seem to be unreasonable. With 

. this figure crowding so closely the operating expenses of the electric cars it is to 
be remembered that the air cars have not in addition the enormous fixed charges 
for the construction of the roadbed which the electric cars labor under, so that 
with this load added to the electric service the balance is greatly in favor of the 

I air cars. 

The most important practical evidence of the favorable light in which the 

j, compressed air cars are at present regarded is in the fact that the installation of 
which we have been speaking was formally taken possession of by the Metro- 
politan Street Railway Company on Dec. 13th last. This does not necessarily 

, mean that this system is at once to be adopted in place of the large number of 
horse cars still running upon the various crosstown and other lines of the city, 




^ill 



430 USE. 

but that It has at least so far demonstrated its desirability as to make it worth 
while for the greatest street railway system of the world to undertake for itself 
to get at the bottom facts in the case. The full service is to be maintained upon 
the line where it is now in operation, and trials of the Hardie cars are soon to 
be made upon other lines. Not only the general principles of the system and its 
general efficiency is to be completely determined, but it is also necessary to know 
the size of car and the motor and storage capacity best adapted to all conditions. 
Another car is nearly completed which embodies in every detail of it every im- 
provement which experience has suggested. This car is to have a considerably in- 
creased storage capacity, so that it will be capable of running 25 miles upon a 
single charge of air, and this car will be tried upon any line that may be suggested. 
The absolute independence of these cars when charged leads to many suggestions 
of combination routes for them to run on, as with an omnibus system, for the 
accommodation of the public by quick transit and the avoidance of transfers. 
Other things being equal, the independence of all connection with the power house 
and the easy manipulation of the car as long as its charge holds out give the air 
cars a great advantage, to which is to be added their speed and safety and smooth- 
ness of running. 

At present it must be said that the compressed air car in New York is com- 
manding respectful consideration. Too much can scarcely be said of the en- 
gineering ability and farsightedness of Mr. Robert Hardie, who so long ago so 
completely designed the present system of operation and of the perseverance both 
of himself and of Mr. H. D. Cooke, who is still pushing as resolutely and as 
earnestly as ever. 



AIR CARS. 

The illustration shown. Fig. 140, is a view of the new Hardie Com- 
pressed-Air Motor Car. In view of recent events on the 28th and 29. h 
streets lines in New York City, this car is interesting in that it has recently 
been decided to substitute an improved form of the Hardie car for the experi- 
mental cars that have been removed from the 28th and 29th street lines. These 
Hardie cars are admitted to be the best in the line of pneumatic storage cars. 
They are built on the basis of a large experience in which Mr, Robert Hardie 
has been personally the active mechanical engineer, watching results and chang- 
ing and simplifying the motor on lines of experience. This in itself should 
inspire confidence, but in addition we have the facts before us that the Hardie | 
motor was in operation in New York for one year on 125th street, during which 
time a complete record was kept and this rcord is open for inspection. The work 
done was satisfactory to the officers of the Railroad Company, and to the thou- 
sands of patrons of the road who used them daily. It is a matter of note that, 
unlike the cars recently removed from the 28th and 29th streets lines, these cars 
on 125th street were so easy of movement that the general public were uncon- 
scious of the fact that they were being drawn by air as distinguished from any 
other form of motor. These motors were afterwards taken to Chicago, where 
they have been in daily operation for about fifteen months, and recently they have 



USE. 



431 



been purchased by the Chicago Company, the purchase comprising the entire 
plant, two cars and the air compressor. They are used in Chicago as "Owl 
cars," running at night on cable roads. During the severe snow storms of the 
past winter they ran satisfactorily. The work in operation now on the 28th and 
29th streets line is to prepare the road bed for these cars. The old light rails 
that were used are being replaced by others sufficiently heavy to carry the air 




FIG. 140 — THE NEW HARDIE AIR MOTOR ON THE METROPOLITAN STREET RAILWAY 

CARS, NEW YORK. 



cars. It is but natural that an air car, or, in fact, any form of motor car, should 
be heavier than a horse car, but the Hardie air cars are lighter than the electric 
storage cars and compare favorably in weight with any other system of power 
traction. The Metropolitan Street Railway Company, of New York, has ordered 
twenty-eight of these cars for service on the streets and have placed with the 
Compressed Air Company, an additional order for one hundred air cars to be 
taken after the twenty-eight have been put into operation as per agreement. 



432 USE. 

These facts are important to railroad men and engineers in that they indi- 
cate the practicability of using independent motors which are always appreciated 
because they are complete in themselves, carrying their own power, and can be 
readily removed from the track and taken to the shop, in this way avoiding inter- 
ruption to the general traffic of the road. 



AIR POWER CARS IN CHICAGO. 

The first trip in Chicago of a car operated by compressed air was made the 
evening of May 12 over the tracks of the North Chicago street railroad company 
between the limits barns and Washington street. The run was made in place of 
the first "owl" car. The experiment was so successful the company will supply 
at once all its north side lines with similar cars in place of the horse cars which 
now make the night trips. 

People who caught the compressed air car were surprised to find them- 
selves at the limits barns in twenty-five minutes, including a stop of five minutes 
at the Elm street power house. The car proved capable of any speed desired, 
ran without noise, and was under perfect control. 

Robert Hardie, inventor of the car, was the engineer, and Otto Berthold 
collected the few fares. The passengers were mostly officials and others inter- 
ested in the test. Henry D. Cook and A. C. Soper, officers of the Compressed 
Air Motor Company, were among them. The actual running time from the Elm 
street power house to Washington street and return to the limits barns was 
twenty-eight minutes. 



THE NEW TRAMWAY. 



Horse cars are the ruin of street railways, therefore all cities are at present 
trying to substitute some means of mechanical traction, such as electricity or com- 
pressed air. 

The electric traction known as "The Trolley," with its overhead system of 
wires and return by rail, has been somewhat developed in France through lack of 
anything better, but it carries with it many disadvantages. From a purely 
sesthetical point of view it disfigures our cities with its many posts and the 
network of wires of which it is composed. Looked at from a point of safety, its 
many victims in Bordeaux, Lyons, Marseilles, Brussels, Genes, etc., testify against 
it, to say nothing of the great havoc it has played with telegraph and telephone 
lines, water ??nd gas pipes, etc. In the United States, from whence we received 
this system, New York, Washington and other large cities have prohibited its 
adoption. 

In Paris, the "Compagnie des Omnibus," noting all these disadvantages, has 
used compressed air as one of its means of traction, though the methods employed 
up to date have been much more costly than had electricity been adopted. It has 
been necessary to use very high pressures in order to supply a sufficient amount 
of compressed air to last for the entire trip of the tramway. That necessitated 



USE. 433 

having numerous engines, caused a considerable loss of time, and forced the build- 
ing of heavy cars with large receivers, which materially added to the dead 
weight of the tramway. It became imperative to find a better and more economical 
method of utilizing compressed air, and that is what MM. Popp and Conti have 
done. They have presented to the members of the General Council of the Seine, 
to the Municipal Council of Paris, as well as to the chief engineers employed by 
the government, a tramway which seems to give absolute satisfaction. Though of 
light weight and graceful form, it is sufficiently strong to draw several other cars 
and also to accommodate forty passengers, who suffer no inconvenience from heat, 
unpleasant odors or disagreeable noises. It moves easily and rapidly, stopping 
quietly or suddenly at the will of the motorman, if by chance a horse or carriage 
crosses its path. It is even able to back on the track without disturbing either the 
passengers who are in the tramway or those who are on the two large platforms 
outside. At starting, the tramway is charged with a sufficient quantity of com- 
pressed air to enable it to run for four kilometres, after which distance it becomes 
self-charging, and by the following ingenious device. 

Before each waiting station the rails are provided with a pipe which is set 
in the hollow over which the wheels pass. That causes a smaller pipe to spring 
from the ground and enter a hydraulic joint placed under the tramway, by which 
means the receivers installed there are connected with the undrground conduit. 
The amount of compressed air received in a few seconds is sufficient to propel the 
tramway for a further distance of four kilometres. This done, the little pipe re- 
enters the ground and is automatically covered by an iron plate, over which men 
and horses alike may pass with perfect safety. 

The Presidents of the General and Municipal Councils, as well as the mem- 
bers and the eminent engineers, MM. Huet, Boreux, Humblot, Petsch, Mon- 
merque, &c., who were present at the tests, warmly congratulated M. Victor Popp 
upon his success. 

In conclusion, we trust Paris will follow in the footsteps of Saint-Quentin, 
Angouleme and Lyons, who have already adopted this system, and not wait for 
the Exposition of 1900 before giving the public a means of transportation which 
will be so greatly to its advantage. Charles chincholle. 

Translated from The Figaro, 



AIR POWER REFLECTIONS. 



Compressed air is speaking daily for itself, through the various machines 
in which it is used. The physical part of man is itself only a machine which 
uses air. Sir John Lubbock says, "Men, like trees, live in great part on air;" 
and Oliver Wendell Holmes says, "Laughter and tears are meant to turn the 
wheels of the same sensibility, one is wind-power and the other is water- 
power." 

Man's motive power is air. He breathes 40 times a minute. Hardie's 
motor takes a breath every 13 or 17 miles of travel, using air at a constant of a 
little over 100 lbs. p.essure and stores it for convenience at 2,000 lbs. pressure. 



434 



USE. 



Air has never, to my knowledge, been tried and found wanting. It has 
been used from the earliest days more prominently to propel ships and work 
wind-mills, and for other purposes, but its first general application, which brought 
it prominently to the public notice as a mechanical force, was its adoption in the 
Westinghouse and other air brakes. It was strange that this did not suggest 
the thought that what was good to stop the train was equally good to start it. 
And it is a curious fact that even at this late date the electric trains upon the ele- 
vated roads in Chicago, which are propelled by electricity, use the current from 
the rail at the moments of rest to work an air pump to store air to stop the 
train. The only reason air is used to stop these trains is because mechanical ex- 
perience has proven that there is nothing better than air for that purpose, and 
in my opinion, the only reason why air is not used to start the trains is because 
it has never yet been tried. Wherever air has been used it gives satisfaction. 
There is no more economical power distribution than by compressed air, for 
the reason that this power once made it can be saved in storage pipes and re- 
heated at time of using, which gives an advantage over electricity. In storing 




FIG. 141 — JUDSON AIR CAR AND TRAILER. 



air in pipes and reservoirs, there is little waste and scarcely any depreciation in 
material. The fact that air is good for small machines is equally true of large 
machines, and its uses are being extended from day to day, until there are many 
who believe that in the near future air will be commonly supplied throughout 
cities in the same manner as water and gas. 

The fact that electricity has been taken up so prematurely by street rail- 
ways has given it imdue prominence as a power distributor, and has crowded 
out of notice its less pretentious ally — compressed air — which has been gradually 
introduced into service upon the steam railroads, in shops, mines and general 
mechanical work, until it is a question w^hether there is not fully as much power 
conveyed to-day by compressed air as by electricity, though the air is used in 
out-of-the-way places where its growth has not been remarked. 

My attention was first directed to compressed air in 1888 at the Minne- 
apolis Exposition, where I saw a small car 22 in. long and 8 in. wide, which 
was operated by levers placed in a trench between a small circular track laid out 
on a table. Movement was imparted to the car by a lever which seized a trian- 
gular cam, and in making half a revolution passed the car on 16 feet. This 



USE. 



435 



cam was attached to an apparatus, which was connected to the car through the 
slot, and when one lever let go another lever took hold, and so on. What sur- 
prised me was that the air power which operated the cylinders that moved the 
cam levers was conveyed in a lead pipe not larger than a lead pencil, and the hole 
conveying the air was no larger in diameter than the lead of an ordinary pencil. 

On this car I saw a man who weighed 229 lbs., and who was carried 
around this track at speed. To hold on to the car it was necessary for him to 
kneel down with his feet hanging over one end of the car. This exhibition sug- 
gested thoughts of the power of air, which I had only considered in a general 
way up to that date. 

In 1891, principally through the efforts of a party of friends in Chicago, a 
geared motor car was built at Pullman and a charging device constructed by 




FIG. 142 — IIARDIE CAR NO. I. 



which the car was automatically charged while passing over a specially con- 
structed pit. Air in this motor was only used at 190 lbs. pressure, and the 
motor travelled 4J/2 miles with one charge of air. These patents are now all 
owned by the American Air Power Co., but Robert Hardie's experience has 
proved that air at high pressure is easily and safely handled, and possesses many 
commercial advantages which recommend it above the use of low pressure. 

During the construction of the World's Fair Buildings at Chicago, a 
proposition was made by the parties interested with me at that time to construct 
the intermural railroad in the fair grounds, and operate it with compressed air. 
The proposition was to charge only 5 cts. fare, and divide the profits after the 
structure was paid for. The electric people, however, controlled the situation 
and made a contract to charge 10 cts. fare and give the World's Fair people half 
from the start, which was more to their liking, and therefore compressed air 



436 



USE. 



was turned down, or it. would have made its advent as a motive power m this 
country at an earlier date than it has. Subsequently I had the good fortune to 
form the acquaintance of Mr. Robert Hardie, whose knowledge and practical 
experience in the use of compressed air at high pressures, and whose ability as 
a mechanical engineer impress all who come in contact with him, and are borne 
out by the great merit of his devices, I was much impressed by Mr. Hardie's 
plans, and was one of the humble instruments in bringing together the combina- 
tion which joined in putting Mr. Hardie's inventions before the notice of the 
public. 

The merits of Hardie's inventions class him in the foremost rank of the 
inventors of this century. All of his promises have been more than fulfilled, 
and his knowledge and experience were the one thing necessary to perfect the 




FIG. 143 — HARDIE MOTOR, 1879. 



motor up to the severe requirements of the street railroads of the present day. 1 
Motors constructed under his supervision have been practically tested by the I 
combination represented by the American Air Power Co. for the last three years, ' 
and latterly two of them have performed daily schedule on 125th Street since 
August 3d, last. In every respect they have fulfilled the most sanguine expecta- 
tions, indeed surpassed them, and two of them have travelled about 24,000 miles 
and carried about 140,000 passengers without serious delay or accident. 

Compressed air in this field proves itself equal to any and all emergencies. 
It is nature's prominent force, which she uses to stir the heavy waters of the - 
ocean and prevent their stagnation, or to perform lighter service, such as to carry I 
seeds. It is the natural ally of steam to distribute its force. It is not as wasteful 
as electricity nor as destructive. It is one of nature's vehicles of motion. What 
can man do better than to imitate nature? henry d. cooke. 



m^ 



USE. 437 

PNEUMATIC TRACTION. 

We present the case of Pneumatic Traction as it stands up to date. 
Special attention is called to the facts and figures given by Mr. Pettee in tha 
paper entitled, "Cost of Operating Air Cars in New York City." That the Har- 
die air motor represents an advance in street car propulsion by compressed air, 
will, we think, be generally admitted. One of these cars has been in continuous 
operation in New York since last August, carrying passengers, and to all out- 
ward appearances, differing but little from the regular cable and electric cars. 
This is the first time that a compressed air car has done regular and successful 
commercial service in America for any length of time. All previous attempts 
may be classed as experimental and it is a fact worthy of notice that these ex- 
periments have usually failed to produce permanent results, not because of me- 
chanical failures, but owing to lack of funds. To develop a new system of 
power for tramways is an undertaking which involves a large expenditure of 
money. Those who are familiar with the early experiments with the trolley 
know how expensive it was to get started, and what an enormous amount of 
money was consumed in experiments before commercial success was reached. 
The late Mr. Franklin Leonard Pope said that compressed air traction would 
now be successful, had there been spent upon it even a fractional part of the 
money and brains that have been used in the development of electricity as a 
motive power for street railroads. Electricity has always been popular as an 
investment. Its marvelous success in the telegraph, telephone and elsewhere 
led capitalists to contribute largely toward its use for street cars, and its final 
success was the result of the strong combination of capital and brains, which 
combined steadily and faithfully through so many years. 

It is only during recent years that the storage system of compressed air 
traction has been made practicable. A successful storage system involves an air 
compressor capable of economically producing air power at a pressure of about 
2,000 lbs. per square inch. In order to do this economically, compound com- 
pression becomes necessary. The modern high duty compound compressor con- 
sists of four cylinders compressing in four stages, with intercoolers between each 
stage. A Corliss engine furnishes the power and the air is delivered at 2,500 
lbs. per square inch, and at a temperature about equal to that in the initial stage. 
The heat loss, that is the loss of power due to the heat of compression, which 
at these high pressures with single stage compressors was as high as 50%, is 
now brought down to 17%. In addition to this, the Corliss mechanism produces 
a H. p. with an evaporation of less than 16 lbs. of water, consuming less than 
2 lbs. of coal. After compression the air is stored in tubes which are made of 
solid ingots of mild steel free from welds and capable of standing pressures as 
high as 4,000 lbs. per square inch. It is only during recent years that these 
storage reservoirs have been brought to the point of absolute safety. Thus we 
see that air power may be produced and stored safely and economically, and as 
compressed air is capable of driving an engine designed for steam power, the 
problem resolves itself to a common reciprocating engine as a motor to drive 
the car. For the sake of economy the air motor is of special construction, usii^g 
hot air and cutting off early in the stroke, expanding and exhausting at atmos- 
pheric pressure. 



43« USE. 

PNEUMATIC TRACTION IN NEW YORK. 

The installation of a large compressed air plant on West 23d Street, New 
York, for the purpose of supplying power to street cars on the 28th and 29th Street 
lines, is an important event in compressed air history. It is also a hopeful indica- 
tion that pneumatic traction may become of useful commercial interest. 

Certain facts may be asserted with confidence. The American Air Power 
Company has arranged with the Metropolitan Traction Company to install an air 
compressor of 1,000 h. p. capacity for street car purposes. The Air Power Com- 
pany has also contracted with certain well known manufacturers of machinery 
to build this plant. Looking into the details of the case we find that this installa- 
tion is to be unlike any that has heretofore been brought to public notice in 
America. In the first place the business is in the hands of the Traction people, 
who have the experience and the money to develop this new system for street 
car propulsion. In the second place, this case appears to have been wisely con- 
sidered by business men, and an order given for a plant of machinery which rep- 
resents the best that modern mechanical science can devise. The makers are not 
restricted to anything on lines of economy or on the plea of temporary use, but 
are asked to build the best machinery that can be devised for this purpose, and in 
a unit so large that it is reasonable to expect a condition of economy in the pro- 
duction of compressed air which has not heretofore been reached. 

This appears, in a measure, to be a development of pneumatic traction ex- 
periments which have been carried on at infrequent intervals and in a rather er- 
ratic manner since 1879. Efforts twice made by the Hardie motor to find a place on 
the Elevated Railroad should not be belittled in the light of present knowledge, 
because, while ill-advised from a business standpoint, they were important 
mechanically in that it was demonstrated that a train of cars could be handled 
with reasonable economy by an air motor. 

Pneumatic experiments on the elevated road cannot be called mechanical 
failures ; hence the results do not reflect discredit either upon compressed air or 
upon the engineers engaged in them. Their chief weakness was in attempting to 
develop an important pneumatic application by beginning at the top. The Judson 
system which was installed at Washington, D. C, attracted attention to pneumatic 
traction, and suggested, perhaps, some of its possibilities. The experiments with 
the Mekarski system had a like influence, but this system did more than the other 
in that it confirmed the confidence of engineers in the storage system for pneu- 
matic traction. The work of Jarvis, Parke, Hoadley and Knight was in the nature 
of an advance, developing new ideas and profiting by earlier experiences of others. 
One of the difficulties against which pneumatic traction has had to contend, is that 
there was too much speculation in it. Time and money were spent in selling 
rights, in developing patents and in the organization of companies, which might 
have been spent to better advantage in the equipment of a small street railroad. 
The common error has been made in supposing that compressed air was the com- 
ing power for street railroads, and that it would replace all others. Compressed 
air is only one among other useful means by which street cars may be driven. It 
has its place alongside of electricity, and perhaps closely associated with it, but it 
is not at all likely to drive electricity out of the field. 



USE. 439 

The American Air Power Company is a consolidation of all American 
pneumatic traction interests. This company controls most of the patents on this 
subject. On its staff are the engineers who have had the experience, and on its 
Board of Directors are men who know the street car business. Mr. H. H. Vree 
land, President of the Metropolitan Traction Company, has a hand in this matter 
in no uncertain way. Mr. Vreeland has never been known to be windy on this 
or any other subject. He thinks, perhaps, that there may be a field for com- 
pressed air on cross-town service, where the runs are shorter, and where the 
independent motor will be useful in traveling on different tracks, and where its 
use will not involve a large expense in construction, which is necessary when the 
overhead trolley cannot be used. 

It is perhaps true that the officers of the Traction Company are not yet 
confident believers in the success of pneumatic traction, but those who have 
greater confidence than this should be well pleased at the opportunity which will 
here be afforded to prove this case under the eyes and supervision of President 
Vreeland, supported by men who have at least thus far shown a willingness to 
pay for a demonstration which is not restricted for want of funds and which has 
at least been started in a way that indicates permanence. 



PNEUMATIC TRACTION. 



We have never been enthusiastic over pneumatic traction. Our readers 
will recall several publications in this paper containing descriptions of street car 
motor propelled by compressed air. We have also touched upon the subject 
editorially, and have always made an effort to watch the developments closely 
following all designs, both theoretically and practically, believing as we always 
have that ultimately a street car propelled by compressed air would be developed 
and put into constant practical service. 

The June number of this paper contained an original description with illus- 
trations of the pneumatic system which has recently been put into operation in 
New York City. This cannot be called a new system. It is simply a develop- 
ment based on large experience. Heretofore running street cars by compressed 
air has been experimental only; that is, one or more cars have been built and 
run experimental from time to time with a view of attracting attention, inter- 
esting capital, with the purpose in mind to equip a road. The most important 
step toward the solution of this problem was made by the American Air Power 
Co. when it ran a car steadily for one year on the 125th street line, New York. 
This was a Hardie car and the results obtained were quite satisfactory. The 
length of service enabled the engineers of the company to figure closely as to the 
rost of operation, volume of air consumed, repairs, percentage of grades, etc. 
in this experiment the total average daily mileage was 125.16 miles, and the total 
distance covered, 23,000 miles; the total number of passengers carried, 137,386. 
At that point the car traveled on a grade of 7 7-10 per cent, for a short distance. 
The expense of operating including coal and water items, and all labor, includ- 
ing night-watchman, record-keeper and switchman, for a portion of the time 



440 USE. 

figure about $.26 per car mile. When based on two-car service during the latter 
period of the experiment the cost was brought down to a little over $.20 per car 
mile. Mr. Pettee, the engineer in charge, states that if the proportion of labor 
actually utilized in this service is considered, the expense would only amount to 
about $.18 per car mile. These figures are all based on the services of one or 
two cars with an air compressing plant to average economy, and should not be 
reckoned in comparing with the cost of operating the entire system of street cars 
of any other power. In fact, it is safe to assume that based on this experience, a 
large equipment of cars might be run at an expense of about $.12 per car mile. 
The Hardie car in this work showed an average consumption of a little over 400 
cubic feet of free air per car mile, though at times the consumption was less 
than 400, and it is not difficult to understand wherein improvements might be 
made which will reduce this consumption considerably. In fact, it is claimed by 
persons connected with the Air Power Company that the cars of the 28th and 
29th street lines will consume only about 350 cubic feet of free air per car mile. 

The system of reheating employed on the Hardie and the Hoadley-Knight 
cars is from steam and hot water; this adds largely to the economy of air con- 
sumption, but it cannot compare in efficiency with the dry system of reheating 
which is likely to be the system adopted for the future. The cost of compressing 
air up to 2,500 lbs. pressure per square inch is about $.05 per thousand cubic feet 
of free air when based on plants of average capacity. It is likely that this cost 
can be reduced and it will be interesting to note the results of a test made on the 
large air compressor which was described in our June number, and which is now 
installed at West 24th street, New York, for the purpose of compressing large 
volumes of air up to 2,500 lbs. pressure. As the cost of motive power is merely 
but a fraction in the cost of operation in street car services, perhaps from $.02j^ 
to $.03 per car mile would represent the cost of motive power when based on the 
experience of 125th street, the balance is chargeable to repairs, administrations, 
etc. The item of repairs is an important one and will be watched with great 
interest in the 28th and 29th street lines. 

Several cars are in regular operation for carrying passengers crosstown in 
New York, and as they are similar in every respect to the original electric cars, 
they attract little or no attention. The cars are noiseless, free from all odor, and 
perfectly safe, each car being an automobile, running with its own power and 
entirely independent of a central connection. This feature is important in cars at 
service as it admits of running on different tracks, and practically makes an inde- 
pendent automobile 'bus out of the street car. 

The plant now running in New York is, we think, without question, the 
highest type of pneumatic equipment for this purpose which has been brought 
to our attention. Improvements have been made throughout the system in the 
air compressor, and in the motors which promises well. There is really nothing 
very experimental about this plant, as it follows closely well established railway 
practice. The cars are the standard of The Metropolitan Street Railway Com- 
pany. They are built on the standard Brill truck, air motors being simply sub- 
stituted for electric motors; the weight of the motor being partially on the car 
axle, all other parts are mounted on the car body. It looks very much to us as 
though this plant had been installed to stay. The entire system is so thoroughly 



f 



USE. 441 



modern and the installation so large and at so great an expense that it has the air 
of permanency, and, in fact, we look for its development from this starting point 
to other lines. 



Paris, May 14, 1899. 
Editor Compressed Air: 

I have been just now reading in your Vol. IV. No. 2 of April, isgg, an 
interview of Mr. Abdank, which was taken by an Evening Post reporter. 

Before discussing this subject, I must remark that Mr. Abdank, who is in 
the "Societe Francaise de Procidis Electriques Thomson-Houston" in Paris, has 
never had anything to do with the mechanical traction applied to tramcars and 
overall to pneumatic traction. Therefore, it must be admitted that his authority 
on the subject is discreditable and his assertion that in France the problem is 
definitely solved by the adoption of the trolley electric system and pneumatic 
tramway practically discarded, is the best proof that he is not very well ac- 
quainted with the subject he is treating, and the best proof is the Paris Com- 
pagnie des Omnibus, the most important of the French companies, who has given 
a fair trial to all kinds, has pneumatic cars on different lines, and is now building 
a new station of 5,000 horse power with air compressors, and has enlarged the 
number of its pneumatic cars from 100 to 250. 

As may be therefore easily understood, Mr. Abdank takes his dreams as 
facts. 

Reviewing the technical part of this interview, we must again remark that 
he is making another mistake when saying : "The compressed air system involves 
a larger number of transformations of energy than the electric system." Al- 
though Mr. Abdank is described as an eminent consulting engineer, we must 
confess that after having read this part of his interview, we would not care to 
consult him on the subject; the reason is: Compare both systems and you will 
find that they require for the initial transformation: 

Steam boiler and dynamo for electricity; steam boiler and compressor for 
compressed air. No difference, no more complication in one case than in the 
other. 

The net loss practical of energy in the compressor is of less than 10-15%, 
the loss of the dynamo is wholly equal. Again no difference. 

I may claim that, having built and established in Paris, ist, 8,000 H. P. 
of compressed air works; 2d, 10,000 H. P. of electric works, for distribution of 
light and energy throughout the city, I know and perhaps am the only one who 
knows that the loss in initial transformation is about equal in both systems. 
Proofs at disposal. 

The distribution is afterwards obtained ist, by condensation for compressed 
air; 2d, by cable for electricitj'. There the advantage remains entirely for dif- 
ferent reasons with the compressed air. 

Cost of canalisation is smaller (50%) loss of energy, lessened smaller re- 
sistance. 

The trolley system necessitates as many miles and yards of cables as there 
are of lines. 



442 USE. 

Compressed air does not necessitate any canalisation if the line is of less 
than four or five miles, or if longer, it does not necessitate more than one-half 
the line or even less. 

The compressed air motor car line has another advantage, viz. : Each car 
carries its own power with itself, and therefore the service is not liable to be 
totally interrupted all at once, as has often been the case when one serious acci- 
dent happened on the line or to the cable of the trolley. The proof is: The 
works I have erected in Paris in 1880 have at present a canalisation of 180 miles, 
distributing energy to 2,000 H. P. lifts, etc., in 2,000 houses and winding 7,000 
public and private clocks, and since 1880 there has never been an interruption of 
this public service which was worth mentioning; nor has there ever any serious 
or even light accident occurred in the works or on the streets, or in private 
houses, and the compagnie have never paid damages to any one for that reason. 
Proofs at disposal. 

Can Mr. Abdank say the same of the trolley, cable and electric works? 

About the complication of the motor, I may say that the 50 moving parts 
of which Mr. Abdank speaks do not exist anywhere else than in his imagination, 
and I wish to add that in my works in Paris I have compressed air motors which 
for 15 years have never been out of order for more than a few hours, necessitated 
by minor repairs. 

The fact that the cost of repairs is not larger, and in fact much smaller on 
compressed air cars is that, as before explained, the Paris General Omnibus Co. 
has ordered 150 new pneumatic cars for running our lines. Although this com- 
pany uses all kinds of systems used in Europe. 

To sum up : Against the interview of the prominent consulting engineer, 
Mr. Abdank, there is the official report of Mr. Metier, Chief Engineer of Paris 
and Seine department, whose authority on the subject cannot be discussed. 

Extract of report of March 19, 1896, on compressed air tram cars. 

"Their auto cars can easily draw one or more carriages attached to them, 
and therefore carry 100 to 150 passengers at a time, and this even on difficult 
lines. Their employ in the very centre of Paris on the "Coeurs de Vincennes- 
St. Augustine" line, where the circulation is extremely intense overall in the Rue 
de Lafayette and around the St. Lazare railway terminus, has not brought to 
light any serious inconvenience. 

These cars are clean, noiseless and do not emit any steam, smoke or odor- 
ous gas. 

They run over the difficult parts of their track at great speed and with the 
greatest ease, owing to their reserve of compressed air, which allows them at any 
moment to give an exceptionally large effort. 

To sum up, experience proves that this system of traction is a good solution 
of the mechanical traction of cars in towns and suburbs. 

(Signed) Hetier, 

Engineer in Chief du Department de la Seine. 

Mr. Abdank, in his substantial interview, insists upon explosions which he 
has seen. "Of course, he does not speak about the number" of deaths brought 
by the trolley, high tension on the trolley wire. But, then, he makes another mis- 
take. Mr. Abdank has never seen any explosion arising from compressed air, but 



USE. 443 

he may have seen explosions of the steam boiler employed on the Mekarski 
trams for the purpose of heating the compressed air (what in my mind is a mis- 
take) and which do not exist on my cars or on any of the motors I have built 
and patented. He cannot have seen any compressed air explosion in France, be- 
cause there never was one, owing to the fact that the air tanks are subjected to 
trials (every lo years) with 33 per cent, suppression and that (contrary to steam 
boilers) their contents do not alter their intra structure to any extent. 

I am willing to prove to this Mr. Abdank with my own tramcars on any 
line in Paris he might choose that : First, the mile car cost will not be larger than 
the overhead trolley; second, that it will be much cheaper than the underground 
trolley and ammutator cars ; third, that the cost of the engines and works is very 
much cheaper ; fourth, that the compressed air is after all very much less dan- 
gerous than electricity. 

Because they have had lately the greatest financial success (owing to the 
fact that American money was behind them) the electricians believe and try to 
make others believe that they are alone in this world, and that they surpassed 
by far all others. It is going a little far in a wrong way. 

There is room in the field of industry for all of us. 

We shall have our turn and then let me tell you that the day we shall be 
on equal financial terms with you, the battle will certainly be short and decisive, 
although, perhaps, not with the result you would like. victor popp. 

Engineer founder of the Cie Rue de la "Air Comprime System Popp." 

Commissionaire of the Ville de Paris for Distribution of Energy and Light. 



COL. PROUT ON PNEUMATIC TRACTION. 

A very interesting and timely article appeared in the New York Times of 
Sunday, July 24th, discussing "The Motive Power of the City Railroads of New 
York," contributed by the editor of the Railroad Gazette, Mr. H. G. Prout. In it 
he notes the progress being made in this city in street railroad work, and indicates 
the change from horses and cable to underground trolley and compressed air; 
we extract as follows : 

"But the whole story is not yet told, and perhaps the present state of the 
art is to some extent only a temporary state. The interest cost and the labor 
charges of the fixed plant for the underground trolley are, roughly speaking, as 
much on a route where there is a car service every five minutes, as where cars 
must be run every forty seconds. There are routes of travel, however, especially 
on crosstown lines, where mechanical traction is desirable for the better public ser- 
vice and to stimulate travel, but where the underground trolley would perhaps not 
pay, or, at any rate, would not pay until there has been a considerable growth of 
passenger movement on such lines. This is still more true of a great many towns 
smaller than New York City. So it is desirable to have a set of independent, 
self-contained motor cars that can run on 'horse car tracks as they now exist, 
and save the cost of the underground trolley construction. Still further, such in- 
dependent, self-contained motor cars could be diverted to any route, and inter- 



444 USE. 

polated between electric or cable cars, and so aid in the development of the logical 
routing of cars according to the demand of the hour. 

"But for such service the steam motor is out of the question, for reasons 
which need not be developed here. The same is true in the present state of the art 
of the electric storage battery motor. The same is probably true of the hot-water 
motor. And so we are brought around to compressed air. There are reasons 
to suppose that a compressed air engine will do street railroad service with ac- 
ceptable speed, reliability and economy. We cannot admit that this is demon- 
strated yet, but there are reasons to suppose that it is true. There is considerable 
accumulated experience in mines, on cotton wharves, and on experimental surface 
lines which justifies such a hope at least, and compressed air motors have been 
improved in design since that experience was begun. There has been no im- 
portant experiment with the latest designs of such motors, and compressed air 
has never been put to the actual work of hauling city street cars in a large and 
responsible way. Such an experiment will soon begin in New York City. The 
Metropolitan Street Railway Company will, within a few months, have a line of 
compressed air motors in service between the ferry at West Twenty-third Street 
and that at East Thirty-fourth Street, by way of Twenty-eighth and Twenty-ninth 
Streets. It will also have a service by compressed air between the West Twenty- 
third Street ferry and the Grand Central Station. This will be a thoroughly 
modern and scientific equipment, and here an actual demonstration will be carried 
out on a large scale. This demonstration will show whether compressed air can 
fill the requirements of speed, power, reliability and economy, as well as electricity 
or steam can do in like situations. The social and financial results of that dem- 
onstration may be very important ; to an intelligent public they may be deeply 
interesting, and so it is worth while to keep close watch of them." 



PNEUMATIC PROPULSION. 



The facilities which the atmosphere offers as a propelling agent, and the 
readiness with which it lends itself to the purposes of locomotion, have for many 
years past caused a considerable amount of attention to be given to the utilization 
of its mechanical properties for facilitating human intercourse. At no time, per- 
haps, was inventive talent more earnestly and more widely engaged in connection 
with pneumatic propulsion than in the early days of railways, when the advan- 
tages which the atmosphere theoretically offers in that connection were seriously 
pitted against those presented by steam. Prior to the advent of steam-worked 
railways in 1830, in which year the Liverpool and Manchester line was opened, 
inventors were hard at work in their endeavors to perfect the atmospheric system 
of railways, as it was then called, and a stimulus was given to their labors by 
the unfortunate death of Mr. Huskisson — the first railway victim — upon that 
occasion. One example of the prior application of the atmospheric principle to 
the propulsion of railway trains was that by Mr. John Vallance, of Brighton, in 
1827, whose experiments were described in The Engineer of May 19th, under the 
heading of "A Singular Railway Experiment." It may prove interesting if we 
supplement that notice by a brief history of pneumatic propulsion, in which ques- 



USE. 445 

tion such an amount of active interest was evinced during what is known as the 
railway mania, that a Select Committee of the House of Commons was appointed 
in 1845 to inquire into the matter. Let us, then, as Lord Jeffrey puts it, call 
back the departed life for a transitory glow. 

It is now nearly two centuries and a half since Papin, in the year 1654, 
suggested the employment of atmospheric pressure against a vacuum as a motive 
power. The suggestion, howeVer, does not appear to have been acted upon, nor 
the principle applied to any practical purpose until it was embodied in New- 
comen's engine, which, of course, was not for purposes of locomotion. That 
application was left for later times to develop ; and, according to the British 
and Foreign Review of April, 1844, the idea of applying atmospheric power for 
the propulsion of land carriages first occurred in a definite form in 1805 to Mr. 
Taylor, of Manchester, the inventor of the first power loom. Although that 
gentleman conceived the idea, he does not appear to have possessed sufficient 
ingenuity to carry it out in practice. He, however, submitted the notion to his 
friends, Messrs. Duckworth and Clegg, two engineers of the time, and although 
they were all three of opinion that the idea was capable of realization, they found 
that the accomplishment of their object was so beset with difficulties that they 
eventually allowed the matter to drop. Taylor's scheme only extended to the 
conveyance of letters and despatches. He suggested that a tube large enough to 
contain a parcel, should be laid down from one town to another, a stationary 
engine being employed at either end to exhaust the tube. 

The subject was then taken up by Mr. George Medhurst, a London engi- 
neer, who, in 1810, published a pamphlet in which he described "A New Method 
of Conveying Goods and Letters by Air." Two years later he published his 
calculations and remarks on the practicability of his scheme. By the year 1827 
Medhurst appears to have further developed his ideas, for in a pamphlet which 
he then published he describes a system in which he employed a tube through 
which he drove a carriage by air pressure in one direction and drew it by 
vacuum in the other. A further development of the system was the employment 
of a tube 24-in. in diameter, within which worked a piston with a piston-rod 
passing upward through a longitudinal channel and connected to a carriage 
running on rails. The piston was to be driven by air-pressure, and the channel 
was to have a water seal. His third suggestion was a combination of the two 
methods, goods being conveyed within the tube and passengers in a carriage 
outside it. Yet another method proposed by Medhurst was to have an iron air 
tube of square section, 4-ft. in area, fitted with a longitudinal flap valve on the top, 
through which the arm of the piston projected, and was attached to a carriage 
running upon the ordinary roadway without any rails. By this modification 
goods and passengers were to be conveyed "at the rate of a mile a minute, or 
sixty miles an hour, and without any obstruction, except at times contrary winds, 
which may retard its progress, and heavy snow, which may obstruct it." How- 
ever wild Mr. Medhurst's system may appear, to him must be given the credit 
of originating the longitudinal valve on the tube, a principle which underlies 
the inventions of nearly all others who subsequently sought to solve the problem 
of pneumatic propulsion with external carriages. 



446 USE. 

Previously to the appearance of Medhurst's last pamphlet, Mr. Vallance 
had, in 1824, taken out a patent for his system of locomotion by atmospheric 
pressure. This system was described by us in the article already referred to, so 
that we need not here do more than observe that it was only a modification of 
Medhurst's first suggestion of a tube through which a carriage was to be pro- 
pelled and drawn alternately by means of a plenum and a vacuum. The working 
model of this railway, 150 ft. in length and 8 ft. in diameter, appears to have 
been the extent of the application of the principle by Mr. Vallance. In 1834 
Mr. Henry Pinkus appeared upon the scene with a patent for a pneumatic rail- 
way, which was on the same principle as Medhurst's fourth modification, with 
the exception that Pinkus proposed to use a circular instead of a square tube, 
and to employ a hemp-and-tallow rope for his continuous valve. The rope valve 
was to be opened by a small friction roller passing under it, and closed by 
another passing over it, both being attached to the carriage about it. In prac- 
tice, however, it was found that on employing a vacuum the rope was forced 
into the tube by the external pressure of the atmosphere, the vacuum being thus 
destroyed. 

The question now was to devise a valve which should neither be blown 
out under internal, nor be forced in under external pressure. And here Mr. 
Clegg took up the running, and in 1839 obtained a patent for a continuous valve 
having a leather hinge, and working in a trough containing a fatty composition 
which was solid at the ordinary temperature, but which was easily melted by the 
application of warmth. This, of course, involved the heating of the composition 
in order to seal the valve in the rear of the opener as the carriage passed onward, 
and this was to be effected by a tubular heater containing burning charcoal. 
Besides the modification of the valve, Mr. Clegg, in conjunction with Mr. Sa- 
muda, improved the armature, which, instead of proceeding vertically from the 
piston to the carriage as in Pinkus' patent, passed through the valve at a very 
low angle — nearly horizontally, in fact — which caused the valve to be only very 
slightly opened. The details of the piston were also materially modified by the 
same inventors, whose names stand out very prominently in the history of the 
atmospheric railway. 

So far the respective inventors only availed themselves mainly of the me- 
chanical properties of the atmosphere resulting from its action on a piston 
working in a tube and connected, through a continuous valve, with an external 
carriage. In 1844 Mr. James Pilbrow pointed out that the idea did not appear 
to have occurred to any one to connect a carriage outside the tube to a piston 
within it without the use of the continuous valve. He thereore patented a 
system which consisted of a circular tube having a longitudinal square chamber 
mounted on the top and opening into it. The piston, which traveled in the 
tube, was connected by an armature with a tail-piece which travelled in the 
square chamber above it. This tail-piece was a double rack, which, as it passed 
along, drove pinions fixed at intervals in pairs on either side of it. The spindles 
of these pinions were continued upward through stuffmg-boxes, their upper 
ends carrying pinions gearing into racks attached to the underframing of the 
first carriage of the train. This system was designed for use either on common 
roads or on railways. Two other modifications of the continuous valve should 



USE. 447 

have a passing notice. They are those of M. Hallette and Mr. Hay, the former 
of whom proposed to close the longitudinal aperture of the piston tube by mean<j 
by one which was free at both edges — a mere strip, in fact, held at the two 
extremities and passing through a forked armature. 

Such are the broad and general principles upon which the construction of 
the old atmospheric railways were based. These principles were applied in prac- 
tice to a limited extent only, although, in some instances, with considerable 
promise of success. In 1840, Messrs. Clegg and Samuda's system was laid down 
experimentally on a portion of the West London Railway, at Wormwood 
Scrubbs. So favorable were the results, that the atmospheric system was 
adopted on the Dalkey extension of the Dublin and Kingstown Railway, and 
this — the first atmospheric railway — was in full operation at the commencement 
of 1844. Its satisfactory working is alluded to in the report of the House of 
Commons Select Committee, to which we have already referred. This success 
led to the London and Croydon Railway Company, in 1844, laying down a line 
of atmospheric railway alongside its locomotive line, and, further, to the 
adoption of this method of working by the South Devon Railway Company on 
a portion of its line. On the latter lines, however, the principle was soon given 
up as unsatisfactory. It was likewise ultimately abandoned on the Kingstown 
and Dalkey line after a trial of several years, when the railway was extended to 
Wicklow. The results of working in all cases clearly showed that the atmos- 
pheric system could not compete with the locomotive with any hope of success. 
The first cost was favorable, but the expense and extreme care necessary to keep 
the tube and its accessories in working order killed it. Thus, the history of 
atmospheric railways can only be considered as a chapter of failures. 

Later times, however, have witnessed a return to the principle, but worked 
out under conditions differing widely from those under which it existed in the 
examples we have mentioned. In the pneumatic system, as iL was now called in 
contradistinction to the old title of atmospheric, a tube of large diameter was 
employed, the carriage itself forming the piston, a useful vacuum being thus 
obtained. It was, in fact, Mr. Taylor's original proposition, which improved 
mechanical appliances enabled engineers to work out in practice. About thirty 
years since the pneumatic system was carried out in various ways. An experi- 
mental line of pneumatic despatch was laid down and worked at Battersea, 
whilst later on a shorter pneumatic passenger railway, embodying advances in 
detail, was constructed and worked for a time at the Crystal Palace. The out- 
come of the experimental working of these two lines was the construction of a 
pneumatic despatch tube by Mr. Ramell in the very heart of London. This 
tube extended from the General Postoffice, St. Martin's-le-Grand, to the London 
and Northwestern Railway terminus at Euston Square. There was a central 
station in Holborn, where was placed the machinery for effecting the transit of 
the trains of carriers. The air motor consisted of a 22-ft. fan, driven by a steam 
engine having a pair of 24-in. cylinders with a 20-in. stroke. The tube was of a 
flattened horseshoe section, 5 ft. wide and 4 ft. 6 in. high at the centre, and had 
a sectional area of 17 sq. ft. The tube between the General Postoffice and Hol- 
born was 1,658 yds. in length, or nearly a mile, the length from Holborn to 
Euston being 3,080 yds., or a mile and three-quarters. The carriers which were 



448 USE. ' 

10 ft. 4 in. in length, were at the ends of the same sectional area as the tube, 
and weighed 22 cwt. each. The trains of carriers were drawn from the post- 
office and from Euston by exhaust, and were propelled to those points by pres- 
sure. Although the system worked very successfully, and was proved to be 
well adapted for the safe and rapid transit of mail bags and parcels, neither 
the postoffice authorities nor the general public availed themselves of its ser- 
vices, and this revival of the atmospheric principle proved a commercial failure, 
and the pneumatic despatch fell into desuetude. It was also proposed to work 
vehicles in the tunnel under the Thames between Smithfield and the south side 
by the pneumatic system, but nothing was done in this direction. So far as we 
are aware, the only form in which the principle has survived is that employed in 
connection with the telegraphic department of the General Postoffice. 

It now only remains to refer briefly to the Select Committee of the House 
of Commons, which was appointed in 1845 to inquire into the merits of the 
atmospheric system, with a view to its general adoption. The committee con- 
sisted of the following members : Mr. Shaw, Mr. Bingham Baring, Lord Harry 
Vane, Sir George Clerk, Mr. Baring, Viscount Mahon, Sir Charles Lemon, Mr. 
Hawes, Viscount Hawick, Mr. Hodgson Hinde, Mr. Morrison, Mr. Pakington, 
Mr. Gibson Craig, Mr. Lascelles and Mr. Wyse. The committee took ample 
scientific evidence, but it was of a very conflicting character. Among the wit- 
nesses in favor of the atmospheric system were some of the leading engineers 
of the day, including Brunei, Vignoles, Bidder, Samuda and Cubitt. On the 
other hand, there were the opinions of equally eminent engineers against it, 
including Stephenson, Locke and Nicholson, all of whom strenuously advocated 
the use of steam. The committee reported strongly in favor of the general 
merits of the atmospheric principle, but wisely recommended that it should be 
left to experience to determine under what conditions of traffic or of country 
the preference to either system should be given. Experience was not long in 
determining in favor of steam locomotion, the disciples of which system 
rapidly increased and multiplied exceedingly. — The Engineer. 



TRIAL OF A NEW AIR POWER CAR. 

The first of the air-power cars for the Twenty-eighth and Twenty-ninth 
street line of the Metropolitan road made an experimental run over the Twenty- 
third street line April i6th last. Among the officials who made the trip were H. 
H. Vreeland, president of the Metropolitan; A. A. McLeod, president of the 
American Air Power Company, which supplies the air motors ; Fred Pierson, 
chief engineer of the Metropolitan ; W. H. Knight, chief engineer of the American 
Air Power Company; M. G. Starritt, assistant engineer of the Metropolitan, and 
H. D. Macdonald, of the Metropolitan. 

The air for these cars will be compressed by the 400 h. p. compressor which 
has been in operation at the power house near the foot of West Twenty-third 
street for some time. The 1,500 h. p. compressor is not completely installed. It 
is expected that it will be in operation within a few weeks, and then the twenty 



USE. 449 

new cars for the Twenty-eighth and Twenty-ninth street line will be started. The 
roadbed will not be changed now. New rails will probably be laid after the air- 
power cars begin their trips. 

The new cars have the same general appearance as the standard electric 
cars used by the Metropolitan road. Some of the experimental cars were run 
on uptown lines among the electric cars and passengers never noticed the differ- 
ence. The compressed air bottles are carried under the seats, three on a side. 
These bottles are made in Germany of a specially prepared nickel steel after a 
process similar to that used by Krupp in making armor plate for battleships. 
The first bottles were made to withstand a pressure of 4,000 lbs. to the square 
inch. This left a margin of safety of only 1,500 lbs. The new bottles can with- 
stand a pressure of 13,000 lbs. to the square inch. The maximum working pres- 
sure will be 2,500 lbs,, and the normal pressure will be 2,200 lbs. 

In the new power house at Eleventh avenue and Twenty-fourth street is 
the 1,500-h. p. air-compressor, which has much the appearance of a marine en- 
gine. This vertical compressor is a great improvement over the horizontal com- 
pressor now in use and will do its work much more economically. The com- 
pressor is about 60 ft. high and has a fly wheel 22 ft. in diameter. It is a four- 
stage compressor. The air is taken in at the rate of 64 cu. ft. to a stroke. In 
the first compressing cylinder it is under a pressure of 50 lbs. to the square inch. 
In the second compressor the pressure is raised to 172 lbs. and the original bulk 
is reduced to 18 cu. ft. In the third compressor the pressure is 589 lbs. and the 
bulk is reduced to 5 cu. ft. Finally, in the last compressor, the pressure is raised 
to 2,000 pounds and the bulk reduced to 1% cu. ft. This is all done in four 
seconds. Compressing air so rapidly heats it to a high degree of temperature, 
and so after each compression, the air is cooled by passing over cold-water pipes. 

The capacity of the new compressor, if the cars were charged directly 
from it, would be eighty cars. By establishing a reservoir of compressed-air 
bottles the capacity will be increased indefinitely. From the compressor bottles 
the car bottles can be charged in two minutes. 

A car will run sixteen miles on a single charge, and the cars, as built, will 
have a speed capacity of from ten to twelve miles an hour. They will be run 
at from five to six miles an hour and will be charged after every other trip. 

The mechanism of the new air motors is very simple. Unlike the first air- 
power cars, in which there was a great number of moving parts, the engines now 
to be used have very few moving parts. The running gear moves in a bath of oil. 

The motors are controlled by the motormen just as the motormen control 
the electric motors now. The platform controllers are only slightly different in 
appearance from those used on the electric cars. 
I The new cars run very smoothly. They are started with very little of a 

jerk. The aim of the Metropolitan's engineers has been, in fact, to produce a car 
which should be as much like the standard electric car as possible, so that the 
running of them would not confuse the employees. ThQ car which made the 
experimental run yesterday was hailed several times by persons who thought it 
was one of the crosstown electric cars. Over in Paris the air-power cars are 
built on locomotive designs. 

I The new cars for the crosstown line will be the first cars to be regularly 
on a street railroad in this country. 



450 USE. 

COMPRESSED AIR STREET CARS. 

In considering the practicability of propelling street cars by pneumatic 
power, we must not lose sight of the fact that for upwards of ten years the 
Mekarski system, which is strictly compressed air system, has been in use at 
Nantes, France, and that this system has also been adopted at Berne, vSwitzer- 
land, and at Vincennes, France. The Popp system, which has recently been 
installed at Vincennes, is an improvement on the Mekarski system, and is 'likely 
to replace it there. There are in this country two systems — the Hardie and the 
Hoadley-Knight. The American Air Power Company, of New York, owns all 
the American rights for these two systems, by virtue of a consolidation of the 
respective interests, except for the States of Illinois and Wisconsin, where the 
Ilardie patents are owned by a company, of which Mr. H. D. Cooke is president. 
The European rights under the Hardie system are controlled by the American 
Air Power Company, but in the consolidation, the so-called Hoadley-Knight pat- 
ents for Europe, were not included. The Mekarski and the Popp system arc 
known as low pressure systems, the air being stored on the cars at pressures of 
from 400 to 700 pounds per square inch. The American systems are high pressure 
systems, the air being stored at from 2,000 to 2,500 pounds per square inch. The 
Mekarski system has demonstrated clearly, that it is not impracticable or extrava- 
gant to use compressed air as a power for tram cars. Mr. Popp in his system has 
gone further than Mekarski ; reducing the weight of the car, and simplifying the 
machinery. It is plain that the Popp system is in advance of any other French 
system, and it does not differ very materially from the best American systems. 

There is little or no radical difference between the Hardie and the Hoadley- 
Knight systems ; the difference being largely matters of mechanical arrange- 
ment, as for instance an English locomotive differs from an American locomotive 
— the cylinders of one are in a certain place and apply the power of the 
drivers in a certain way ; but both are machines built according to our recognized 
ideas of steam engineering practice, and both "go" successfully. We might carry 
this demonstration of the locomotives further, because it really gives a better 
idea of the points of difference between the two American systems. Hardie 
applies his power at the wheel of the car, by means of an engine of long stroke, 
while the Hoadley-Knight system is like the English locomotive, in that the 
engines are between the wheels, the power being applied through a crank shaft. 
Compound engines are used in one case, to compensate for the long stroke and 
early cut-off in the other. The Hoadley-Knight system is more like the best 
practice with electric motors for tram cars, in that the weight of the motors is 
partially placed on the car axle. 

If we admit, that a practical street car can be, and has been designed, using 
compressed air as a motive power, the question arises, why is it not generally 
used for that purpose. The answer to this is, that outside of France, the pneu- 
matic tram car has not, until recently, been favored with that combination of 
mechanical ability and monej'-, which is essential to the success of any mechanical 
enterprise. Mr. Franklin Leonard Pope, a distinguished American electrical 
engineer, now dead, said that compressed air traction would be a success, if there 
had been spent upon it, even a fractional part of the money and brains, that have 
been used in the development of electricity, as a motive power for street railroads. 



USE. 451 

Electricity has always been popular as an investment. Its success in the tele- 
phone, electric lighting, etc., led capitalists to contribute largely toward its use 
for street cars, and it was only after many years of work and expense that the 
difficulties were overcome. Another obstacle, which has up to this time pre- 
vented the more general introduction of compressed air traction, is that it is only 
recently that we have been able to make a safe, simple and light bottle for stor- 
ing the air. The storage system has always been aimed at, both in compressed air 
and electricity, and in order to store sufficient power on the car, it is necessary 
to provide bottles or reservoirs, which cannot occupy much space, which must 
be light in weight, and absolutely safe. This has been accomplished in Germany 
by what is known as the Mannesmann steel tube, which has been adopted gen- 
erally for this purpose. 

The condition of things up to date, is this : " Two cars built under Hardie's 
directions are now running in Chicago, on the North Clark street cable road. 
These cars are similar to two cars built by Mr. Hardie, and operated for twelve 
months at 125th street, New York, Third avenue railroad line. Over twenty cars 
of the Hoadley-Knight pattern have been in operation between three and four 
months on the Twenty-eighth and Twenty-ninth street cross-town line, in New 
York city. This plant was installed by the American Air Power Company, but it 
is under the supervision and has the co-operation of the Metropolitan Street 
Railway Company, New York. Compressed air for street cars has lately been 
adopted in Rome, N. Y., the home of the new Hardie motor. These three cases 
are the only ones, and we cannot safely say, that in either case, the installation 
has passed entirely beyond the experimental stage. It cannot, however, be said, 
that compressed air traction is in the experimental stage, in the sense that one 
would class automobiles. The difference is this : In street car work the im- 
provements are likely to be in details, matters of construction, saving of expense 
of repairs, and such like; while with the automobile we may see radical changes 
in general design, as well as in matters of detail. Compressed air traction is now 
in a condition where it should appeal to commercial interests, where men, who 
are in a position to supply the means and get opportunities to place the cars on 
established roads might make money, provided of course, they employ proper 
mechanical aid and start in at the point which compressed air traction has reached 
to-day. The question of comparative efficiency naturally arises. Electricity 
admittedly is the most successful power for propelling tram cars. It is used 
extensively for that purpose, and has passed beyond the experimental stages; 
but it has certain limitations, and this is where compressed air comes in. There 
are places where it is not permissible to place overhead wires and poles in the 
street, and this is the present field for the pneumatic tram. In comparing elec- 
tricity and compressed air for mechanical traction, we must not forget that the 
successful electric system is not a storage system. Power is generated at a central 
station and distributed along the line. 

Unfortunately a great deal of time and money has been spent upon the 
development of an air system on these lines; that is, the lines where electricity 
is supreme. Engineers now, however, are convinced that the best air system is 
a storage system, and in this air is superior to electricity. Electric storage for 
street cars has repeatedly failed because of expense of maintenance, weight of 



452 USE. 

apparatus, time required to charge, and other obstacles, while it must be admitted 
even by partisans of electricity, that air is easily stored, and that if we are to 
propel tram cars by the storage system, we may turn to air, as the most practical 
power for that purpose. Now this introduces between the storage system and 
the central plant system, which we will not go into here, any further than to say, 
that it is generally admitted that a good storage system will have a large field. 
Each car is independent in itself and is its own locomotive. If it is out of order 
it is taken off and other cars are not interfered with. It does not require expen- 
sive track construction. It calls for an inexpensive plant, and there are other 
conditions, many of which seem to have a strong element that should appeal to 
the popular idea of successful transportation. We have become accustomed to 
such things as wires, poles, and slots in the street, while in Europe and in Eng- 
land in particular, the Bus idea seems to be popular. People prefer individual 
carriages to long trains. The laws restricting placing obstruction in the streets 
are more rigid, and a compressed air storage system, which calls for nothing 
more than two rails in the street, should have a better chance than any other. 

Three systems of mechanical propulsion are to be considered: i. The 
electric overhead trolley. 2. The electric underground trolley. 3. Compressed 
air. The cost of equipping a line, that is the cost of the plant in overhead trolley 
and compressed air are practically the same, and it may safely be said, that the 
cost of operation in both cases is about the same, but that the underground trolley 
is very much higher in first cost, and the figures of cost of maintenance, including 
interest account, etc., will favor compressed air ; so that in one case the cham- 
pions of air may meet the overhead trolley system under equal conditions of cost, 
and without the obstructions in the street, and when competing with the under- 
ground trolley, compressed air has the advantage of lower cost. In connection 
with this important matter of expense the only undetermined point, so far as the 
compressed air system is concerned is the question of durability of apparatus, but 
as all the machinery is built according to common steam engine practice, and as 
in the score of cars installed on the 28th and 29th street lines, in New York, the 
car engines are encased free from dust, and running in oil, the question of 
durability does not appear to be a serious one. Even in this it has to compete 
with the electric engine and attachments, which are mostly of copper, while the 
air engine is all steel and iron. In the Hardie car service on 125th street, New 
York, the average cost per car mile with a two car service running 156 miles per 
day, was about 20 cents. Of this item coal and water represented about one-quai- 
ter, the principal cost being for power plant labor, conductor and motorman, 20 
cents per car mile is not high for a two car service, and might be reduced one- 
half in a large installation. 



COMPRESSED AIR STREET CARS. 

No reference to the subject of Pneumatic Traction is complete without 
mention of the plant which was installed b}'- the American Air Power Company, 
on the Twenty-eighth and Twenty-ninth Street Crosstown lines. New York City, 
page 463. This is the largest pneumatic traction installation that has ever been 



U^E. 453 

attempted and its importance must be recognized. Nineteen cars of the Hoadley- 
Knight pattern have been running for some months, and it is now proposed to 
place some of the Hardie cars on the same line for the purpose of comparison. 
This illustrates the broad view of the subject taken by the American Air Power 
Company, and their determination to test pneumatic traction thoroughly and 
to adopt that system which is best. Fortunately, there is at the head of this 
'company a practical street railroad man, who appreciates the situation, and 
who is reasonably sure to accomplish good results in the present case. It 
is, however, a matter of surprise that a duplicate generating plant has not 
been installed. Electric light installations, electric traction plants and such 
like are almost invariably equipped in duplicate. Pumping plants, and in 
fact wherever the centralized system is used, it has been considered wise not to 
depend on one machine or one set of machines, yet in this case there is one large 
air compressor of 1,500 H. P. capacity, upon which the whole system depends. 
'That the cars should be kept in motion so constantly, notwithstanding the mechan- 
ical difficulties which are sure to arise in the development of any new system, is a 
Jpoint in favor of pneumatic traction, and that the cars may at any time be taken 
oflf and horses substituted is an illustration of the fact that a pneumatic equipment 
^on the automobile plan may be applied to standard horse car roads, and that the 
installation itself is simple and inexpensive. We are heartily with the American 
Air Power Company in this work. We admire the pluck that they have exhibited 
'in spending money to try experiments on a broad scale, and we have no doubt that 
this same spirit will follow them until the road has passed experimental conditions, 
and is an accepted success — a credit to the company and to those who have always 
believed that a good system of running street cars by compressed air would some 
day be brought to the front. 



THE MEKARSKI SYSTEM AT BERNE, SWITZERLAND. 

The main line of the compressed air tramway of Berne, Switzerland, tra- 
verses the town from east to west, and measures 3 kilometres or 2 miles, within 
which, being a single line, it has eight passing places about 66 yards in length 
each. The extensions shown in above map practically cover the city, and reach- 
ing all the principal points of interest or of commercial importance. At certain 
points there are rising and falling gradients of 5 to 6 per cent., and this pre- 
cluded horse traction. Cable traction would have been too costly and the same 
objection applied to underground electric traction, and the local authorities posi- 
tively declined to allow overhead trolleys. Traction by electric accumulators was 
by general consent recognized as a failure. Under these circumstances, conces- 
sions were granted to a company using the Mekarski system in 1889 and put in 
operation. 

Tables of cost show that the cost of operating does not exceed S.gd. per 
car mile. The number of single journeys made per day of 14 working hours, is 
160, equal to about 300 car miles, and the number of passengers in the year 1891 
being 3,140 per day, or 20 per car journey. Seven motors are required; six 



g^Sm Compresied 4ir Tramway. 

mnmrn IjtttnS'ons. 




5^^»,sff^ 



FIG. 144 — PLAN OF BERNE AND SUBURBS. 



PL) AN OP 
Albiiuc/es in Mttres abovt 5 L 

9 O 

pailv^ay SrAPOH 
msrvHU^Mmua passing iStcppmgP/oces p Passing & 



Cemtttiy 
Cninnt: 



506m.%.l.^ 



lace: eastern 

TSPMINUS 




Grvu/ient 
^ metres %. I. 



km.3 /J}&A 



FIG. 145 — PROFILE OF ROAD. 



USE. 



455 



are constantly on the line, and two cars are kept in reserve. Their carrying 
capacity is about 28 passengers. 



THE MEKARSKI CAR AT TOLEDO, OHIO. 

In 1892, the Consolidated Company at Toledo, installed a plant of the 
Mekarski system. The trial trips were made from the power house along the 
principal business street of Toledo, and on tracks used jointly by the horse and 




FIG. 146 — THE MEKARSKI SYSTEM AT TOLEDO, OHIO. 

electric cars, where the traffic was heavy. The car rode smoothly and offered no 
objectionable features to the public. 

The car would run between eight and nine^miles without recharging, and 
was handled with ease and promptness, and all motions were under perfect 
control. 



COMPRESSED AIR MOTORS. 

The compressed air system has been adopted for the 28th and 29th street 
cross-town lines of New York, by the Metropolitan Street Railway Co. During 
the past three years strong efforts have been made to secure for this system a 
permanent franchise for its establishment. 

Extended experiments in connection with the Hoadley-Knight system have 
been conducted by the Metropolitan Railway Company, of which Mr. H. H. Vree- 
land is President. Over eight years ago it was seen that of necessity, some effi- 
cient and economical method of operating street railways in New York would 
have to be adopted, and gas engines, ammonia motors, compressed air, electric 
storage batteries and electricity as a constant current as used in the overhead 



456 USE. 

trolley system, were all considered. New York has stoutly refused to have the 
overhead system, and it was necessary for his company to go ahead and find some 
other system. Eminent engineers were sent abroad and the inquiries brought 
forth some 2,600 replies offering many schemes. Some had merit, but after giving 
them consideration the company was, so to speak, in on the air ; and as Mr. Vree- 
land himself says: "We are latter day saints in the compressed air proposition." 
No such exhaustive research has ever been made in the history of traction. 
It was not conducted solely in the interest of compressed air, but in the interests 
of capital invested in plants, rapid transit for the traveling public, and the comfort 
and safety of patrons. The experiments and tests of steel tubes alone being of a 
most exacting nature. Large numbers of the best tubes were purchased and tested 
to destruction. This system did not dawn on the Metropolitan Street Railway 
Company like a sunburst. It grew and developed, and finally became what it is, 
and its adoption leaves no doubt in the mind of the company as to the success of 
the system both in regard to its efficiency and economy and other advantages 
commonly conceded to compressed air. At the same time the Hoadley-Knight 
system was being tried on the Lenox Avenue line. New York, and on the Ecking- 
ton & Soldiers' Home Railway at Washington, D. C, but the results desired from 
the experiments were so exacting that the chance for their adoption seemed for a 
lime hopeless. 



THE HOADLEY-KNIGHT SYSTEM. 

The compressed air motor cars for this system were designed by Mr. J. 
H. Hoadley and Mr. Walter H. Knight. In general construction the motor 
resembles an electric motor — iron clad, and resting with one end upon the axle, 
to which its crank shaft is geared. 

The unsatisfactory results attending the use of side rods and exposed 
machinery, in connection with the electric motor, were, of course, well known, 
and it was realized at once that in any form of air motor it was essential that 
the moving parts should be enclosed in a case where they could run in oil, free 
from dust, and where they would lubricate themselves continuously without the 
attention of the operator. It also seemed extremely desirable to continue the use 
of standard street car wheels, axles, trucks and car bodies, as these have all 
reached a standardized form which is known to insure the least expense of 
maintenance. 

Owing, also, to the limited intelligence of the motorman, and the necessity 
of more prompt control than is had with steam locomotives, it was considered 
necessary to develop a controller, which could be operated by a single handle to 
perform all the various functions of the controller in their proper sequence, 
without requiring thought on the part of the motormen. These three features of 
iron clad motors, running in oil, standard street railway rolling stock and single 
handle controller, were therefore made the distinctive features of the Hoadley- 
Knight system, which may be described more in detail as follows : 

MOTOR CYLINDERS AND MECHANISM. 

On each axle is mounted an iron clad motor, having two cylinders and 
cranks at right angles. One motor has two high pressure cylinders. 3^/^ ins. 



r 



USE. 



457 



diameter and 6 ins. stroke, and the other motor has two low pressure cylinders, 
7 ins. diameter and 6 ins. stroke. Upon the crank shaft is a pinion, about 9 ins. 
in diameter, meshing into a 23 in. gear wheel mounted on the middle of the axle ; 
the axle is straight, as used for electric motors, and the wheels are ordinary 
street car wheels. The motor consists essentially of a cast iron .case or basin, to 
which the two cylinders are bolted and in which all the moving parts, the piston 
rods, crossheads, connecting rods, cranks, ge.nrs, valve rods, eccentrics and 
reversing mechanism are located. The basin is covered with a lid which can be 
quickly removed, thereby exposing all the machinery for complete inspection. A 





1 


ill 11 > 


f lit 'J 




1 


■1 




- cdiUMBir"''* 

AVENU 


■ 




IIhi^k 


yf^-^r-^^urrr^t^^^^m^^^M 




:flHHi 


kk»^ ^ 



FIG. 147 — COMrKESSED AIR MOTOR CAR. 

sufficient quantity of oil is introduced into the basin to keep the moving parts 
continuously drenched with the lubricant, thus insuring for them the longest 
possible life, and reducing to a corresponding degree the maintenance account. 



/ 



AIR RESERVOIRS AND HEATER. 

The air reservoirs, in the shape of seamless steel bottles, are under the seats 
of the car, and a pipe leads from them to a combined reducing and throttle valve, 
which reduces the storage pressure to the working pressure. The pipe before 
reaching the reducing valve passes around the heater, so that the air can receive 
sufficient heat to prevent freezing any moisture that may be in it. 

The heater consists of a seamless flask charged with hot water under a 
pressure of from 150 lbs. to 250 lbs. 



458 



USE. 



WHAT THE AIR DOES. 

The air on leaving the reducing valve passes through a coil kept hot by the 
heater to a temperature corresponding to the steam pressure of the hot water, 
and is then introduced into the high pressure cylinders, both of which are in one 
motor on one axle. During its passage between the reducing valve and the high 
pressure cylinder, means are provided for injecting a certain amount of moisture 
into the air, this having been found to give certain advantages, as will be 
described later. In exhausting from the high pressure motor, the air is again 
heated and passes through the low pressure motor on the other axle, from which 
it escapes through a muffler into the atmosphere. By having one motor high pres- 
sure and the other motor low pressure, undue slipping of the wheels is prevented, 




FIG. 148 — HOADLEY-KNIGHT COMPRESSED AIR MOTOR TRUCK. 

as when the high pressure wheels slip the low pressure motor gets more air and 
more pressure, and the back pressure from, the receiver tends to stop the slipping. 
When the low pressure motor slips its wheels, it draws down the receiver pres- 
sure and thereby weakens itself, correspondingly increasing the strength of the 
non-slipping motor. The direction of the flow of the air is shown in Fig. 3 where 
R R are the air reservoirs, V the reducing valve, H the heater, M M the motors. 



DURABILITY. 



Twelve months' operation has demonstrated that these motors are highly 
efficient and exceedingly durable, all of the original parts being still in use. The 
manufacturers estimate that, making a liberal allowance for the wear and tear 



V?'/^-^ 



USE. 



459 



that must occur, which, in the case of the more rapidly wearing parts, has been 
measured, the maintenance per car mile can be figured at not more than one 
cent, which compares favorably with that of the electric motor. 

WEIGHT OF CARS. 

The weight of the standard Hoadley-Knight air car is tabulated as follows : 

Car body 6,000 lbs. 

Trucks 4,500 " 

Air reservoirs 3,ooo 

Heater 500 " 

Motors (each 1,500 lbs.) 3»ooo 

Controlling apparatus 400 

Piping 150 " 

Total i7>550 " 

TRACTION AND CONSUMPTION OF AIR. 

The motors are capable of slipping the wheels on a dry rail under a weight 
of 30,000 lbs., and are therefore as powerful as the heaviest electric motor equip- 



R 

























M 


^s^ 


< 






\ 






R 



H 1;^:^- 



M 



FIG. 149 — DIAGRAM SHOWING FLOW OF AIR. 



ment. The total weight is little, if any, more than that of an equally powerful 
electric equipment, and the rigid weight on the axle, to which maintenance of 
track is mostly charged, is considerably less. 

The air consumption of these cars varies from 30 lbs. to 40 lbs. per car mile, 
for a 34 ft. car of the Broadway type. About 11 lbs. of air can be compressed to 
2,000 lbs. per square inch per horse power hour. The cars require therefore, on 
an average a little^over 3 h. p. hours per car mile, which in a modern compressor, 
running on a steady load and pumping into a reservoir of ample capacity, can be 
produced, it is claimed, for one-half cent per horse power hour, including all 
power house charges. To this must be added the cost of the hot water for 
reheating, which is given by the engineers of the system as one mill per car mile. 
The motive power expenses per car mile on this basis are therefore estimated 
as follows: 



46o ttSfi. 

Cost PER CAR MILE OF MOTIVE POWER. 

3>^ h. p. hours at H cent , $-Oi75 

Hot water for reheating ooi 

Maintenance of motor equipment oi 

Total $.0285 

This compares favorably with the best that has been done with electric 
motors. The storage capacity for a run of 17 miles would be 45 cu. ft. 

CONTROLLING THE CAR. 

The Hoadley-Knight motors are controlled by varying the cut-off as well 
as by the throttle, the two being operated simultaneously. This method of con- 
trolling is adopted because it not only gives the highest efficiency, but also gives 
the greatest range of power. A car can be started with a promptness only limited 
by the friction of the wheels on the rails, or may be started with almost imper- 
ceptible acceleration. In common with other air cars, the start is easy and free 
from jerks. 

A forward movement of the single controller handle starts the car and the 
propelling force is proportional to the distance that the handle is moved from its 
starting point, so that any degree of acceleration can be obtained. A backward 
movement to the starting position brings the valve to a minimum cut-off and 
closes the throttle. A still further backward movement reverses the motors and 
opens the throttle to back the car. The inventor claims that anything less simple 
than this is not feasible, or indeed safe, for street car work, and they point out 
as sustaining this view, that the only successful electric controllers have been 
substantially as simple. Of course, with an electric motor the reversing handle 
has been kept separate, as it is undesirable to reverse an electric motor, but with 
an air motor there is no objection to reversing, and there is therefore no need 
of more than one handle on this account. 

HEATING. 

The inventors have made a large and exhaustive series of experiments on 
the subject of the heater. They have tried all the known forms. Their first 
experiment with the Mekarski heater, which is the one generally in use on air 
cars and in which the air is made to pass up through hot water, proved to them 
that such a method is liable to bring excessive quantities of water over into the 
motors, when heavy demands are made upon the air. They also found what had 
not been generally recognized until they announced it, that such a heater, when the 
contained water is under a pressure exceeding that of the air, runs the motor, 
practically as a steam engine, with too much visible exhaust and too little air, 
and that after the pressure of the water in the heater falls belcnv that of the air, 
practically no steam is generated and the air enters the motor practically dry. 
Their experiments with dry heaters showed them that the same economy could 
be obtained with dry heat as with wet, but the heater itself proved objectionable 
and difficult to regulate. This brought about a return to the hot water heater, but 
with certain precautions against admitting the air to the water, which proved 
highly satisfactory. 



USE. 



461 



STORAGE RESERVOIRS. 

Their experiments with air reservoirs have been probably the most exten- 
sive ever made. They have tried large numbers of each of the five different promi- 
nent manufacturers and have experimentally blown up all kinds repeatedly, both 
with air and water, and find that they are all very much alike, both as regards 
strength and character of rupture. They are now using the Ehrhardt flasks. It 
seems to be generally admitted that the air motor would have reached a practical 
state of perfection much earlier, had it not been for the slow development of the 
art of making high pressure flasks, which until the last few years were not 




FIG. 150 — SECTIONAL VIEW OF MOTOR CAR. 



obtainable of sufficient strength to give the desired capacity within a reasonable 
space. 

One of these cars will run 15 miles on a good track on a charge that is 
restricted to a space under the seats, and this could be even increased to 20 miles 
by crowding in all the flasks that the space could allow. 

As the air pressure in the reservoirs is always limited to that which the 
compressor can give, and as the reservoirs themselves are capable of withstand- 
ing nearly three times this pressure, it will be readily seen that the element of 
danger is practically eliminated. There is no possible way in which the air pres- 
sure can be increased to the bursting pressure of the flasks. Furthermore, they are 
protected by a safety pop set up to open at a pressure slightly above that given by 
the compressor. There is no deteriorating influence incidental to their use. There 
has never been an explosion with any of these flasks by air, except when premedi- 
tated, and only then with the greatest difficulty and with apparatus especially con- 
structed at great expense to bring the required force into play. Every flask is 



462 USE. 

tested to 2^/2 times its working pressure before being used. Steam boilers are only- 
tested iH times the working pressure. 

COMFORT AND APPEARANCE. 

The placing of the motor in the middle of the axle and the driving of the 
axle in the middle, by means of the gear, does away with all lateral oscillation, 
so common in side rod motors. 

The car presents an appearance like that of an electric car without the 
trolley accessories, and it is claimed to accelerate as quickly, to run as fast, to be 
as free from vibration, start wuth greater ease, stop with greater promptness 
(owing to lack of momentum of armatures) and to possess in general all the 
advantages of the electric car, without any of its disadvantages. 

It is true that every two hours the cars must be charged, but this is done in 
two minutes and at the end of the line, where it does not inconvenience the 
passengers, and therefore, so far as the traveling public is concerned, is attended 
with no disadvantages. To the street railway man it means practically almost 
no additional expense, as in general a wait of at least two minutes is made at the 
end of the line. 

COMMON ADVANTAGES. 

As compared with the storage battery car, which in its absence from 
dependence upon a distributing system the air motor resembles, the latter is 
claimed to possess the following advantages : 

1. Its storage cells cost very little, comparatively. 

2. They are a permanent investment, requiring practically no repairing. 

3. The reservoirs can be charged in two minutes instead of six hours. 

4. An exhaustion of the battery does not injure it (as with the sulphating 
of the electric battery). 

5. The weight is about one-half. 

6. There is no odor. 

7. There is no corrosive liquid to slop over, or injure operatives' hands. 

8. In case of necessity it can be charged along the line without leaving the 
line. 

Barring fuel burning motors, which seem to be by common consent ruled 
out of the sphere of street service, compressed air stands alone as the only avail- 
able stored force, which suffers no loss or deterioration while stored, which is 
instantly available, which requires no skill to utilize it and which is absolutely 
free from any offensive products. It is due to these practical features that com- 
pressed air has been so successful as a transmitter of force in mining work and 
air brakes, and the same advantages, it is believed by its promoters, will bring 
about its very general adoption for propelling vehicles. 

The expense of installing this system does not differ materially from that 
cf the electric trolley system. The compressed air powep-plant can be installed for 
the same amount as an electric power plant, and the cars, while costing somewhat 
more than the trolley cars, are more than offset, it is claimed, by the expense of 
the trolley line itself. As compared with the underground trolley, there is, of 
course, a saving of the interest and maintenance of the conduit, a sum which 



r..; 



USE. 463 

would in itself exceed in many cases the whole motive power expense of the com- 
pressed air car. 

AIR COMPRESSORS. 

Orders have been given for air compressors with four stage single acting 
air cylinders and intercoolers. They are to be driven by a vertical cross com- 
pound condensing Reynolds' Corliss engine, built by the E. P. AUis Co. The 
compressing cylinders are to be set underneath the engine and are to be built by 
the Ingersoll-Sergeanf Drill Co. The initial cylinder is to be 46" diam. by 60" 
stroke. 



TRACTION AND AUTO-MOBILE. 



Air Plant of the Metropolitan Street Railway Co. in New York. 

A compressed air plant, unusual in almost all of its features, and embodying 
characteristics in design and construction far in advance of ordinary practice, has 
just been completed by the Ingersoll-Sergeant Drill Co. of 26 Cortlandt street, 
New York. The installation was made for supplying the air motors on the cars 
of the Metropolitan Street Railway Company of New York. The station is 
located at Twenty-third street and North River. 

The plant is uncommon mainly for two reasons, its great efficiency in pro- 
ducing compressed air and the high pressure obtained. High pressures with 
small machines are common, but pressures of 2,500 pounds to the square inch in 
1,000 horse power machines are new. In general the machine consists of a duplex 
vertical cross compound engine built by the E. P. Allis Company of Milwaukee, 
vliich has cylinders 32 in, by 68 in. and 60 in. stroke, provided with Reynolds 
Corliss valve gear. With steam pressure of 150 pounds, furnished by Babcock & 
Wilcox boilers and 40 revolutions per minute the hofse power is 1,000. The shaft 
is of hammered iron 22 inches in diameter outside of the journals, 20 inches 
diameter in the bearings, which are 36 inches long. The fly wheel placed between 
the cylinders, as shown, is 22 feet in diameter and weighs 60 tons. The engine is 
mounted upon brick piers, and directly underneath it is placed 

THE AIR COMPRESSOR. 

This machine is of the four cylinder type, the low pressure cylinder being 
46 inches, the first intermediate 24 inches, the second intermediate 14 inches, and 
the high pressure cylinder 6 inches in diameter, the stroke being common with the 
engine, 60 inches. All of these are single acting. I'he free air capacity per 
revolution is 56.735 cubic feet; capacity at 40 revolutions 2269.4 cubic feet, and the 
free air capacity at 60 revolutions is 3404.1 cubic feet. The approximate pressure 
in the first cooler is 40 pounds, in the second 180 pounds, and in the third 850 
pounds, the final ^approximate pressure in the after cooler being 2,300 pounds. 

The compressor pistons are arranged in pairs vertically in line beneath the 

kani cylinders, as is shown in Fig. i, the initial and first intermediate air cylinder 

being below the low pressure steam cylinder, while the second intermediate and 

high pressure air cylinders are below the high pressure steam cylinder. Motion 




FIG. 151— THE VERTICAL FOUR STAGE HIGH PRESSURE AIR COMPRESSOR USED FOR SUPPLYING 
POWER FOR STREET CAR SERVICE ON THE 28th AND 29TH STREET LINES, NEW YORK. 



USE. 



465 



is transmitted from the steam engine cross heads through distance rods for each 
cross head to a cross head attached to the air cylinder piston rods. 

The inlet and discharge valves of the initial air cylinder are of the "Me- 
chanical" tA^pe and of a special design. These valves are shown at K Fig. i. Air 
is admitted to the top of this cylinder through the supply pipe a, and leaves the 
cylinder through the pipe a by which it is conducted to the first inter cooler E. 
From the cooler E the air flows through the pipe b' to the lower end of the first 
intermediate air cylinder B from which it passes through the pipe b to the second 




FIG. 152 — BATTERY OF STORAGE TUBES, IN WHICH AIR IS KEPT AT 2,500 POUNDS 
PRESSURE, AND FROM WHICH THE CARS ARE CHARGED. 



intercooler F. From here it passes to the pipe c to the upper end of the cylinder 
C from which it passes to the third cooler G and from here through the pipe c' to 
the lower end of the cylinder D and from this through the pipe c to the final after 
cooler H, from which it is led through the outlet f to the storage bottles. From 
this it will be seen that the air passes through the upper end of the cylinder A, 
lower end of cylinder B, upper end of cylinder C and lower end of cylinder D and 
in its passage between each passing through one or the other of the coolers. 



466 USE. 

The intercoolers employed are of two different designs, the two coolers for 
the lower pressures consist of a shell enclosing a nest of vertically arranged cool- 
ing pipes through which the air passes going from one cylinder to the other, the 
coolers for the higher pressures consist of a shell enclosing a pipe coil, the air 
passing through the coil from one cylinder to the other. In providing a cooler for 
the lower pressures where great cooling surface is required on account of the 
large volume of air to be cooled, it was considered proper to provide tubes, but in 
dealing with the cooler for the higher pressures, coils were substituted so as to 
dispense with as many joints as possible. The coolers are arranged so that in case 
a leakage of air from the cooling pipes into the shell or casing that this air rises 
with the circulating water up to the operating floor of the engine room and is 
discharged through a sight discharge pipe under the immediate care of the 
engineer. All the piping from the first air cylinder and through the entire com- 
pressing plant is made of copper. 

What may be called an auxiliary governor controlled by air pressure is 
provided to act upon the governor of the steam engine. This consists of a 
weighted lever which is operated upon by a small piston which in turn is actuated 
by the air pressure. If for any reason the pressure should become excessive the 
lever is lifted, when it opens a valve admitting air to a device on the governor so 
designed as to reduce the steam supply and to all practical purposes throttles 
the engine. 

Some idea of the massiveness of the machine may be obtained from the 
bare statement that it is 60 feet in height. It will be employed exclusively^ for 
supplying air to the air motor on the street railway cars. It may be stated that 
since their first trial several months ago the air motors of the Hoadley-Knight 
type introduced on the street railroad line have given good results. 

Compressed air for the purpose of traction by this system is generated and 
collected in a manner similar to the manner of generating and collecting gas, and 
the necessary means for the storing of compressed air at high pressure consist in 
the collection of numerous bottles connected together in series or manifolds 
whereby the different sections of storage can be cut out from one another. In the 
storage system erected at the Twenty-fourth street compressor station there are 
about 600 bottles. These bottles are all tested to a pressure of 4,000 pounds per 
square inch, and are used to store air at a pressure of 2,500 pounds per square 
inch. There is no wear and tear on these storage bottles other than can be made 
good by painting from time to time. The storage bottles are connected together 
with proper pipes and valves and communicate with several charging stands in the 
car house. The cars can be charged with compressed air at 2,500 lbs, pressure in 
about two or three minutes' time. The method of connecting the compressed air 
pipe to the car is similar to the way in which the breach is locked to a gun. 

The charging nozzle is introduced in the charging orifice and a partial turn 
[^iven to the charging nozzle locks the charging nozzle in the charging orifice, 
then the main valve is opened admitting air to the car. The reheater is charged 
with steam in a similar manner. 

The charging nozzle of the reheater is provided with a vent hole through 
the centre whereby the coupling of the charging nozzle to the charging orifice 
makes communication for the steam to enter the reheater and for the vent to go 
out from the reheater with the one charging nozzle. In the recharging of the 



USE. 



467 




FIG. 153. 



468 



USE. 



compressed air cars the first operation is to connect the steam charging nozzle 
to the reheater and then to connect the compressed air charging nozzle to the 
charging orifice. This operation takes from three to four minutes. These 
compressed air cars are equipped with six Mannesmann tubes, three on either 
side of the car under the seats and making a storage capacity of about 45 cubic 
feet. This storage capacity will enable the car to travel distances of about fifteen 
miles. The reheater is hung to the car body and lies between the two motors. 
It is a seamless welded tube and holds about six cubic feet of hot water. The 
air from the storage reservoir passes by a reducing valve and is reduced from a 
varying high pressure to a constant normal pressure. A throttle valve is on the 




FIG. 154- 



-BIRDSEYE VIEW OF THE MOTOR AND TRUCK OF THE AMERICAN AIR POWER 
company's system of STREET CAR PROPULSION. 



Other side of the reducing valve controlling the admission of the air to the 
heater and thence to the motor. When the throttle is opened the air passes 
through a coil in the reheater and before it enters the reheater a spray of water 
is introduced into the air and passes through the coil in the reheater on to the 
motor. 

The motors are of the compound type, high and low pressure, the air enter- 
ing the high pressure and doing work expansively and then passing over to the 
low pressure motors and doing more work, and then being exhausted to the 
atmosphere through a muffler to prevent noise. The motors are of the enclosed 



fV^ 



USE. 



469 



type, similar to street railway electric motors, and are applied directly to the car 
axle. They consist of the two high pressure motors four in. in diameter by six in. 
stroke, and two low pressure motors eight in. in diameter and six in. stroke. 
Mounted on the crank shaft in the motor is a pinion which'engages in a spur gear 
fixed to the car axle, the reduction is about 2^/4 to i. The motor cylinders are 
equipped with piston valves which are controlled by a movable eccentric of the 
wedge type. These eccentrics are connected directly to the crank pins of the 
motor and the wedges for operating them connect it to a common lever extending 




FIG. 155 — CHARGING APPARATUS FOR AIR AND STEAM. THE STEAM BEING USED FOR 

RE-HEATING PURPOSES. 



icross the motor casing, and by means of this wedge eccentric the motor is 
adapted to run in the forward or backward motion and any degree of cut off for 
the control of the motor can be obtained. This valve mechanism is connected 
directly with the throttle valve and is so arranged that the motor man in manag- 
ing his car has but one lever to control. The motor casings are partially filled 
with oil, so that when the motor is in operation the oil is thoroughly broken up in 
small particles, thereby properly lubricating all moving parts. These cars are the 



470 



USE. 



standard of the Metropolitan Street Railway Co. They are built on the standard 
Brill truck of eight feet wheel base. 

The application of these compressed air motors to street cars is similar to 
the application of electric motors, that is to say the weight of the motor is par- 
tially on the car axle. All the other parts of the system, as the storage bottles and 
the reheater, are mounted to the car body and all under the effect of the car 
springs. 

The Mannesmann bottles are all tested to a pressure of 4,500 lbs. per square 
inch, and as they are filled with air at a pressure of 2,500 lbs. per square inch, 
there is a factor of safety of about 2. The question is frequently put as to the lia- 
bility for these tubes to explode. When the tubes are filled with the air at 2500 lbs. 
per square inch there is no practicable way whereby the pressure can be increased, 
in fact, the only thing that can happen is for the pressure to decrease. This con- 
dition is greatly different from any other engineering problem. A bridge is built 
over a stream or anything else to carry the public and designed to carry a certain 
load. Bridges so made do very well but it sometimes happens that they get over- 
loaded and break down. This cannot happen with the compressed air bottle. 
Should a car collide with another car or something similar the worst that could 
happen to the bottle would be to squeeze it together a little bit and then it would 
relax to its normal condition. Possibly one of the small pipe joints might start to 
break, but no serious explosion or destruction is likely to be caused by a collision. 



New York, Sept. 13, 1899. 
Editor Compressed Air: 

One of the New York daily papers has commented quite severely on the 
Compressed Air Street Railway System now being operated on 28th and 29th 
streets, New York City. The main objection offered is the dropping of oil along 



tdge turned on Shdft 
ro throw off Oil. 



FIG. 156.' 



the track. This is unquestionably a fair objection and one which must be re- 
moved before the system will give complete satisfaction. It is, however, a 
trouble which appeared in the earlier experiments with electric motors and 
caused a great deal of annoyance and expense and some criticism. In the case 
of electric motors the trouble was remedied by adopting an enclosed motor and 
gear case and adopting a form of bearing which prevented the oil used in Mie 
gear cases from leaking out of the bearings. It is, of course, apparent that oil 
will, from capillary action, work through the bearings of the oil-filled case to the 



USE. 



471 



outside, and unless some means is arranged to catch this oil, it will be thrown 
off and collect under the car body and along the track. In the case of the air 
motor as used on the 28th and 29th street line, the reduction gears run in oil 
to reduce friction and prevent noise. As far as I am able to determine, no pre- 
cautions have been taken to prevent this oil^ working through the bearings as 
described, and it would seem advisable for the railroad company to adopt the 




Cup f/an^e cdst 
fastened to 
bearing' 



FIG. 157. 

simple method used by the manufacturers of electric motors, a sketch of which 
is sent herewith. 



THE POPP SYSTEM. 

The several papers which have been published serially in this paper, written 
by Mr. Victor Popp, of Paris, are worthy of serious study by those interested in 
the practical application of compressed air. Mr. Popp writes from a practical, as 
well as a theoretical standpoint. His large experience and the success of his 
work entitle him to the position which he holds as a recognized authority on this 
subject, and we doubt that there has been published anywhere so important a 
series of papers giving such practical information as those written by Mr. Popp. 
We have been accustomed to read highly technical matter on this subject, and 
engineers are prone to deal in formulas and calculations, which are interesting 
enough to theorists, but which really bring no practical results. Mr. Popp, with- 
out neglecting theory, treats of the subject in so practical a manner that his 



472 



USE. 



theoretical deductions are easily tmderstood, and they add to the value and 
reliability of the practical information which he gives. 

Professor Riedler has said that Mr. Popp was the first to successfully use 
the reheating system with good results. We think it quite true that the first prac- 
tical reheater was used in Mr. Popp's system, in Paris. A great many desultory 
experiments were made, and reheaters of many kinds were put in use in America ; 
but Mr. Popp's heater was the first one to give practical results, and to be applied 
in continuous service. Mr. Popp is also the author of a very interesting system of 
Pneumatic Traction, which has recently been introduced into France. Two trams 
of the Popp system are running at Vincennes, in competition with the Mekarski 
cars. It is generally known that the Mekarski cars have been running in France 
for more than ten years, and that they have been giving good practical results. 
The Popp cars appear to be superior to the Mekarski in many ways, they are 
lighter in weight, more simple in construction, and under easier control by the 
motorman. Besides these advantages, the Popp car is reversible, it being simply 
necessary to transfer the brake-wheel and certain light parts from one end of the 
car to the other, and start the car in the opposite direction. An important point 
of difference is in the system of reheating. The Mekarski car using the "wet" 
system of reheating, while Mr. Popp applies the "dry" system. In the wet system 
it is well known that water heated by the introduction of steam, is used for warm- 
ing the air. and that the air passing through this hot water, carries with it a cer- 
tain amount of moisture. Apart from the expense involved in producing heat 
through steam, the wet system has other disadvantages, viz. : the tanks occupy 
space, time is required to heat the water at the end of the line, and in a long run 
the temperature is considerably lowered. Another disadvantage, and one which 
is seldom touched upon, is that wet air, like wet steam, helps to destroy the cylin- 
ders, pistons, and other moving parts. Though the air is hot when it enters the 
cylinder, it is soon cooled below the dew point by expansion, and deposits its 
moisture; so that what at first appears to be an advantage in vapor from water 
mixed with air, is only an advantage while the air is hot, and is a distinct disad- 
vantage when condensed and left in the cylinder. Water in cylinders wipes away 
the oil, and is a source of destruction howsoever clean the water may be. It is a 
mistake to suppose that water is a lubricant ,•* on the contrary, it interferes with 
lubrication. Mr. Popp overcomes these difficulties by the introduction of a small 
dry heater, burning coal, charcoal, or coke, the draught for which is made by the 
exhaust from his motor. It is always easy to get coal and coke, and the quantity 
used in a tramway heater is so small that it does not materially aft'ect the cost of 
operation ; besides, it is difficult to overestimate the value of reheating. 

On this subject, we would refer our readers to recent mmibers of this little 
magazine, more especially to the October number, in which a description is given 
of Mr. Popp's heater, together with figures and data based on experience. Mr. 
Popp gives us the figures to show that, according to Professor Guttermuth's ex- 
periments, one kilogram of combustible will, under good circumstances, give up 
as much as 5,600 calories in an air heater. This result Mr. Popp goes on to say 
"being superior by at least 500 per cent, to the results obtained by the best triple 
expansion compound condensing engine," and again it is interesting to note the 
staloment made by Mr. Popp that "the amount of coal required for reheating 



r^ 



USE. 473 



air for large motors being 0.2 of the pound per h.-p. hour." This, as engineers 
will see, is about six times more efficient than the best results obtained m pro- 
ducing compressed air through our best Corliss engine system. 



In an article which follows that of Mr. Popp, in the October number, some 
interesting figures on this subject are given by Professor Nicolson, m a report 
on trials made at Magog, Quebec, to test the economy effected by re-heating 
compressed air. This article is also worthy of very serious consideration and 
study. It impresses us as practical, and as of value as a matter of reference. 
The system which Professor Nicolson refers to, is the well-known Taylor system 
of compressing air by the flow of water. This had been in successful operation 
at Magog, and as a water power installation on a large scale, it is a success of 
the highest scientific interest. Professor Nicolson gives us some figures showing 
comparisons between the wet and the dry systems of reheating, concluding by 
saying that wet heating is inferior to dry heating. He quotes Professors Riedler 
and Guttermuth as having obtained an additional power in air motors for every 
three-quarters pound of coal burnt to heat the air, and goes on to say that this 
is an economy "far surpassing that of any prime motor in existence." We think 
this latter statement will not be questioned by engineers, nor does any one doubt 
the correctness of the results obtained by Professors Reidler and Guttermuth ; 
these results, as remarkable as they are, are capable of considerable improvement 
when a perfect reheater has been designed. Thus far, our best reheaters in prac- 
tical service do not convert the maximum amount of fuel into expansiveness of 
the air, while it is quite within reason to expect almost a complete conversion of 
the theoretical efficiency of a pound of coal into expanded air by a thorough sys- 
tem by which all the heat produced by burning the coal is transferred into the 
air. Then again, we have further possibilities in reheating air because the science 
is likely to develop into compound engines using air at different pressures, and 
reheating between each stage. 

So economical in results is the system of using reheated air, that it is quite 
possible to restore at very little expense in fuel all, or nearly all, the power ex- 
pended at the generating station, and lost through the heat of compression, fric- 
tion, leakages and other conditions that will always exist in a compressed air in- 
stallation. The encouraging point about the use of compressed air, is that, not- 
withstanding these losses, there still remains boxed-up a cold elastic substance, 
which is capable of taking up heat in large quantities and expanding in propor- 
tion as the heat .is applied. In no other power are there such opportunities, be- 
cause we must all admit that in every other known form of power it is impossible 
to restore energy lost at the generating station or along the line, except at an 
expense that makes it prohibitive. It is often said that compressed air is only a 
means by which power is transmitted, and is not a power in itself. We now see 
that through reheating, compressed air is justly entitled to be called a source of 
power, and not merely a means of transmission. 



474 USE. 

REPORT ON THE NEW HARDIE AIR MOTOR CARS NOW IN USE 
ON THE 28TH AND 29TH STREET LINE, NEW YORK CITY. 



September i8th, 1900. 
Mr. Clark, No. 621 Broadway, New York City, N. Y. 

My Dear Mr. Clark : — Agreeable to your wish, I have the honor to report 
to you that I have inspected the Hardie Air Motor, now in service on 28th and 
29th Streets, New York City, 

Motor: A four wheel Air Motor, about 20 horse power. Cylinders, 6^ 
inches by 12 inch stroke. Four driving wheels, 26 inches in diameter ; steel tired. 

Rigid wheel base, 8 feet. 

Weight of iron frames, pedestal jaws, boxes, shoes, wedges and binders — 
all in good proportion, and same as the running gear of a steam locomotive. 

Cylinders well secured to frames. Guides, Crossheads, Linkvalve motion 
and valve gear with independent cut-off. All parts easily to adjust and cared 
for. Wheels are connected by Crankpins, parallel rods and main rods to cross- 
heads and pistons. 

Frames: The frames are extended 6 feet and 9 inches from center of 
pedestals, making a total length of frame 21 feet and 6 inches. 

Heater Tank: A heater tank, or "Cylinder" is placed between frames, as 
also are the air storage tanks and reducing pressure valve. All pipe connections 
are made in a good and workmanlike manner. 

The storage tanks have a capacity of ssJ^^ cubic feet of air, which is com- 
pressed to 2,500 pounds per square inch. 

Car body, 22 feet outside, with platform at each end, 4 feet. 

Total length over all, 32 feet. 

Seating capacity, 30 persons. 

Total weight of Motor Truck, 11,000 pounds. 

Total weight of car, ready for service, 19,000 pounds. 

The body of car is fastened to Motor framing by elliptic springs, and 
Motor Frame rests on saddles and springs, which give the car easy motion over 
rough and uneven tracks. 

Under side seats in car are placed air storage tanks, which are connected 
by piping to air storage tanks on Motor Trucks. 

Also Pintsch Gas Tanks, from which the cars are well lighted by night. 
This light, so well and favorably known, needs no further comment. 

On each platform is placed the operating mechanism consisting of revers- 
ing lever, throttle lever, air brake lever hand brake, and valve for shutting off 
air storage. The simplicity of this operating mechanism makes it easy to con- 
trol the movement of the car, and in appearance, that of electric motors. 

The air brake is especially a new device, and commendable. It is easily 
operated, and very effective in braking power. It is noiseless and instantaneous, 
both m application and release— no noise or hissing of air, as in other air brakes. 
All other air brakes that I know of do not release until the brake cylinder is bled 
It IS a special feature of this brake that it releases first, and bleeds afterwards. 
The same air which applies the brake releases it without the aid of a spring, and 
without noise. 



USE. 475 

I will here state that the air brake valve performs other functions in addi- 
tion to operating the brakes. One is to start the motor from a state of rest, and 
the other is to rapidly accelerate the speed of the motor from a state of rest to 
full speed. 

It will be readily understood that, with an engine having two cylinders 
with cranks at right angles, if the cut-off is earlier than half stroke one crank 
may be on the dead centre and the other on the quarter, but cut off, the engine 
will not start. By moving the lever one position in the opposite direction from 
that required to apply the brake, air is admitted from the brake valve directly 
through the main valve, which starts the engine, instantaneously and positively. 
By moving the brake lever still another position, air is bled from one side of a 
piston attached to the valve stem of the reduction valve, so that pressure acting 
on the other side of this piston assists the valve spring to hold the valve open, 
requiring a higher pressure to close it against the combined action of the spring 
and piston. This high pressure is just what is wanted to enable the motor to 
accelerate rapidly from a state of rest. As soon as the motor has acquired the 
necessary speed the motorman moves the lever to the normal running position, 
restoring the pressure behind the piston so that it is a gain in equilibrium, and 
the motor again is operated under the normal pressure. 

The whole mechanism is ingenious and novel, and may be characterized 
as admirable. 

The hand brake is similar to the street car hand brake, and is only an 
alternative in case of the air brake failing — and only to be used to complete the 
balance of the trip. 

The car is nicely painted on the exterior and interior, and resembles in 
appearance the electric car. 

The motor trucks are not exposed, being shielded by a lattice screen below 
the car body. 

The air compressing station is situated at the foot of West 24th street, 
New York City. 

A 1,200 horse power engine, operating four stage Tngersoll-Sergeant air 
compressors, with a capacity of 56^ cubic feet of free air per revolution com- 
pressed to 2,500 pounds per square inch. This air is stored in reservoirs in the 
car shed, from which the reservoirs on the cars are charged to the same pres- 
sure. The charging a car with air, and the hot water tanks, or "superheater" 
requires an average of two minutes. The car is then ready for a fifteen (15) 
mile run. 

I find that there is very little noise when the motor is first started, and 
after starting, entirely noiseless, and that there is no jerking motion. The 
motor is clean, and free from dust and oil. 

The motor and car herein described, I think, will prove in service to be 
practicable, and each car with its power is independent. The air storage is auto- 
matically reduced to a working pressure of 150 pounds per square inch. Having 
the storage at 2,500 pounds, the reduction valve governs this pressure through 
all stages until it is reduced to 150 pounds. 



476 



USE. 



I think the Hardie Motor will prove economical in maintenance, as all its 
wearing parts are well constructed and easily accessible for adjustment and 
repairs. 

I have looked over the reports made by experts, and have every reason to 
think they are correct — showing compressed air power to be cheaper than elec- 
tricity or any other motive power. 

Safety: The air storage tanks are all tested to a much higher pressure 
than the pressure they are stored with for service. 

It is my opinion, judging from the construction of these storage tanks, 
and the tests they are put to before they are placed in service, that there is no 
possible danger of explosion, and they should prove to be practically indestruc- 
tible. 

I see no reason why the Hardie motor should fail to prove itself a success 
as to economy, safety and efficiency. Respectfully submitted, 

W. L. HOFFECKER. 



THE JARVIS PNEUMATIC CAR. 

At Detroit, Mich., in 1892, inventor Samuel E. Jarvis made experimental 
trips with a low pressure car on a mile of track. Air was compressed at one 
end of the line and was delivered to a 6-inch main which was laid just under 




FIG. 158 — TPIE JARVIS SYSTEM. 

the pavement in the centre of the track for the full length of the road. The 
motor got its power from this pipe. The car carried four cylindrical tanks. It 
was able to run at the rate of fifteen miles an hour. 

The tanks were charged at street crossings or other places where it was 
necessary to make stops. 



HI 



USE. 



477 



THE VINCENNES-VILLE EVRARD COMPRESSED AIR TRAMWAY. 

In 1888, a tramway was constructed from Vincennes to Ville Evrard, and 
the Mekarski compressed air cars put in operation. The system then employed 
consisted of a motive fluid, not cold and dry compressed air, but a mixture of air 
and steam. This was done because it was known that compressed air when ex- 
panding produced a strong depression of temperature, the steam in giving up its 
heat limits such depression, which is the cause of a great loss of power. Air 
was used under low pressure. A regulator was interposed between the com- 




FIG. 159 — PLAN SHOWING AN AIR PIPE LINE IN PARIS. 



pressed air reservoirs and the engine; (i) a heater that serves for obtaining the 
motive fluid, and (2) a regulator or expander that serves for sending the gas- 
eous mixture to the cylinders under a constant pressure, whatever be the pres- 
sure in the reservoirs. The results obtained show it to be a most economical 
process. An examination of the figures for several years showed that animal 
traction cost from 23 to 15 cents per mile, and steam propulsion cost 20 to if, 
cents per mile, and compressed air propulsion at Nantes cost less than 12 cents 
per mile. 

The line mentioned is 58 miles in length. It runs through the Bois de 
Vincennes, passes near Fontenay-Sous-Bois, goes to Nogent-Sur Marne and 



478 



USE. 



Perreux, touches Neuilly-Sur-Marne, and finally ends at the departmental asy- 
lum of Ville Evrard. It has gradients reaching half an inch to the foot. This 
same system has been in operation at Nantes for nine years previous, and satis- 
factory results had been obtained. 



THE POPP-CONTI SYSTEM. 



The Popp-Conti system which is in use in Saint-Quentin, Angouleme and 
Lyons, France, is described as follows : 

It is a low pressure system, and at starting the tramway is charged with 
a sufficient quantity of compressed air to enable it to run for four kilometres, 





■ 




piiiliHilili:' 

^^^P^*' •'* ^WR' .'^^;i^' ««■*;* h»Mas^ tesSB* !_ti;i.x4 f^.^^^Y|t;??» : 


m 


f • ' 


> iJ^^^^^^H^^^H^^^^H^I 


m 


-.-^-^^: 



FIG. 1 60 — THE POPP-CONTI SYSTEM. 



after which distance it becomes self-charging, and by the following ingenious 
device : 

Before each waiting station the rails are provided with a pipe which is set 
in the hollow over which the wheels pass. That causes a smaller pipe to spring 
from the ground and enter a hydraulic joint placed under the tramway, by which 
means the receivers installed there are connected with the underground conduit. 
The amount of compressed air received in a few seconds is sufficient to propel 
the tramway for a further distance of four kilometres. This done, the little, 
pipe re-enters the ground and is automatically covered by an iron plate, over 
which men and horses alike may pass with perfect safety. 



USE. 



479 



Such prominent engineers as MM. Huet, Boreux, Humblot, Petsch, Mon- 
merque, etc., who were present at several tests, congratulated M. Victor Popp 
upon the success of his system. 



THE HUGHES AND LANCASTER CAR. 

In 1890, Messrs. Hughes and Lancaster, of Chester, England, operated a 
tramcar by compressed air at a pressure of 155 lbs. to the square inch. The air 
was carried in vessels attached to the car, and the supply of air was renewed at 
intervals on the journey by an automatic valve on the car. A corresponding 




'ELEVATION OF C«B, SHOWINO VALVE AND COULTER. 



FIG. 161 — THE HUGHES AND L.\NCASTER SYSTEM. 

valve is placed on an air main which is laid the whole length of the tramway 
where the road had heavy gradients, and where the traffic was exceptional they 
were placed at smaller intervals. Air could be taken whenever required. This 
mode of collecting energy en route has its own friends, and is said to be eco- 
nomical. 



THE FIRST STREET RAILWAY. 

The first ancestor of the street railway was the tramway. Tramways were 
first introduced in the coal mining districts of the North of England, between 
the years of 1602 and 1649. They consisted of parallel lines of wooden trams 
or beams, pinned down to the ground, with flanges on them, and not on the 
wheels as now. Coal wagons were drawn to and fro along these flanged trams 
from the coal pits to the shipping ports. The first use of iron on these tram- 
ways was in 1767, when cast iron plates were nailed down on timbers to protect 
them where they wore out the fastest. The plates or rails were cast in sections 



48o 



USE. 



five feet long, four inches wide and an inch and a half thick. All iron rails were 
cast until rolled wrought-iron rails were introduced in 1820. The width of the 
tramways was about four feet, eight and one-half inches, because that happened 
to be the usual width of wagon tracks in that region. Horse railroads of a 
crude type were in use in England in 1805. We find in that year five were char- 
tered by act of Parliament ; sixteen were chartered in 1815, and thirty-two in 
1825. After that it seems to have become a lost art in England, as the modern 
tramway was not employed until 1832, at which date, the first street car line for 
passengers was built on Fourth Avenue, New York, llie system was not con- 




FIG. 162 — THE MEKARSKI SYSTEM. 

sidered a success, however, until twenty years after, or in 1852. when a second 
line was constructed, and from this date the system spread rapidly throughout 
the United States. In i860, George Francis Train attempted to introduce the 
present type of street railway into England. 

A line was laid on one of the roads of Birkenhead, and the following year 
a temporary footing was obtained within the suburbs of London. Owing to op- 
position created by prejudice, the system was extinguished for some years, and 
was not successfully revived till 1868, when by act of Parliament, permission 
was obtained for a system of horse railroads in Liverpool. Following this, thert 
was a rapid development of horse street railroads on the continent and other 
parts of the civilized world. 



WnW^ 



■p**i II T^-jr.-T^- ~ 7-» V. 



USE. 



481 



RECENT EXPERIMENTS IN COMPRESSED AIR MOTORS. 

In 1880, it was thought Col. Beaumont, R. E., of England, had effected a 
locomotive that had mastered the problem of compressed air for traction pur- 
poses. The construction of the engine was based upon the principle of utilizing 
the entire power stored up in compressed air, no matter how high the pressure 
should be. This was effected by admitting the air into successive cylinders, 
having different areas, commencing with the smallest, and in making provision 
by which, as the pressure fell in the reservoir, the consumption of air can be 




FIG. 163 — TRIAL OF THE BEAUMONT COMPRESSED AIR MOTOR AT WOOLWICH 
ARSENAL, ENGLAND. 



increased. In appearance the engine differed from an ordinary locomotive, the 
absence of a funnel or other outlet for smoke or steam being a prominent de- 
parture. 

Col. Beaumont was allowed by the British Government to experiment in 
the Royal Arsenal, Woolwich. 

A difficulty met with in the Beaumont method, was the tendency to pro- 
duce extreme cold, which became condensed and frozen on the wo.fking parts. 
Reports of tests, however, show that very good results were obtained. 



482 USE. 

COMPRESSED AIR FOR STREET RAILWAY OPERATION.* 

"Compressed Air for Street Railway Operation" is the subject assigned 
to me for treatment in this paper, and I find it difficult to place all the facts for 
an intelligent consideration of this subject before this convention in the twelve 
minutes allotted to me. 

The question of liquid air was also coupled with this subject, but I do 
not deem it necessary to touch on this question more than to say that nothing 
has been accomplished in the manufacture of liquid air which will warrant its 
consideration as a factor in the operation of street railroads at this time. The 
present method of its production is to start with compressed air at 2,000 pounds 
pressure, and by expanding many volumes of- air at this pressure, thereby pro- 
ducing intense cold, to liquefy a small volume of air. The only advantage which 
liquid air has is the small form in which it can be stored, 800 feet being com- 
pressed into one ; but, on the other hand, as in this form it is the ice of air, the 
additional cost of heat necessary to return it to ordinary air for use in cylinders 
adds unnecessary expense. In other words, you cannot get out of a thing more 
than you put in it, and the expense in this case is prohibitive. 

The subject matter of our theme therefore will be confined to the latest 
and most improved compressed air cars now in actual service in three cities of 
the United States, which are started, kept running and stopped by compressed 
air. When it is considered that one of the earliest applications of air in rail- 
road service was its use for air brakes as a 'stopper of trains, it is passing strange 
.that its use as a starter and stopper of trains did not earlier occur to mechanical 
minds. 

Space precludes any general review of the past history of air, except 
to state that it was one of the earliest known of what may be termed the second- 
ary forces or powers. Authentic records of the application of air are found 
among the writings of the Alexandrians, 300 years before Christ, and, later, 
water was used in connection with steam but not much progress was made with 
either of these until the present century, during which such advances have been 
made in the manufacture of iron and steel, which have been used in the con- 
struction of engines, boilers, tubing, etc., as to make the use of steam the most 
important factor in modern life. 

Although the application of compressed air to the propulsion of vehicles 
is of comparatively recent date, the fact that it is used in practically the same 
way as steam gives to it the benefit of all that has been done in the way of the 
perfection of the steam engine. In fact, there are many instances where steam 
boilers have been charged with compressed air and engines operated therefrom, 
and, in one instance, a locomotive was charged with compressed air and run 
about the railroad yards and used for switching, etc. For such purposes, how- 
ever, specially designed machines are better. 

Limited space precludes any but the most general review of this impor- 
tant subject, and certainly nothing is more important to street railroads than the 
question of a power which can be economically applied to all conditions of 



of the 



*TW Vnrl* ^/FtJ^p.S;.o^- pool^^Pfeeident of the Compressed Air Co., at the annual meeting 
New York State Railway Association, held at Buffalo, N. Y., Sept. 18 and 19, 1900. 



r5?qr*-»^f-:v^ 



USE. 483 

jrvice, and which is of so simple a character as to make its operation and 
iiaintenance equally economical. Recently, however, it has been given serious 
consideration and all the claims made for it have been fulfilled. It has proven 
itself reliable, unchanging, and where it has once performed a service it has 
always, under the same conditions, continued to perform that service. Unlike 
steam, compressed air does not have to be used as it is generated. It can be 
stored up and is ready for use when needed. Compressed to any required de- 
gree, it will always return to its normal atmospheric density. 

Briefly described, the construction and operation of an air car are as 
follows, viz. : 

The most approved form of motor now in use in this country, and of which 
a number have just been constructed for the Metropolitan Street Railway Com- 
pany, of New York, for their crosstown lines, consists of two small reciprocating 
engines underneath the car body, each connected directly to one pair of the car 
wheels according to the most approved form of locomotive engineering practice. 
The pair of wheels so driven are connected by parallel connecting rods to the 
other pair of wheels, thus making all the wheels under the car drivers. The air, 
before passing into the cylinders of the engine, passes through a reheating tank 
of water heated to an initial temperature of 300 degrees. The reheating of the 
air before use returns to it all, or a very great portion of, the heat units which 
were taken from it during compression. To illustrate this, a test was made of a 
motor in Rome, N. Y. This motor, which carried thirty-five cubic feet of stor- 
age, was run with cold air, until all the air was exhausted, and covered only 
eight miles. Afterward the same motor was run, using the reheating apparatus, 
and fifteen miles were covered. The heating of the water in the tank is done by 
attaching a steam connection directly from the boilers which furnish steam to 
the compressors, to the reheating tank on the motor and passing the live steam 
into the water. 

In order that the minimum amount of difficulty might be experienced by 
the average motorman, a controller was devised which, in appearance and opera- 
tion, is very like an electric controller. An air brake is one of the features of 
these motors, and an ingenious contrivance in the way of a starter is also con- 
trolled by the brake handle. The valve motion is exceedingly simple, and gives 
a range of cut-off of from i-ioth to 5-8th of a stroke. There is no appreciable 
exhaust and the operation of the motors is practically noiseless. The air brake 
used on these motors is operated from air stored on the car, and is absolutely 
noiseless, both in its application and release. Being operated by the same han- 
dle which starts the car, there is no danger of the motorman leaving his brake 
on and trying to start the car at the same time. 

Cars of this type are in their sixteenth month of operation on the North 
Clark Street Cable line in Chicago, doing the night or owl service on that line, 
and sometimes hauling two trail cars. During the severe winter weather and 
snow storms which prevailed in that city last winter, the compressed air cars 
were the only ones to perform their regular schedule. Compressed air cars 
have been in use in France for several years, and also in Switzerland, and in 
some places in those countries are used to haul two and three trail cars, but 



484 USE. 

the American motors are pronounced by both our own engineers, and engineers 
from other countries, to be far superior to those of European manufacture. 

The storage tubes under the car are of mild steel, capable of withstand- 
ing a pressure of 5,000 pounds to the square inch. Bottles of this character are 
used, both in the power house and on the car; the initial pressure in the power 
house being about 2,500 pounds and on the cars about 2,000 pounds, which pres- 
sure on the cars is, by means of a reducing valve, reduced to about 15 pounds 
to the square inch before going through the reheating tank and thence passing 
into the cylinders. It will be seen, therefore, that there is an ample factor of 
safety allowed by the storage tubes, and, while all precautions which can be, are 
provided, and it is apparent that the further the cars travel the greater the 
factor of safety becomes. The storage on the car is underneath the seats, or the 
car floor, and the cars, in appearance, resemble the standard Broadway, New 
York, cars, none of the storage or machinery being in sight, and no paying 
space is taken up by either. 

We now come to the power house. Air compressors, driven by an eco- 
nomical stationary steam engine, or by water or other power, compress the air 
from atmospheric to 2,500 pounds pressure to the square inch, and as the air is 
compressed it is stored in a battery of steel bottles of the character of those 
above mentioned. During compression, however, great heat is developed and a 
system of water jacketing is used which reduces the temperature of the air to 
that of the surrounding atmosphere. By means of a special separator, all the 
moisture contained in the air is separated from the air as it passes from the com- 
pressor to the storage, thus securing perfectly dry air. It is well known that ex- 
panding gas or air develops an exceedingly low temperature, but the use of the 
separator, removing all water from the air before storage, obviates freezing upon 
expansion, and the passing of the air through the hot water before use in the 
working cylinders restores to the air the heat units which were taken from it 
during compression and also furnishes enough moisture in the form of steam 
to assist in lubricating the cylinders. The exhaust from the engine cylinders 
never falls below 70 degrees. 

In order to recharge the storage on the car it is only necessary to connect 
the storage in the power house with that on the car and equalize the pressure 
between the two. This is usually done at the end of a run, and while the car is 
waiting and takes about two minutes. In Chicago, however, this is done on the 
street and while the car is en route, and has never caused any delay or stoppage 
of the service, even though done while the air cars were running between cable 
trains, 

^ During the last four years experimental and actual demonstration of air 
cars in service have reasonably determined the following facts, viz.: 

That the cars operated in Chicago during a period of six months con- 
sumed an average of 400 cubic feet of free air per car mile, and that the cost of 
maintenance of these motors is much less than that of the ordinary steam engine, 
as there is no boiler to be cared for. 

We have been furnished figures by the most responsible buiMers of air 
compressors in this country, estimating on a volume of 6,800 cubic feet of free 
air per minute, which should be sufficient to operate 100 cars, which show that 



USE. 485 

2 8-10 cents will compress 1,000 cubic feet of free air to 2,000 pounds pressure. 
This estimate is approximate for local conditions, and coal is figured at $2.90 
per ton for a twenty-four hours service, taking two pounds per hour for indi- 
cated horse-power. This includes attendance of engineers, helpers, firemen and 
laborers, and also for oil and waste, and allows for 10 per cent, per annum for 
depreciation. 

The cost of equipping with air cars varies according to local conditions, 
but in the present state of the art is approximately the same as the overhead 
trolley. It is believed that the cost of operation and maintenance through a term 
of years will prove to be very much less, and that increased facilities of manu- 
facture will greatly lessen the first cost. 

It is believed that compressed air cars have a place in every large system 
already installed, whether cable or electricity, either for performing night service 
where it is not advisable or economical to run a large plant for the operation of 
a small number of cars, or where feeders or crosstown lines are necessary and 
the installation of the overhead or underground trolley would not be permitted. 

In brief, the advantages of compressed air for the operation of street 
railways may be summed up as follows, viz. : 

First — A system of independent motors, which, after receiving their 
charges, do not rely upon the power plant and which will always finish their run 
should anything happen to the power plant; which also do not need any special 
outdoor construction, either underground or overhead, with the attendant cost 
of maintenance. 

Second — Slow moving machinery, both in the power house and on the 
car, which is easily maintained. 

Third — Opportunity for charging cars, and storage in power house, dur- 
ing light hours, for use during rush hours. 

Fourth — Spring supported motors and load, doing away with excessive 
jarring and pounding on track, and thus greatly prolonging the life of the road- 
bed, the life of the motors, and contributing to the easy riding of the cars. 

Fifth — Low first cost of plant; low cost of maintenance, and opportunity 
for making repairs and adjustments without stopping the operation of the cars. 

Sixth — Freedom from liability in transit from snow, ice or sleet. 



HARDIE CARS RUNNING IN CHICAGO. 

The compressed air motor cars on the North Clark street cable road in 
Chicago are making a good record for themselves, and much can be said of their 
reliability. 

The first car made its initial trip May 30th ; soon after the second car was 
put on, and a third car is held in reserve to provide for any emergency or 
accident. 

No trouble has originated from lack of efficiency on the part of the inex- 
perienced motormen. They were instructed originally by Robert Hardie and 
have been able to handle the cars perfectly ever since. 



486 USE. 

The cars still continue to make the first trip from air that was left over 
from the previous night service, and, on one occasion, one of the cars made an 
excursion trip in daylight for the benefit of those who were invited to be present, 
and still made its regular trip at night with what air was left from the preceding 
night. 

From May 30, 1899, to June 20, 1899, inclusive, car No. 107 ran alone. On 
June 2 1 St car 102 was put in service, and since then two cars have been running 
regularly and doing the complete "Owl Car" service. 

In order to show the actual service performed by these cars a brief table is 
given: Car Car Car 

No. 107. No. 105. No. 102. T'ls. 

No. of miles covered 1,232 189 616 2,037 

No. of trips without trailer 148 21 84 253 

No. of trips with one trailer 26 6 4 36 

No. of trips with two trailers 2 . . . . 2 

-Total No. of trips, each car 176 27 88 291 

No. of passengers carried paid fares 24,294 

No. of hours car service from June 21st to July 17th 

inclusive, for two cars 142 

No. of hours compressor ran from June 21st to July 
17th, inclusive 93h. 43m. 



THE HARDIE NEW VALVE GEAR. 

Mr. Robert Hardie has invented a new valve gear for his compressed air 
motors, and is having it put on a sixty-foot car now being built at Rome, N. Y., 
and later it will be applied to the street cars equipped with the Hardie air 
motors. The object sought in the invention was to obtain an arrangement 
whereby a cut-off valve could be worked in conjunction with the main valve by 
one lever. The new gear gives a cut-off (including clearance) at any desired 
point between i-io to nearly J/2 stroke. In the position of earliest cut-off there 
is also the greatest amount of lead, as has been shown by a working model of 
the gear. 

A regular Stephenson link with a fixed cut-off (from i-io to 1-5),. worked 
by separate eccentrics, was formerly used on the Hardie cars. While a late cut-off 
results in a greater consumption of air than an early cut-off, the advantage comes 
in being able to adopt smaller cylinders. We defer illustrating the new gear until 
the foreign patents have been granted. 

The figures in the accompanying table were calculated from valve and 
piston movements of the model. The indicator cards for each of the three 
positions of the reverse lever, as here shown, were drawn from calculations based 
on the figures obtained from the actual movements of the pistons and valves of 
the model. The expansion curve in each card is between the adiabatic and 
isothermal. 

In the following table, are given the openings for every 30 degrees of the 
main and cut-off valves for three positions of the link, with 3-16 inch for both 
outside and inside lap of main valve, and 11-16 inch negative lap of cut-off valve. 



PTTn^sp 



USE. 



487 



These figures are for cylinders 6^ x 12 inches, and admission port, J^ x ^ inches. 
The inside and outside lap being equal, the main valve compression and cut-ofif 

TABLE 46 — RESULTS OF DISTRIBUTION OBTAINED BY THE HARDIE VALVE GEAR. 





First Position. 
Main valve (full) travel, 2 in. ; cutoff valve travel, 2 in. 


Crank angle, deg. 


Cut-ofE valve opening, 
inches. 


Main valve opening, 
inches. 


Piston travel, 
inches. 




Front. 


Back. 


Front. 


Back. 


Front. 


Back. 





if 


-H 


'A 


-ft 
-ih 

-it 


% 

w 


3V 

n 

A 

-A 


.0 

.94 

3.39 

6.53 

9.39 

11.33 

12.00 


.0 


30 

60 

90 


.67 
2.62 
5.48 


120 

150 


8.63 
11.06 


180 


12.00 







Main cut-off and compression crank angle, 117°. 

Lead angle of cranks : front, 18° ; back, 18°. 

Point of cut-off not including clearance ^— i^ of stroke. 

Point of cut-off including clearance — -- of stroke. 

Greatest port opening, -i^ in. 

Relative travel of main and cut-off valves, i^ in. 



TABLE 47— RESULTS OF DISTRIBUTION OBTAINED BY THE HARDIE VALVE GEAR. 





Second Position. 
Main valve travel, \\ in,; cut-oflf valve travel, i\\ in. 


Crank angle, deg. 


Cut off valve opening, 
inches. 


Main valve opening, 
inches. 


Piston travel, 
inches. 




Front. 


Back. 


Front. 


Back. 


Front. 


Back. 





1 

-ii 
— U 
-A 

6 
Iff 


ItV 

—A 

-^ 

5 
— 77 


3^ 


tV 
it 


.0 

.94 

3.39 

6.53 

9.39 

11.33 

13.00 


.0 


30 


.67 


60 


2.62 


90 


5.48 


120 


8.62 


150 


11.06 


180 


12.00 







488 



USE. 



Main cut-off and compression crank angle, 138 

Lead angle of crank : front, 13° ; back, 13''. 

Point of cut-off not including clearance 

Point of cut-off including clearance j^ 

Greatest port opening, ^ in. 

Relative travel of main and cut-off valves, 2r| in. 



irk o^ st^°^^- 
of stroke. 



TABLE 48 — RESULTS OF DISTRIBUTION OBTAINED BY THE HARDIE VALVE GEAR. 





Third Position. 
Main valve travel, 1 in. ; cut-off valve travel. IJ^ inch. 


Crank angle, deg. 


Cut-off valve opening, 
inches. 


Main valve opening, 
inches. 


Piston travel, 
inches. 




Front. 


Back. 


Front. 


Back. 


Front. 


Back. 





li 

-A 



-iV 

-A 

A 


Vs 

H 
A 

-tV 

—A 
-U 


A 
iV 
A 
A 
-A 


.0 

.34 

3.39 

6.53 

9.39 

11.33 

12.00 


.0 


30 


.67 


60 


2.62 


90 


5 48 


120 


8.62 


150 


11.06 


180 


12.00 







Main cut-off and compression crank angle, 148**. 
Lead angle of crank : front, 12° ; back, 12**. 
Point of cut-off not including clearance ~ — of stroke. 
Point of cut-off including clearance -^ of stroke. 

9-54 

Greatest port opening, xV in. 

Relative travel of main and cut-off valves, 3^ in. 



take place at the same point. The greatest port openings are taken at the point 
where cut-off and main valve openings are equal, the cut-off closing while the 
main valve is opening. There is always ample exhaust opening. The readings in 
the table were taken (for convenience) at equal crank angles, but the valves 
would be set to cut-off at equal piston movements from each end of the cylinder 
The clearance in the cylinder is 4 per cent. The cut-off, including clearance, a? 
noted under each card means 

Piston travel at cut-off + clearance 



Stroke of piston + clearance. 



USE. 489 

THE HARDIE AIR-MOTOR CAR. 

The first of the two Hardie air-motor street cars to be tried by the Third 
Lvenue Railroad Co., arrived in this city July 22, 1896. It was shipped on a plat- 
form freight car on the New York Central Railroad from the works of the Amer- 
ican Air Power Company at Rome, N. Y., where it was manufactured. The new 
car was taken from the freight car at 129th street and Hudson River, whence it 
was propelled by its own power about 1,000 feet to the station of the 42d street, 
Manhattanville and St. Nicholas Avenue Railroad, at 129th street, between 
Twelfth avenue and the Boulevard. 

Its air tank was charged, just before the car was taken from the works, 
with compressed air to a pressure of 2,000 pounds to the square inch, and in the 
three days that elapsed from that time the loss of pressure was only twenty 
pounds, which is regarded as small. 

The weight of the car complete is 18,000 pounds. Of this, 6,000 pounds 
may be charged to the car body, 500 pounds to hot water for heating the air, 500 
pounds for the compressed air itself, and the rest to the truck and motive equip- 
ment and air cylinders. The controller, or throttle and reverse lever as Mr. 
Hardie prefers to call it, is situated on the front platform, and is strongly sug- 
gestive of the ordinary street car controller. A crank handle operates the throttle 
valve which admits air to the engine cylinders and controls the motions of the 
car. The reversing lever merely throws the Stephenson link, or regulates the 
grade of cut-off. A third lever controls the air-brake, and also by swinging over 
to another position can admit air to the ends of the cylinders for starting, after 
the cut-off valves have closed, and also make the air pressure momentarily much 
higher to start off rapidly. This Mr. Hardie calls the accellerator. The brake 
is released by equalizing the pressure on either side of the piston by a specially 
designed valve. This action takes place almost instantly. A fourth handle takes 
the place of the hood switch on the electric car and cuts off the air altogether. 
The motorman takes all these four handles with him and covers up the top of the 
controller with a brass cap, thus preventing intermeddling by passengers, and also 
preventing the soiling of clothing by oil or grease. 

The car is 28 feet long, its body being 20 feet long, and the remaining 8 feet 
being occupied by the two platforms. It has a seating capacity for 28 passengers, 
and when its compressed air and hot water tanks are charged, it can run 16 miles 
without recharging, and is capable of attaining a speed of 15 miles an hour. 

The motorman controls the machinery with a little lever only 6 inches long, 
while the rate of speed is graduated by the use of valves, by which the pressure 
of the motive power on the engine cylinder, usually 150 pounds to the square inch, 
is regulated. 

A movement of the lever one inch to the right lets off the brake and starts 
the car, while a movement one inch to the left puts on the brake and stops the car, 
and a further movement to the left starts the car backward. These movements 
can be made so easily, and the car started, stopped or backed so quickly, that it is 
contended danger of accident is reduced to a minimum. 

The wheels and the hot water and compressed air tanks, which are under- 
neath the car, are concealed by a drop, or curtain, composed of slats of wood. 



490 



USE. 



THE HARDIE AIR MOTOR. 

Mr. Frank Richards, in a letter to the New York "Sun," speaking of the 
cars running on 125th street, New York, says: "Each car is independent of 
every other, and independent of the roadbed. The disablement of one car affects 
only itself. It is the safest system known. No passenger has ever discovered 
or suggested an objection. The officers of the Third Avenue Railroad Co., upon 
whose lines the cars have run, have entirely failed to discover any objection to 
the system, and state so officially." — Mr. Albert J. Elias, President of the Third 
Avenue R. R. Co., N. Y., in a letter to Mr. E. A. Willard, President of the 
American Air' Power Co., dated March 31st last, writes : 

"Your cars operated by compressed air have been steadily operated on the 
125th street line of the Third Avenue Railroad Co. since the 3d of August last. 




FIG. 164 — ROBT. HARDIE AND HIS MOTOR. 



They have been easily handled, started, stopped and reversed; the last named 
quality being a very desirable feature, reducing the liability to accidents. Of 
course, the advantage of a motor that operates independently of connection with 
any subterranean motive power is apparent. I have not been able accurately and 
definitely to determine the relative cost of this compared with other motors, but 
am quite sure that it is not greater, and am of the impression that it is less than 
animal and probably less than cable traction. The motors are capable of attain- 
ing high speed and overcoming considerable gradients." 

The following from the "Railroad Gazette" shows that the Hardie system 
is attracting attention abroad: 

"Sir A. B. Forwood, a large owneF in the Liverpool, England, tramway 
system, before the city acquired the plant, has been for a considerable time mak- 



USE. 491 

ing an investigation by direction of the Liverpool authorities for the purpose of 
report, of the working of the Hardie Air Motor on 125th street, New York. He 
employed as an expert, Mr. A. Thomson. The report which has been forwarded 
contains detailed description of the motors and plant now in use in New York, 
together with estimates of cost of their working. The report concludes as fol- 
lows: 'Looking at this system from a mechanical point of view, there appears 
to be no doubt of its efficiency. The details connected with the service which 
we examined have been very carefully wrought out and constructed, and the ma- 
chinery appeared to have sustained no wear and tear of any moment after con- 
tinuous service of about eight months. The arrangement of the machinery in the 
car is that of a plain simple engine, the working parts are of good, strong section 
and design, and should last for a long time with a very little upkeep, and we 
have no hesitation in stating that a plant fitted upon this system, with the ar- 
rangements and details carried out properly to begin with, would work as great 
or greater efficiency and more economy than any other system which we are 
acquainted with.' " 



COST OF OPERATING AIR CARS IN NEW YORK CITY. 

It seems especially pertinent at this time to publish a statement of the 
actual operation and operating expenses of the American Air Power Company's 
cars that have performed a regular commercial service on the i2Sth St. line of 
the Third Ave. R. R. in New York City, since the 3d of August, 1896, with a 
success unparalled in the history of mechanical traction. 

The period elapsed covers the extreme ranges of temperature experienced 
in this locality, and fortunately also two snow storms of more than ordinary 
severity, so that the seven months continuous duty on which the following state- 
ment is based will meet the conditions incident to any street railway service. 

The 125th St. line of the Third Ave. R. R., extends across town from the 
North River to the Harlem River, the length of the tracks being 10,854 feet, mak- 
ing the round trip 4.1 1 miles, over which cable cars are operated at intervals of 
2>^ minutes. Air cars were substituted for two of these cable cars, the schedule 
calling for 19 round trips each, or 79.09 miles per car; for a daily service of 
156.18 miles besides 1.14 miles of switching to and from the car house and street 
tracks, making the total distance covered daily, 157.32 miles. Each car runs from 
12.50 to 16.67 niiles on a single charge of air. 

The switching referred to is unavoidable in operating this service owing 
to the arrangement of the car-house in relation to the street tracks, it being some 
distance from the terminal of the road. 

During a portion of the time, only single service was performed, as at 
present, so that the total average mileage per day, from August 3d to March 3d. 
was 125.16 miles, and the total distance covered, 23,030.5 miles; and the total 
number of passengers carried, I37»386. The cars have operated every week-day, 
but are not run Sundays. 

The accompanying profile of the 125th St. line shows that the grades to 
overcome fairly represent average conditions in New York. The grade from 



492 USE. 

Fort Lee Ferry east to the Boulevard being 1.96%, while at the New York Cen- 
tral R. R. tunnel crossing, the maximum grade is T.jJo for a short distance, 
which is just as difficult to start the car upon as a long grade of the same ascent. 

In the following statement of operating expenses, the coal and water items 
include all that has been used at the compressing plant during this period, and 
the labor account includes in addition to the operating employees, a night watch- 
man, record keeper, and also switchman for a portion of the time. It must 
also be borne in mind that the fires are kept under boilers for 24 hours, although 
the compressor only runs 7 hours daily. 

Actual average cost per car mile for entire period — 7 months — 125.16 
miles per day. 

Coal $0.0563 

Water 0103 

Oil and Waste 0013 

Power Plant Labor 1261 

Conductor and Motorman 0608 

Repairs, Car Equipment 0038 



$0.2586 
Average present cost per car mile, while one car service performed — 78.09 
miles per day. 

Coal $0.0675 

Water , 01 13 

Oil and Waste 0017 

Power Plant Labor 0833 

Conductor and Motorman 0608 

Repairs, Car Equipment 0038 



$0.2284 

Average present cost per car mile with two car service — 156.18 miles per 
day. 

Coal $0.0433 

Water 0103 

Oil and Waste 0013 

Power Plant Labor 0833 

Conductor and Motorman 0608 

Repairs 0028 



$0.2018 



If the proportion of labor actually utilized in this service is considered, the 
expense would only amount to $0.1791 per car mile at present. 

Present number of employees, six, besides conductors and motormen. 

The reason for the present cost of operation being lower than the average 
for entire period is that the number of employees has been reduced in addition 
to a less air consumption by the car. The number of employees at present is, 



lli 



USE. 



493 



however, sufficient to operate a fifteen car service, so that the proportion of labor 

charges per car mile is still very high. 

At a recent conference of several engineers, who investigated the cost 
of operating the American Air Power Co.'s system in behalf of a street railway 
now operating a large number of cars at intervals of one minute, it was deter- 
mined after careful examination, and agreed that for the items above enum- 
erated, the cost per car mile would in no event exceed $0,085, and that with a 
large equipment of cars in service, like that performed on 125th St., the cost 
would only be $0.0756 for the same items now costing $0.2018, while operating 
the two car service. This would make the total operating expense of such a road 
about 12 cents per car mile. 

For the benefit of any who may not be familiar with the operating cost 
of so small a number of cars by mechanical power, the following data is fur- 
nished: 

In the recently published report of the operating expenses of 22. electric 
roads in Connecticut for 1896, the West Shore Street Railway Co., West Haven, 
is reported as operating precisely the same mileage, namely 4. 11, with the same 




FIG. 165 — rKCFILE SHOWING GRADE ON I25TH ST., NEW YORK. 



number of cars in service, having, however, only five employees, and the average 
cost of operation per car mile is shown as $0.2991. 

In the published report referred to, the average cost of operation per car 
mile of the 22 roads given, is $0.1444; and in the 20 roads having the items of 
motive power, and line repairs given, the average cost appears as follows : 

Motive Power, Average $0.02816 

Line " " 00270 



$0.03086 



The average consumption of free air per car mile for the seven months 
service of air cars on 125th St., has been 477.7 cubic feet. During the severe 
snow storm of December 16, 1896, the cars performed the schedule service with 
promptness and regularity, carrying 20 per cent, more passengers and using 
22% more power than the day previous. In comparing results with an electric 
road in this vicinity, it appears that with 2)1% less service than the day previous, 
the load on the power-plant was about 80% greater. 

During the last week, the average consumption of free air per car mile 
was only 414 cu. ft., and many of the trips were made on considerably less than 
400 cu. ft. 



494 . USE. 

The actual cost of compressing air to 2,500 pressure per square inch, and 
storing for use in a modern air compressing plant operating with condensing 
engines including coal at $2.75 per ton, water, at $1.00 per thousand cu. ft., oil 
and waste, the removal of ashes, labor, repairs and maintenance of power-plant, 
depreciation, and interest on cost of entire power-plant including buildings, for 
compressing plants of the following capacities, based on the consumption of 2^ 
lbs. of coal per hour, per horse power for 20 hours per day, will not exceed the 
following figures : 

Cost per i.cco cu. ft. of free air compressed to 2.500 lbs. pressure per 



sq. m. 



Station Cr.pf.city. 

500 CU. ft. per minute $0.0675 

0571 



1,000 
2,000 
3,000 
4,000 

5,000 
6.0C0 
7.000 
8.000 
9.000 
10,000 



0469 
0419 
0394 
0375 
0359 
0342 
0326 
0312 
0300 



Responsible parties will guarantee that the cost will be less than stated, 
and the writer believes that the cost in highest grade plants can be reduced fullv 
25%. 

Assuming the average consumption of air per car mile can be kept as low 
as at the present time, the average cost of motive power per car mile on the 
above basis, would range from $0.0124 to $0,027; or an average of $0.0197; and 
even if 477.7 cu. ft. the same as averaged for the past seven months in regular 
service, the cost per motive power per car mile, will range from $0,014 to $0,032. 
or an average of $0,023. Placing these figures against the cost of motive power 
as averaged in the Connecticut electric roads for 1896, the results seem to show 
considerabl}' in favor of compressed air as a motive power. 

This cost of motive power, based on 20 hours service, does not represent 
the lowest cost that is available for the different capacities in the best practice 
for this reason, that in a compressed air plant having station storage reservoirs 
for accumulating the air, the engines can be worked at a uniform load at the 
most economical point of cut-off, for say 16 hours after which the engines may 
be shut down and the power-plant charges stopped. 

At the 125th St. compressing plant, the engine is operated only about 7 
hours daily, while the cars perform a 12 hour service from a 7 hour station duty. 

The process of operating the compressed air system on 125th St., is as 
follows : 

The air is first compressed by a steam actuated air compressor, which is 
compounded in three stages from which the air passes through a cooler and 
dryer and is accumulated in a nest of Mannesmann steel flasks which are all 
connected in multiple by a series of headers or manifolds, in which stop valves 



USE. 495 

are placed for controlling and confining the air to be stored at a maximum pres- 
sure of 2,500 lbs. per square inch. A pipe leads from this air storage to the car 
house charging stand placed alongside the track, which consists of a copper 
pipe in three sections, having a controlling valve and flexible joints and a charg- 
ing nozzle at the end. All the joints and the nozzle are self-packing, so that no 
leakage has occurred in the seven months' service. After the car has been con- 
nected by inserting the nozzle in a pipe at the side of the car track, the charging 
valve is opened and contents of the station storage flasks admitted until the de- 
sired pressure — 2,000 lbs. per square inch — is registered by the car storage gauge. 
When the charging valve is closed, and a small bleeding valve in the charging 
pipe opened, permitting the high pressure air in the short length of pipe to es- 
cape, at the same time a check valve in the car piping closes automatically pre- 
venting any escape of air, after which the nozzle is removed and the car ready 
for another 17 miles' service. The entire time occupied, including connecting 
and disconnecting in actual daily service, takes less than 2 minutes, and has been 
done in less than i minute in numerous trials. 

At the same time the car is being charged with air, another nozzle is intro- 
duced to the heater connection, and live steam from the boilers is admitted, until 
the temperature registered is about 300 degrees Fahrenheit. 

The air storage reservoirs on these cars have a capacity of 51 cu. ft., suf- 
ficient to run the car 18 to 20 miles continuously, or from 14 to 17 miles, making 
the stops incident to ordinary street railway service. A larger capacity could 
readily be installed on the car, giving it ample power to run 20 miles with a 
reserve. The reservoirs consists of seamless steel flasks capable of standing a 
pressure of double that used without reaching the elastic limit of the metal and 
with no possibility of leakage. They are 9 in. in diameter and of varying 
lengths adapted to their location under the seats and the car floor. Between the 
flasks and the motor is placed a small tank containing 6 cu. ft. of water which is 
heated as before described. The tank is jacketed with non-conducting material 
preventing external radiation. This provides not only against loss of heat, but 
also against any perceptible rise in the surrounding atmosphere, so that no dis- 
comfort can arise from it. 

Numerous trials have proved that the application of heat as employed in 
this system enables the cars to. run nearly double the distance that cold air will 
carry them. 

In operation, the compressed air, after passing through a reducing valve 
and being lowered to 150 pounds to the square inch (the working pressure), cir- 
culates freely through the hot water, and a mixture of heated air and vaporized 
water passes to the motors, working expansively, the terminal pressure being 
so low as to cause no sound in exhausting the air. 

The motor mechanism consists of two simple, link-motion, reciprocating 
engines having cylinders seven inches in diameter and fourteen inch stroke, with 
valves cutting off at from i-io to 1-6, and applying the power by connecting and 
parallel rods direct to the crank pins of the drive wheels which are four in num- 
ber, twenty-six inches in diameter, running on a wheel base of seven and one- 
half feet. Upon this four-wheeled truck rests the entire weight of the car and 
mechanism, evenly distributed upon elliptic springs, enabling the car to pass 
much more smoothly over bad track and crossings, than an electric car (on 



496 



USE. 



which the motors are a dead weight upon the axles) besides being a great saving 
in wiear on the rails at the joints, and on the rolling stock. 

The mechanical features of the motors are substantially identical with 
those of a steam locomotive, minus fire box and boiler, which in point of per- 
fection in mechanism as a moving power, is too well known to need any com- 
ments. 

The manipulation of the car is simplicity itself, requiring no special skill 
or training to handle with perfect facility, and capable of being moved in either 
direction as little as two inches. 

It is perfectly noiseless, odorless, and entirely free from any other offensive 
feature, sending neither smoke nor steam into the air. It responds to the start- 




FIG. l66 — THE HARDIE MOTOR CAR, 1897. 



ing and stopping devices with remarkable promptness, operating without any 
jerks or jars. 

This feature of easy and perfect control seems to me to be the most vital 
point in relation to the public; as in other respects (freedom from the element 
of danger to the public as a manifestation of power), its non-hazard superiority 
is easily demonstrated. The ease and infallibility of control excels that of any 
other system known to the writer for street railways, and can never fail so long 
as the car has ability to move. 

The car is fitted with specially designed air-brakes of sufficient power, with 
the high-pressure air always at command, to set the wheels instantly if desired, 
by a single wrist movement of the motorman. Upon releasing the brakes there 
is an entire absence of noise of any kind from either the mechanism or escaping 
air, which is so noticeable and annoying with air-brakes generally. 



USE. 497 

The same lever that releases the brakes, operates, by a slight advancing 
movement on, the quadrant to open a by-pass admission of the compressed air, 
directly into the cylinders of the motors, enabling them to start easily and posi- 
tively, whatever the position of the cut-off valves may be, and preventing any 
possibility of being stopped on "dead centres," after which the throttle is opened. 
This ability to start so promptly and surely under all conditions, is a feature 
possessed by no other reciprocating motor, and the inability to overcome this 
difficulty has been one of the principal causes of failure in kindred types of 
motors heretofore exploited. The application of the principle of a by-pass ad- 
mission of air into the cylinder, seems to be confined exclusively to the motors 
of the General Compressed Air Company, and is of the greatest importance, 
materially affecting the economic operation of the motors, aside from assuring 
their infallibility in starting. 

The entire system embodying the mechanism and method of developing 
and "applying the power, for the purposes under consideration, consists of sim- 
ple, practical devices, operating on the most approved principles, from which 
all offensive and uneconomic features have been eliminated and better fulfilling 
the requirements of an ideal means of street car propulsion than any other within 
the writer's knowledge. edward e. pettee. 

March 15, 1897. 



FACTS IN REGARD TO AIR POWER AND AUTO-TRUCK COMPANIES. 

During the past two weeks a great deal of publicity has been given to the 
various companies which have been organized by persons directly interested in 
Hoadley-Knight Compressed Air appliances. Messrs. Hoadley-Knight have 
patented Motors for operating Street Cars, Carriages and Trucks. 

In the early part of last year The American Air Power Company was 

I formed by the combination of the Hoadley-Knight and Hardie Companies. Capi- 

Ital $7,000,000. Its president is Mr. A. A. McLeod, formerly president of the 

-Reading Railway, and its directors are William L. Elkins, Thomas Dolan, 

Thomas Ryan, Joseph H. Hoadley and A. A. McLeod. Its relations with the 

Metropolitan Street Railway Company are very close. 

Arrangements have been made by The American Air Power Co., with the 
Metropolitan Street Railway Company allowing the equipment of the 28th and 
29th Sts. crosstown lines in New York with cars having improved air motors. 
The work of installing the plant at 24th St. and 13th Ave. for that purpose is now 
progressing rapidly. The Air Compressor and twenty cars are nearly completed. 

Messrs. Hoadley-Knight are also interested in what is known as the Auto- 
Truck. Imbued with the idea that this truck answers all the requirements of 
automobile traction, another company has been formed for the purpose of 
developing the Auto-Truck. The Hoadley-Knight Truck was fully described in 
the December, 1898, number of Compressed Air, showing a truck as constructed, 
and used in the works of the Am. Wheelock Engine Co., Worcester, Mass. 

The company known as the New York Auto-Truck Company was organ- 
ized under the laws of New Jersey and capitalized at $10,000,000. Its incorpora- 



498 USE. 

tors are Richard Croker, Nathan Straus, Lewis Nixon, Robert I. McKinstry, 
Senator Arthur P. Gorman, Joseph H. Hoadley. 

Still another company has been recently organized under the auspices of 
Messrs. Joseph H. Hoadley, William E. Knight, Harry E. Knight, Robert I. Mc- 
Kinstry and Edwin F. Glenn, known as the International Air Power Co., with 
capital stock $7,000,000. The purpose of this company is to operate in foreign 
countries under patents similar to those assigned to The American Air Power 
Company and the New York Auto-Truck Company, the Hoadley-Knight foreign 
patents on pneumatic traction not having been assigned to The American Air 
Power Co. The daily papers of New York and elsewhere have given wide cir- 
culation to the plans of the movers in these compressed air enterprises, and the 
impetus thus created has provoked numberless inquiries as to the feasibility of 
the published claims. 

All that can be said at this writing is that the avidity of the newspapers is 
responsible for many of the assertions that lack the stability necessary to useful 
results; at the same time, the publicity has produced a healthy consideration of 
compressed air. 



COMPRESSED AIR TRUCK. 



Compressed air is the most compact, the lightest and the cheapest stored 
power outside of original fuels, and lends itself perhaps more readily to the 
horseless-vehicle than it has to the man}'- other applications that has been made 
of it. Thus there might be some question as to compressed air cars having very 
decided advantages over the trolley or the cable car, they all run on a definite 
route and on a definite schedule, but for miscellaneous routes and miscellaneous 
traffic, freight or passenger, compressed air has as its only competitor the electric 
storage battery, over which it claims many advantages. 

Air compressed to 2,500 and 3.000 per square inch can be stored in a rea- 
sonable space on a truck, or other vehicle, and will carry the same 20 miles. The 
air is handled in exactly the same manner to that used on the compressed air 
cars, that is, it is let out from the reservoirs by an automatic reducing valve to 
the motors at a pressure of about 200 lbs. per square inch, its introduction to the 
motor being controlled by the ordinary throttle valve. The motor that is used 
for this purpose is of the ordinary Hoadley-Knight type, that is to say, it is an 
iron-clad motor, having all of its working parts in a closed iron basin partly filled 
with oil, so that no attention for lubrication is required. A simple wedge move- 
ment enables its operator to reverse the motor or control the point of cut-off. 
This is done by the lower hand wheel, shown in the cut. The upper hand wheel 
is used for steering purposes, it being connected to a segmented gear, attached 
to a single steering wheel. The throttle is controlled by a lever which is opened 
by the operator pressing his knee against it, and is closed by the action of a 
spring. The motor drives both the rear wheels through a compensation bevel 
gear arrangement, thus allowing it to turn in any direction. The truck when 
working under ordinary conditions consumes about 75 cu. ft. of air per mile. 
This would involve a cost per mile for power of less than one cent. 

The compressed air truck in our illustration shows very forcibly the sub- 



USE. 



499 



stantial progress being made in the automobile field by the compressed air experts. 
Here is a truck which will handle ten tons of freight, and which occupies a space 
of 4 X 15 feet. It is guided and controlled with such ease that it is safe in the 
hands of the most ignorant operator. It is claimed that it will run about half a 
day on one charge of air, and will operate with a power cost not exceeding one 
cent a mile. The absence of all combustion of any kind insures the popularity of 
this form of stored power, and its great economy as compared with storage bat- 
teries places it in the lead of the possible powers for automobile work. For the 
race that must start in the near future for commercial supremacy in the auto- 
mobile field, there are preparing in the mechanical world many radically different 




FIG. 167 — COMPRESSED AIR TRUCK. 



"orms of motor vehicles. The race cannot be said to be started until actual 
;ompetitive manufacturing has begun. Doubtless there will l)e found special 
ields available for several of the more successful types. There is the long dis- 
ance work for vehicles traveling out many miles from the center, which of 
lecessity cannot well be supplied with power from a central station. There is 
he light vehicle competing with the single horse rig for which almost any form 
)f motive power is suitable, but which can, perhaps, after all be best operated by 
he horse. There is, again, the omnibus field which, running as it does over 
iniited and definite routes, can evidently be operated by a secondary charge from 
ome central source of power, such as stored steam, compressed air or storage 
catteries. There is, further, the field of heavy trucking which amounts to many 
imes more than all the rest of the work done by horses put together. This 
rucking being generally confined lo the city streets, and to limited distances, and 



500 



USE. 



often to definite ^-oiites, is again a field open for secondary stored powers operat- 
ing in conjunction with central stations, and it is an attempt to occupy this field 
that gave birth to the truck shown in our illustration. The attempt will be made 
to handle greater loads with more expedition and with the occupying of less 
space in the street than can be done with horses, and in these features the chief 
sources of economy are expected to be derived. Apart from the saving brought 
about by the substitution of mechanical power for animal power, the item of 
wages will be materially reduced. It is evident that with heavy loads moving at 
greater speeds the operator's time will be just so much economized. 

The truck, as shown, is in daily use at the works of the American Wheelock 
Engine Co., Worcester, Mass., and fills a long-felt want in moving large castings 
and other bulky work from place to place without the need of cranes or hand 
trucks. 

The air truck has been developed by the Pneumatic Carriage Co., and is 
being manufactured by the American Wheelock Engine Co., Worcester, Mass. 



ANNUAL MEETING OF THE AMERICAN AIR POWER COMPANY. 

The annual meeting of the stockholders of the American Air Power Com- 
pany, which had twice been adjourned, was held recently, when A. A. McLeod, 
president of the company, tendered his resignation, he to continue, however, as a 
director. He will be succeeded by H. H. Vreeland, of the Metropolitan Street 
Railway Company, which is largely interested in the American Air Power Com- 
pany. Directors were elected as follows : William L. Elkins, Thomas Dolan, T. 
H. Vreeland, J. H. Hoadley, A. A. McLeod. With the exception of Mr. Vreeland, 
who succeeded Gen. G. E. P. Howard, resigned, these had served on the previous 
board. 

Following is a report read by the retiring president, Mr. McLeod. 

"Mention was made in the last annual report of the contract your com- 
pany made with the Metropolitan Street Railway Company for the establishment 
of a plant and the equipment of twenty cars to be put on the Twenty-eighth and 
Twenty-ninth street line. 

"This line was put into operation in July last, and the cars have been in 
successful operation since that time. In August last, under the terms of the con- 
tract, the line was turned over to the Metropolitan Street Railway Company for 
the purpose of making an operating test, which is now being made. 

"The cars are giving excellent service, the traffic on the line has increased 
very largely, and the result of the operation thus far is very gratifying, and may 
be considered a commercial success. 

"It may be said that when the cars were first put into practical operation 
some few mechanical defects were discovered which could not be foreseen, as is 
likely to be the case with every new device, but the short experience already had 
has enabled your engineers to make such improvments as were necessary, and as 
a result the latest improved car which has been put on the line is giving great 
satisfaction. 



p^ 



USE. 501 



"I am of the opinion that the method of propelling street cars by compressed 
air, the patents for which are exclusively owned by your company, is on the eve 
of such success as will prove very gratifying and valuable to your shareholders, 
and enables me to turn over to my successor in such a way as to secure for your 
shareholders the greatest possible advantage. 

"As the Metropolitan Street Railway Company is the largest individual 
holder of your capital stock, and as it has a very large street car mileage in this 
city which is now operated by horse-power, naturally the first work of importance 
for your company will be the equipment of these lines, and as Mr. H. H. Vreeland, 
the president of that company, has kindly consented to take the presidency of 
your company, I believe it will be greatly to the interest of your shareholders to 
elect him president. 

"I, therefore, decline a re-election, and while I regret that I feel it incum- 
bent upon me to do so, owing to the pressure of other business, the affairs of your 
company are so well established and will be conducted in the future by so able and 
experienced a man as Mr. Vreeland, that I am sure your interests will not only 
not suffer, but be greatly enhanced. As a member of the board I shall continue 
my interest in the company." 

Mr. Vreeland says that his election to the presidency of the American Air 
Power Company, which has been operating the cross-town cars on Twenty-eighth 
and Twenty-ninth streets by compressed air, would not affect the policy of the 
company materially. The American Air Power Company, he said, has always 
been in close touch with the Metropolitan, being practically under the control of 
that company since its formation. The present equipment, used only on the 
Twenty-eighth and Twenty-ninth street lines, will be increased as soon as possi- 
ble, and air motor cars will be placed on Thirty-fourth street. 

The problem of the downtown crosstown lines, he said, has not been taken 
up as yet. The success of the air power cars was assured, declared Mr. Vreeland, 
and the defects which at first appeared in the mechanical equipment had been 
remedied. 



AN AIR WAGON. 



The illustration (Fig. 168) on page 502 is an air wagon constructed by 
Chas. D. P. Gibson, and is the property of the Air Vehicle Company, of New 
York, The engine is of the usual 2-cylinder type, and weighs 36 pounds, and 
has several special features in its construction. It is adapted for the use of air 
or steam, as may be required. With the use of air it has a storage capacity of 
six cubic feet, which could be increased without material addition to the total 
weight of the wagon, which is with the present capacity 670 pounds. 

With air as a power appliance for reheating the air is used. The air is 
stored at a pressure of 2,500 pounds per square inch, and reduced to an initial 
cylinder pressure of 150 pounds by an ingenious arrangement of reducing valves, 
which are under the control of the operator and allowing the working pressure to 
be regulated as required. 

On a recent trial on a bad road this wagon was operated with a consump- 
tion of 60 cubic feet of free air per mile. The condition of the road was much 



502 



USE. 



below the average, and the trial was not one which would give the most" eco- 
nomical results in the use of the power, yet under these conditions it would be seen 
that the storage has capacity to run the wagon 20 or 30 miles. And as it is 
estimated that air can be compressed for less than 4 cents per 1,000 cubic feet, it 
is believed that it will prove a desirable and economical power for propelling 
omnibusses and delivery wagons which have a definitely determined route to 
travel. Its freedom from odor or visable final exhaust makes it the ideal power to 




FIG. 168 — THIS AUTOMOBILE IS OPERATED BY COMPRESSED AIR, AND BUILT BY THE 
AMERICAN VEHICLE CO., NEW YORK. 



use. The engines of this wagon operate equally well with steam, and buyers are 
to be supplied with steam wagons or air wagons as they may desire. 

With steam the power is supplied by a small steam boiler, the fuel is gaso- 
line, the supply of which is automatically controlled by the boiler pressure, and 
the water feed operated by the engine and under the control of the person operat- 
ing the wagon. 

The steam wagon has no radical departures in use of steam in engine or 
boiler, but special care and consideration has been given each detail th^t it will 



I 



USE. 503 



do its work with a minimum of attention and reliability in operation. Particular 
attention has been paid to simplicity of details, as well as to their durability, and 
with steam as a power, the range of the wagon's distance of operation, or the 
distance that it can be run, is unlimited. 

We hope at an early day to give more fully the details of this company's 
wagons. 



Editor Compressed Air: 

It is proposed to run a horseless carriage by compressed air, and the ar- 
rangement is to construct a light vehicle on the bicycle principle with a good air 
motor, using air reheated from a steel bottle compressed to a high pressure of 
1,000 to 2,000 lbs.; this apparatus to be used for conveying persons from one point 
to another within a few miles. 

For the information of myself and other readers who favor air whenever 
it can be used, will you please answer the following: 

A pair of single-acting cylinders, 2^/2" diameter by 5" stroke, at 100 lbs. 
air. What power will this develop when air is heated so as to use it by expan- 
sion, and how long will a steel bottle of 2 cubic feet at 2,000 lbs., run the en- 
gine, and what horse-power will it take to charge the bottle? Also, what revo- 
lution per minute would the engine run at its full horse-power? Could the air 
be used without heating, and would it freeze up the engine? 
Leavenworth, Kan., July 16. w. j. e. carr. 

[Compressed air as a motive power has many economical and useful appli- 
cations, but it has its limitations. Our hope in this direction seems to be con- 
fined to the possibilities that might result from the use of liquid air. At present 
there does not seem to be much encouragement in the use of compressed air for 
motor carriages. The limited space attainable and the weight of the apparatus 
seems prohibitive. A steel tube of one cubic foot capacity with air at 2,000 lbs. 
pressure (say 9" diameter), will contain 268 cubic feet free air, and power re- 
quired to compress this quantity per minute will be 268 x .43 = 115 h. p. ; or if 
done in one hour's time, will be 2 h. p., and this calculation is based upon the 
very best type of 4 stage compressor with perfect intercoolers. 

A pair of 2^" x 5" single-acting cylinders operating at 100 lbs. pressure, 
require each 2)2 cubic feet free air when running at best speed (say 400 revolu- 
tions per minute), so that out of a storage reservoir of 2 cubic feet, you will only 
get a run of about four minutes. 

The weight of a Mannesmann steel tube 9" diameter, per cubic foot stor- 
age, is 82.2 lbs., and weight of i cubic foot air at 2,000 lbs., is 10.2 lbs., making a 
total weight of 92.4 lbs. for every 2 minutes the carriage will run. — Ed.] 



AUTOMOBILE COMPRESSED AIR FIRE ENGINE. 

The time is comparatively near at hand when every city will have its public 
•supply of air power, and when such a time arrives the utilization of compressed 
air will enter into almost every nook and corner of industrial, nuuiicipal and 



504 



USE. 



domestic enterprise. Its usefulness is so comprehensive that a central com- 
pressed air power plant might in these days look for a large and prosperous 
patronage. 

One of the most forcible arguments for introducing a public supply of 
compressed air will be the degree of economy and the vastly increased protection 
which would be afforded by compressed air in the matter of fires. It is entirely 
feasible to propel a fire engine to a fire without horses, and when it reaches the 
water supply to be operated by compressed air. 

Protection against fires is one of the most important municipal questions, 
and the expense to the public of handling a modern fire department is one that 




FIG. 169 — AN AUTOMOBILE COMPRESSED AIR FIRE ENGINE. 



requires skillful financial treatment to keep it within bounds, and at the same 
time, have an efficient department. 

A public supply of compressed air would certainly reduce the expense of a 
fire department to within a reasonable figure, and the proposition to introduce 
automobile compressed air fire engines will in time bring forth potent reasons for 
the adoption of this system. The installation of a compressed air supply would 
not have to be borne by the fire department, because private enterprise will be 
glad to install central compressed air power plants, relying on the patronage of 
the general public in the matter of power, but when the advantage of such a 
system is well known, any proposition to lay pipes in the streets for this purpose 



USE. 505 

will receive the moral support of every fire board and a majority of the citizens, 
all of whom are interested in fire protection. 

The plan to be followed is similar to that followed by the installation of 
gas and water plants. Mains would be laid in all streets, and air hydrants would 
be close to the water hydrants. 

An automobile carriage with a suitable fire pump would constitute a fire 
engine, to be propelled by compressed air, electricity, gasoline or other motive 
power. With such an apparatus, the time used in reaching a fire would be 
reduced to a minimum, and the operation of applying the air power for pumping 
the water would take but a few seconds. 

The advantage of this system, which does away with cumbersome boilers 
and dangerous progress through crowded streets with wildly excited horses, will 
be apparent to every one. If necessary, a speed of 30 miles an hour may be ob- 
tained in going to a fire and without any undue commotion. The weight of the 
vehicle itself would be very much reduced. An ordinary engine to be drawn 
by horses weighs about 8,500 lbs. and an equally efficient automobile engine will 
not weigh more than 5,000 lbs. or possibly less. 

As an illustration of possibly economy in a city, we will give the statistics 
of the fire department of Newark, N. J. 

The manual force of this department is 202 men with the following appa- 
ratus : Fourteen steam fire engines, 4 hook and ladder trucks, i aerial truck, i 
chemical engine, 4 engineer's wagons, 2 wagons for superintendent of fire alarm 
telegraph. In reserve are two steam fire engines, one hook and ladder truck, one 
chemical engine and one engineer's wagon ; and the cost of operating the depart- 
ment for one year is $251,000. Eighty-two horses are kept in this department, 
aggregating the value of upwards of $30,000, and the mortality among horses in 
fire departments is necessarily high ; consequently, there is a constant expense 
from this cause. 

Automobile fire engines should not cost more than ordinary fire engines. 
The number of men employed for taking care of horses would be dispensed with. 
No coal or other fuel need be used. 

The item of keeping the above number of horses would amount to $19,680 
a year, counting the expense of keeping one horse at $20 per month. The total 
saving in a department of the size of Newark, N. J., would probably reach $30,000 
a year, or about 7^ per cent, of the total cost of running the department. 

In the foregoing estimate no account is taken of the cost to the department 
for the use of the compressed air for operating engines which would be used 
during fires, and the reason for omitting it is because any company putting in a 
compressed air plant would readily concede the free use of power for such pur- 
poses in part compensation for the franchise privileges. But even if it had to be 
paid for at regular rates, the cost would not amount to much. 

The development of such a scheme is within practical limits and it only 
needs discussion and intelligent demonstration. 

The automobile fire engine shown herewith is simply the combination of an 
automotor with an ordinary pump mounted on it. It admits of any modification 
from the position of the pump, which may be vertical instead of horizontal, and 
the construction of the carriage, which may be propelled by any reliable power, 
preferably compressed air. 



5o6 USE. 

A RIGHT WAY AND A WRONG WAY TO PLACE COMPRESSED AIR 

IN COMPETITION WITH ELECTRIC POWER 

FOR STREET RAILWAYS. 

The indications being that compressed air will be experimentally used for 
practical street railway operation at an early day, it should be earnestly hoped by 
all friends of compressed air, and especially by those who are interested in its 
introduction as a motive agent, that it will be so experimentally introduced as to 
give a reasonably fair impression. The use of compressed air for street car pro- 
pulsion has hitherto been regarded with distrust and prejudice, for several rea- 
sons. It may be reasonably hoped that a fair trial of compressed air for this 
purpose, under circumstances that will do it justice, will, to a large extent, re- 
move this prejudice and draw attention to the advantages of such a motive 
power. A number of important requisites to the fullest success of a compressed 
air system for street railway operation might be profitably considered. These 
features vary somewhat in importance in different systems which have been pro- 
posed. There are, however, two considerations which apply with equal force to 
sll compressed air systems, and it appears desirable to draw attention to their 
miportance at this time. The two features referred to are, first, the pressure at 
which the compressed air is stored upon the cars, and second, the suitability of 
compressing apparatus for charging the cars. These two matters may properly be 
considered simultaneously. 

The only apparent practical method of using compressed air for street car 
propulsion is that known as the storage system. In every case where air is 
stored in reservoirs upon the cars for this purpose, the air is admitted to the 
motor cylinders at a moderate pressure and is stored in the reservoirs at a con- 
siderably higher pressure, in order to enable the car to be run some distance 
without renewing the supply of air. There are two ways of increasing the mile- 
age of a car with one stored charge of compressed air; one is to enlarge the 
reservoir volume for storage, and the other is to increase the pressure of the 
stored air. For practical reasons, the size and volume of storage reservoirs is 
limited and the temptation to store the compressed air at high pressures has con- 
sequently been great, in order to cover long distances with one supply of air. If 
the absolute pressure of the stored air be doubled, the available power, at the re- 
duced pressure for the motor, is doubled ; but in thus doubling the stored power, 
the cost of the compressed air supply has been very much more than doubled. 
After compressed air is stored in the reservoir, the temperature of that air be- 
comes practically the same as that of the external atmosphere. Each cubic foot 
of air so stored, at an absolute pressure of p pounds per square inch, has re- 
quired, in the process of compression and delivery into the reservoir, the expen- 
diture of work, which, in a properly designed compressor, is represented by 



sn ( r p 1 "-I ) 



In this formula, s represents the number of stages during compression, 
with complete cooling of the air to atmospheric temperature between each two 
consecutive stages; and n is a number not exceeding 1.408, and is usually a trifle 
less. 



USE. 



507 



If the air be subjected to no cooling influence whatever during compression 
in the air cylinder, the value of n is 1.408. For practical reasons, it is always 
customary, in compression plants of any considerable size, to water jacket the air 
cylinders, which exerts a cooling influence, in greater or less degree, upon the 
air during the period of compression. Where the compressing cylinders are 
very small, it is not improbable that the cooling effect, due to the water jacket, 
is a very material one ; but it has been fully demonstrated that where large com- 
pressing cylinders are used, as would be the case in a compressing plant of suit- 
able proportions to supply a street railway system with compressed air, the cool- 
ing influence of the water jacket upon the air during compression is quite small. 
In view of the fact that more or less loss occurs by leakage past the air piston 
and valves, it may, without any material error, be assumed that the cooling in- 
fluence of the water jackets about offsets these losses, and the valve of n should 
therefore be regarded as 1.408. 

The number of stages which should be employed for compression depends 
upon the final pressure and the quantity of air to be supplied. When a large 
quantity of compressed air is to be supplied at a high pressure, an economical 
performance of the compressor can only be obtained by compressing in several 
stages. For the purpose under consideration, the final pressure being 500 lbs. 
or more, the number of stages should not be less than three or four. 

Assuming that the compression occurs in four stages, the following table 
shows the foot pounds of work expended upon the air for each cubic foot of 
compressed air stored at atmospheric temperature and different storage pres- 
sures, from 500 lbs. to 2,000 lbs. Indicating by w the foot pounds of work which 

TABLE 49. 





Work Expended. 

(W) 


T3 
iJ 


.a 

W 


1-^ 

t/3 


Foot lbs. 


Rel've. 


.500 lbs. 
1,000 lbs. 
1,500 lbs. 
2,003 lbs. 


300 600 

724 100 

1 201 300 

1 714 800 


2!409 
3.997 
5.705 


1.000 w 
1.971 w 
2 943 w 
3.914 w 


l.COO E 
.818 E 
.736 E 
.686 E 



may be done in the motor by one cubic foot of air stored at 500 lbs. pressure, 
the table also shows the relative amounts of work that can be performed in the 
motor by one cubic foot of air stored at the various other pressures. Also, 
representing the efficiency of any system, when operating with a stored pressure 
of 500 lbs., by E, the table shows the relative efficiencies of the same system with 
greater pressures of storage. 

It will be seen from this table that the efficiency of the system diminishes 
very rapidly as the pressure of the stored air is increased. Whatever the system 
itself may be, and regardless of what its actual efficiency may be under any 



5o8 



USE. 



stated conditions, the efficiency of that system will vary somewhat more than is 
indicated by the table. The reason for this is that the greater the pressure of 
storage, the more difficult will it be to prevent loss by leakage, and consequently 
the incidental losses due to leakage, etc., will be increased by the higher pressures, 
with the result that there will be a greater difference in the actual efficiencies, 
with different storage pressures, than is shown by the table. 

To indicate the fact that the conditions are less favorable to economy for 
all storage pressures, but especially so for the higher storage pressures, when 
the air is compressed in a smaller number of stages, the following table has 
been prepared, for single stage compression : 

TABLE 50. 



t 




-c 




V 


Work Expendkd. 

(W) 


1^^ 


1 

'0 

W 


2^ 



35 


Foot lbs. 


Rel've. 


500 lbs. 
1,000 lbs. 
1.500 lbs. 
2,000 lbs. 


461 too 

1 217 500 

2 134 000 

3 169 600 


1.535 
4.050 
7.099 
10.544 


1 000 w 
1.971 w 
2.943 w 
3.914 w • 


.651 E 
.487 E 
.415 E 
.371 E 



It will be seen by a comparison of the two tables, that good commercial 
economy is absolutely out of the question without the use of suitable multiple 
stage compressing machinery. It will be equally evident that a system which 
might compare very favorably in point of efficiency with the electric trolley sys- 
tems, when operating under a storage pressure of 500 lbs., would be hopelessly 
out of competition in this direction if operated with a storage pressure of 
2,000 lbs. 

Attention is called to these matters more especially on account of the evil 
influence of the wholly incorrect and misleading statements which have been 
made by those who desire to befriend the use of compressed air. It has been 
stated, by at least one writer, that the increased cost of supplying compressed air 
for storage at high pressures is insignificant in comparison with the advantage 
of the increased mileage due to a single air supply. In comparing the cost of 
compressed air power with that of horse power for street railways, such a state- 
ment may perhaps be excusable; but in comparing compressed air with electric 
power, such a statement is absolutely unfounded and is extremely dangerous, in 
that it may be influential in condemning the use of compressed air altogether in 
the event of the failure of a high pressure storage system. 

It cannot reasonably be expected that the efficiency of the electric trolley 
system can be materially surpassed by that of a compressed air storage system 
operating under the most favorable conditions ; and it is certain that it cannot be 
nearly approached by a compressed air system which stores air at such high pres- 
sures as have been recently proposed, or in which the compressed air is supplied 
by anything but a high grade compressing plant. It will be far better to store 



USE. 509 

air at a moderate pressure and to attempt only a moderate car mileage between 
successive chargings. This will, in many cases, require additional charging 
points, which may be supplied either by additional compressing stations or by 
carrying the compressed air in pipes from a central compressing station to local 
charging stations; but there can hardly be any doubt that the cost of operation 
will, in the long run, be very much reduced by this plan. 

Nothing is now said regarding any collateral advantages in the use of 
compressed air for street railway operation ; it is simply desired to point out that 
there is a right way and a wrong way to place compressed air in competition 
with electric power. It is to be hoped that compressed air enthusiasts will not 
give the future of compressed air a black eye by adopting the wrong way. 

R. A. PARKE. 



POPP COMPRESSED AIR MOTORS FOR TRAMWAY TRACTION. 

The installations transmitting power by means of compressed air from 
central stations to an aggregate of 8,000 horse-power for a great number of indus- 
tries in operation in Paris, effect the transmission by means of canalisation, or 
miles of air mains laid in the "streets, with branches leading into workshops and 
other places where required. The successful operation of this system, invented 
and carried out by M. Victor Popp, induced him also to extend it to the supply 
of compressed air for tramway traction. 

It is impossible to better explain the position which compressed air as a 
motive power occupies than by quoting the report of Mr. Humblot, inspector- 
general of the Department of Bridges and Roads of France. In effect, he says : 

"Compressed Air is not a source of power. It is, in reality, only a vehicle 
for the transmission of power in heat, which heat can retransform itself into 
power. 

In order to obtain from air an economical return, it is necessary to supply 
it 'with caloric at the moment of its utilization, by re-heating, in order to com- 
pensate for the losses of every nature to which it has been subjected as as a con- 
sequence of cooling after compression in the tubes and reservoirs. 

By employing compressed air in traction, all the many advantages are se- 
cured which this agent has been demonstrated to possess in the mechanical appli- 
cations which have heretofore been made. 

If there is anywhere a demand for an easily manageable motor, it is cer- 
tainly for tramways. 

With compressed air, variations of speed are obtained with the greatest 
ease and without shock, by the simple turning of a cock; stops are made almost 
instantaneously, as vehicles operated by this system naturally employ air brakes, 
the reliability of which is so well known. 

Owing to the Popp system of feeding points along the line, a single power 
station can supply several lines at tht same time, becoming therefore a veritable 
central station for the entire network of tramways of a city, and at the same time 
distribute in a whole city mechanical energy as done now in Paris. The weight 
of the new Popp car, seating fifty persons, .is 16,000 pounds when empty. 



5IO 



USE. 



In order to gain a still higher economy, the motor is compound and the air 
is reheated twice. 

The motor being compound (or with two cylinders) can, according to its 
needs at various points of the route, work with either double or single expansion. 

By means of a special regulating apparatus, the several combinations by 
which the compressed air is admitted into the motor cylinders, for starting, regu- 




FIG. 170— COMPKESSEU AIK TKACTION IN PARIS. CHARGING STATION ON A 
PARIS TRAMWAY. 

lation of power and speed, stopping, and brakes, operate in a cycle perfectly 
established and controlled and with the greatest simplicity. 

'JMie various parts of the regulating apparatus are operated by a single 
handle and only require in consequence a siligle movement. 

The entire mechanism is hidden beneath the car body. The body itself 
remains completely independent of the frame upon which it rests. 

The platforms are entirely free. 



I 



USE. 



511 



The driver on the front platform has nothing whatever to do but to operate 
one controlling handle. 

The car runs equally well in either direction. At a terminus the driver 




FIG. 171— A COMPRESSED AIR CAR USED IN PARIS. POPP SYSTEM. 



512 USE. 

moves to the other platform, carrying with him the handle. The expense and 
inconvenience of turn-tables is thus avoided. 

MOTOR CAR. 

The frame and springs have a very strong, solid and well-built appearance, 
while the cylinders and all movable parts are inside, and placed between the 
wheels. The frame is suspended by leaf springs jointed to the axle boxes over 
the axle centres, while the body is suspended on leaf springs fixed to the end of 
the framework. This double suspension produces a gentle motion, and facilitates 
the passage of the car round sharp curves, even in the case of long car bodies. 
The two axles are connected by connecting rods. One of the axles is worked 
directly from the compressed air cylinder by means of wheel gearing, consisting 
of two wheels. The larger wheel is fixed to the wheel axle, the smaller one to 
the motor shaft, showing the frames of the compressed air cylinders with their 
piston rods, crank shafts, and the slides with their eccentrics — in a word, the 
whole mechanism. The above-mentioned gearing runs in oil enclosed in an oil 
box. The frame is of solid cast steel. The compressed air engine is designed 
on the compound system with varying expansion. (Meyer.) An attempt has 
been made in designing the machinery to arrange the various parts so that they 
should be easily accessible for repairs and removal if necessary. As the engine 
is worked on the compound principle it is-provided with two cylinders ; and the 
compressed air is heated during expansion and before entering the cylinders by 
means of a coke fire laid on a hopper arrangement which is filled once a day. 
The compound motor can be worked at double expansion or with direct admission 
of the compressed air in both cylinders. B}' means of a special disposition of the 
slide valves the compressed air can be worked at different degrees of expansion, 
by its variable admission into the cylinders ; whereby also the power of the engine, 
its speed, the stoppages, and operation of the brakes are perfectly regulated 
according to the requirements of the service. All these operations are carried 
out by means of the pair of levers at the driver's hands. As there are no heating 
vessels or any other machinery on the platform, these are perfectly free, and can 
be used for passengers — the carrying capacity of the motor car, is therefore, so 
much increased. 

AIR RESERVOIRS AND HEATER. 

The air flasks are fixed under the platform (fore and aft) and are charged 
for the St. Maur lines at 700 lbs. pressure. The chargement is made in less than 
one minute by means of a pipe emerging from a post at one side. The driver, 
without having to leave his machine, makes a joint which, by means of a valve 
and a differential valve piston, establishing the connection between the air pipe 
and the car tanks. Soon as the full charge is taken in the driver shuts the ad- 
mittance valve, cuts off the connection with the post and through the loss of pres- 
sure the valves close the connection with the pipe and the car goes along without 
any loss of time. From the air reservoir the compressed air goes first through 
a pressure regulator, passed to the heater, then to the small cylinder returned to 
the heater and then to the large cylinder and last through the exhaust pipe. In 
the heater the air is each time heated to 200 C. 

The Popp tramways carry compressed air flasks made of specially prepared 
steel under and, if necessary, on top of the carriage. The flasks have been made 



NC^TT^vT'r^^"- 



USE. 



513 



to withstand a pressure of 4,000 lbs. to the square inch. The maximum working 
pressure used for the cars in St. Maur is 700 lbs. The air for the cars is com- 
pressed by three 150 horse-power compressors. The storage capacity of the com- 




FIG. 172. — MECHANICAL TRUCK AND FRAME READY TO RECEIVE THE CAR BODY. 

THE POPP SYSTEM. 



514 USE. 

pressed air flasks on the Popp car with a maximum working pressure of 2,000 lbs. 

would be enough to run the car 36 to 40 miles. 

CONTROLLING THE CAR. 

One of the features of the Popp car is the working of the motor and air 
brakes. All the required moves which can be asked from a street car are made 
instantly, as easily and without possibility of mistake on the part of the motorman 
as can be imagined. The car conductor has before him one wheel and two small 
handles immmediately below. The use of the left handle is to reverse the motor 
movement. The right handle to open and cut off the air admission and commands 
also the safety brake. The wheel commands — ist, the air brake at variable pres- 
sure; 2d, the progressive admission to the small cylinder (high prssure) ; 3d, 
the direct admission to the small and to the large cylindler (low pressure). The 
various operations are made with one turn of the wheel. It will be remarked by 
this that whenever the motorman wants to use the brake before the brake came in 
use automatically the admission is entirely cut off both in using the safety and 
variable brake through the handle or the wheel. Outside of these two brakes the 
Popp car is furnished with an ordinary hand brake. 

TRACTION AND CONSUMPTION OF AIR. 

The motor is capable of slipping the wheels on a dry rail under weight of 
36,000 lbs. The air consumption of the car running on the Saint Maur les Fossees 
(Seine) lines (3 per cent, ascent) varies from 25 to 35 lbs. per mile. The car 
runs 10 miles at a speed from 12 to 20 miles an hour. 

COST OF PRODUCTION OF COMPRESSED AIR AND ITS UTILIZATION AS A MOTIVE POWER 

FOR TRAMWAYS. 

The cost per horse-power-hour in compressed air reduced to atmospheric 
pressure and utilized by motors of from 15 to 50 effective horse-power, has been 
established by numerous trials in Paris. Motors of the above power are princi- 
pally employed in mechanical traction for tramways. The consumption of air in a 
compound motor such as is employed in the Popp car, the air being re-heated 
before its admission to the cylinder to a temperature of 200 C, involved losses 
in the pipes, small escapes such as may happen in the mechanism, and also cost of 
operating the wheel brakes, is 30.577 lbs. in compressed air reducing to atmos- 
pheric pressure. One steam horse-power-hour at the station where the air is 
compressed at a pressure of 853 lbs. equals ii lbs. air reduced to atmospheric 
pressure. For reheating the air per mile car, 0.50 lbs. coke. 

CONCLUSIONS. 

It is clear that system of mechanical traction for tramways will have 
chances of adoption proportionate to its gain in economy of operation ; reduction 
in expense being desirable at once in cost of production at the station, in the 
motor, and in the consumption by the motor of power. 

But it is also necessary that the system be easy to work and direct, and 
moreover absolutely beyond the possibility of sudden interruption from accident. 
(In Paris, compressed air without interruption during 13 years.) 



fTrs^-y"..' 



USE. 



515 



It is also necessary that the system proposed should be easily understood 
by any tramway operator, and that it should not be necessary to preface its con- 
sideration by long special technical study. 

In the present state of the art of mechanical traction as applied to tram- 
ways, it is evident that if economical operation be desired, the supply of power 
from a central station is indispensable. 

Operation by electric conductors carries with it many difficulties for the 
operator, largely arising from the inevitable complications of a service requiring 




FIG. 173 SIDE VIEW OF MOTOR AND TRUCK. THE POPP SYSTEM. 



such special knowledge as to make an expert technical staff in constant sur- 
veillance a necessity. 

With compressed air the method of operation is so simple that there is no 
necessity for long study of an expert nature before undertaking the handling of 
that system, while it is at the same time so regular and sure that one is not kept 
constantly on the alert as is the case with the electric line. 

It follows that the manager of a compressed air tramway can really direct 
its operation without being always at the discretion of an engineering staff, since 
he is free from apprehension of any serious trouble in his service. . 

To handle an air compressor is as simple as a pump. Any ordinary me- 
chanic can undertake its management. 



5t6 use. 

The air being stored in advance in great quantities at a time in the reser- 
voirs of the central station — in the distributing pipes, and in the tanks of the 
motor — interruption of service is practically impossible. 

One of the most important advantages of compressed air is that it lends 
itself so well — incomparably better than any other system — to direct storage, 
which quality admits of holding in reserve great accumulations of energy with so 
much ease and economy. So far as accumulation of reserve power is concerned, 
electricity has incontestibly shown itself greatly inferior to compressed air. 



COMPRESSED AIR LOCOMOTIVES. 

Under certain conditions in mines or in warehouses where smoke or fire 
is undesirable, locomotives propelled by compressed air have performed useful 
service. At Vivian, W. Va., certain of them have been put at work. The new 
locomotives are approximately lo feet 5^ inches long, 5 feet 8 inches wide 
and 4 feet 5 inches high, and weigh TO,ooo pounds.. It will readily be seen from 
these figures that they are adapted for running in very small openings. The cyl- 
inders are 5 feet 10 inches, and the driving wheels, of which there are four, are 
23 inches in diameter. The storage tank has a capacity of 47 cubic feet of air and 
a working pressure of 535 pounds per square inch, and there is also an auxiliary 
reservoir. The locomotive main tank is designed for 600 pounds, but the work- 
ing pressure for the service intended is about 535 pounds. A three stage com- 
pressor is used, pumping into a 3-inch pipe line, which serves to connect the com- 
pressor to the most convenient point of charging the motors, and also acts as an 
air reservoir, the compressor and pipe line being competent to withstand a pres- 
sure of 850 pounds. 

These locomotives, which take the place of mules, are to be used in side 
entries and in making up trains in the rooms of the mine and delivering the 
trains to the main entry, where they are handled by steam locomotives. The 
average length of each side entry is 4,500 feet, with grades of i^ per cent, in 
favor of the loaded cars. The gauge of the track is 3 feet 8 inches, the weight 
of the rails 16 pounds per yard and the radius of the sharpest curve 24 feet. The 
locomotives are designed to make the round trip of 9,000 feet, with six cars, with 
one charge of air and to work on curves of 15 feet radius. The weight of the 
loaded cars is about 8,500 pounds. 

This is said to be the first introduction of any kind of mechanical haulage 
anywhere for sole use in butt entries and rooms. The low cost of installation 
and operation and the greater adaptation to the conditions of the service and 
requirements caused the pneumatic system of haulage to be adopted in prefer- 
ence to electric haulage, although an electric plant had already been determined 
upon for working the mining machines. From the -Coal Trade Journal. 



THE COMPRESSED AIR LOCOMOTIVE. 

There seems to be no question about the utility and economy of compressed 
air locomotives, for they are in use in many places at the present time and new 



v#'"..--^ -. , 



USE. 517 

installations are being built where such locomotives will be used much more ex- 
tensively than now. Stationary engineers are not practically interested in com- 
pressed air locomotives, but compressed air as a motive power is being introduced 
for a great variety of purposes where it is found economical and quite convenient. 
Many of the steam plants in office buildings include compressed air machinery of 
one kind or another in their equipment, and owing to the great difference in econ- 
omy of the different kinds of air compressors and the method of utilizing the 
compressed air, the stationary engineer will find it to his convenience and benefit 
to learn as much on this subject as he can, for its application will become more 
extensive and the methods of utilizing it in the office buildings more numerous 
each year. 

The compressed air locomotive has an ungainly appearance because it 
differs from what we are familiar with. The absence of a smokestack makes it 
look as though it was not all there, but for work and economy it leaves but little 
to be desired. We shall also find that compressed air machinery about the plant 
can J)e utilized for many purposes with a greater degree of economy than some of 
the steam-actuated devices now being employed, although they may for a time 
appear out of place when being operated side by side with steam machines. — 
National Engineer. 



Mr. J. A. Eisenaker, of Elmira, N. Y., is responsible for the following, 
which appeared in Locomotive Engineering: 

"I send you sketch of a small engine, driven by compressed air, which is 
designed for driving boring bar, for boring out locomotive cylinders, or a small 
lathe or planer, in case of necessity. 

The bed plate rests on four wheels, so it can be easily moved wherever 
wanted. Two blocks are put under the bed plate and fastened to the floor. 
After being put in line with pulley on boring bar, the air hose is connected and 
the jengine is ready for operation in either direction. 

The full air pressure follows the piston to or nearer its dead point, and 
can be run to most any speed. The valve is very simple in construction — is a 
square piece of cast iron (length according to length of cylinder) ; the ports for 
taking or releasing air are drilled with a j4-in. drill, also ports B and C in 
cylinder, and A and D outside of cylinder, for release. 

The valve is surrounded by air ; a couple of holes are drilled through top of 
valve, to let air in to the inner part of valve XX. 

It will be seen that the air chest is cast on cylinder and projects over both 
ends of cylinder, and the air-chest cover is fastened on with top bolts. 

The valve-reversing arm E causes the movement of the valve, and is regu- 
lated by set screw collars SS, to the required stroke of valve, which will be 
somewhat cushioned, and also the piston, when same comes near its end of 
travel. 

The piston rod extends through back end of cylinder, and on its front end 
is directly connected to the crank pin, which of course gives the oscillating move- 
ment." 



5i8 



USE. 



The city of Camden, N. J., owns Its own system of water supply. The dis- 
posal of sewage in the Delaware River from adjacent towns caused the water of 
that stream to be objectionable. The water is now taken from driven wells, and 
the system has a capacity of 20,000,000 gals, every 24 hours. The wells are 
arranged in four (4) groups surrounding the pumping station, three (3) of which 
are operated by pumping and one (i) by compressed air. Three of these groups 
of wells are close to the pumping station, and the fourth group is located over 
4,000 feet from the pumping station. This group consists of ten wells 8 and 10 
in. in diameter. They are operated by compressed air under a pressure of about 
47 lbs. per square inch. The air .is furnished by an Ingersoll-Sergeant^ com- 
pressor having a steam cylinder 18 inches in diameter, an air cylinder 22 inches 
in diameter and a stroke of 22 inches. The receiver is 10 ft. 6 in. long and 4 ft. 
6 in. in diameter. The air is conducted from the receiver to the wells through a 
pipe 7^ in. in diameter, decreasing to 4 inches at the last well. The air pipe 
down each well is i^ in. in diameter, with about 60 per cent, submergence, and 




FIG. 174 — OSCILLATING AIR ENGINE. 

the air escapes through holes in the lower portion. At the head of each well is 
a broad quarter-bend connecting with the main discharge pipe, and the air pipe 
passes into it through the flanged shoulder. 



THE COMPRESSED AIR LOCOMOTIVE ON THE N. Y. ELEVATED R.R. 

Compressed Air has not been enthusiastic in advocating the recent experi- 
ments in air traction on the New York Elevated Railroad. These experiments 
as far as they have been conducted, have demonstrated two points clearly. In 
the first place, it has been shown that air can b*e compressed and stored econo- 
mically and safely at 2,500 pounds pressure. Never before has a compressing 
plant on so large a scale and. of so high a class in design been applied and tested 
for any such service as this, nor has there ever been, to our knowledge, a case 
where air has been stored at 2,500 pounds pressure at so low a cost as in the 
generating plant used in this instance. It has also been demonstrated that this 
air can be used with reasonable economy in a motor which will pull a train of 
loaded cars between the Battery and Central Park and return. That this can be 



USE. 519 

(lone at less expense in fuel and labor than the present system of steam locomo- 
tion, is a fact about which there will be little dispute. The locomotive is wasteful 
in fuel because its engine utilizes only a small portion of energy within the 
steam; the high pressure exhaust indicates this lack of steam economy. In the 
case of air produced by compound condensing Corliss engines, we have a horse- 
power produced at an expenditure of about 2 pounds of coal as against 6 or 8 
in the locomotive. This air when used is cut off and expanded in the motor and 
thus its power is not wasted. But it is not a question between air and steam, but 
between air and electricity. Both can beat the present system, but in the present 
condition of pneumatic traction it does not appear to us wise to attempt a case 
like the Elevated Road until after pneumatic tramcars have been developed and 
perfected. From an engineering point of view, it would seem easier and safer 
to develop motors for carrying passengers in street cars first and then lead up to 
larger things. From the business point of view, the street car field is broader 
and offers greater opportunity for profit. It would also seem that this field 
might be cultivated and developed to a paying point at considerably less expendi- 
ture, and in a matter of this kind, which at best must be expensive in experimental 
work, it is wise to count the cost, lest the experiment fail through want of funds, 
even though its success from a mechanical standpoint is assured. 



I 



COMPRESSED AIR HAULAGE PLANT AT NO. 6 COLLIERY OF THE 

SUSQUEHANNA COAL COMPANY AT GLEN LYON, 

PENNSYLVANIA.* 



(The No. 6 Shaft plant was put in operation in September, 1895, and the No. 6 
Slope Motor in May, 1896.) 
The plant consists of one Norwalk Three-Stage Compressor, 12^", ^Vi" 
and 5" diameters air and 20" diameter steam cylinder, all 24" stroke, capacity at 
100 revolutions 296 cubic feet free air per minute, compressed to 600 lbs. per 
square inch. Main pipe ^" diameter, 4390 feet long, with five charging stations 
in No. 6 Shaft, and a branch of 3" pipe 3100 feet long, with three charging sta- 
tions in No. 6 Slope. Each of these- two lines charges a Porter Compressed Air 
Motor with 7" x 14" cylinders, four 24'' drivers, weight about eight tons, with a 
tank capacity of 130 cubic feet of air at 550 lbs. pressure in the main tank, re- 
duced to 160 lbs. in the 8" auxiliary tank, 4.2 cubic feet capacity supplying the 
cylinders. The No. 6 Shaft run averages 4000 feet each way on grades of Yz 
per cent, to 2^ per cent., and averaging close to i per cent, in favor of the loaded 
cars. The No. 6 Slope run averages 2100 feet, with nearly the same grades. 
The mine cars weigh 2800 lbs. empty and about 9800 lbs. loaded, and are hauled 
in trips of 12 to 20, averaging about 15 cars. The Shaft motor now hauls about 
355 and Slope motor 320 cars per day of ten hours. Replacing in the No. 6 
Shaft 17, and in the No. 6 Slope 15, total 32 mules, against 27 mules replaced 
in 1896. 



I 



♦Paper read at August meeting American Institute Mining Engineer ^ 



520 



USE. 



The average daily car and ton mileage of each motor was as follows : 

Tons Hauled One Mile. 
1896 1897 1898 

Empty, in 336 330 338 

Loaded, out.. 1180 1155 1183 



Cars Hauled. 
1896 1897 1898 

No. 6 Shaft Motor 355 3474 356 



Total 1516 1485 1521 

Net load... 844 825 845 

No. 6 Slope Motor 288 288.7 3i9-2 Empty, in 143 144 160 

Loaded, out. . 501 504 560 

Total 644 648 720 

Net load... 358 360 400 

Total both motors, gross (including empties returned) 2160 2133 2241 

Net load 1202 1185 1245 

The use of steam and air in compressor and motor operation as found by 
test was as follows: 

STEAM. 

Indicated H. P., compressor @ 130 revolutions 150 H. P. 

Steam consumption per H. P. per hour, from cards 34 lbs. 

Steam consumption per hour, from cards 5100 lbs. 

Steam consumption per hour, including condensation in line. .5200 lbs. 

Boiler H. P. required 174 B. H. P. 

Evaporation per pound of coal (cylinder boilers) 5 lbs. 

Coal required per hour 1040 lbs. 

Coal required per day, 10 hours 10,400 lbs., 4.65 tons 

Cost of fuel and firing per day, 10 hours, 4.65 tons @ 50c $2.32 

AIR. 

COMPRESSOR CAPACITY. 

Free air compressed per revolution of compressor, 2.96 cu. ft. (from calcula- 
tion by Norwalk Iron Works Co., no allowance for leakage). 
The compressor works 12 hours per day to 10 hours for the motors. 

Free air per min. at rated speed 100 revs. . .* 296 cu. ft. 

Free air per min. at actual speed 131 revs 387.8/10 cu. ft. 

Free air per day, 12 hours at rated speed, 100 revs 213, 120 cu. ft. 

Free air per day, 12 hours at actual speed, 131 revs 279, 216 cu. ft. 

CAPACITY OF AIR MAINS USED AS RESERVOIR — 

5 inch line 4380 feet 608 cu. ft. 

3 inch line 3100 feet 159 cu. ft. 

Both lines 767 cu. ft. 

At 600 pounds pressure these lines hold 32,505 cu. ft. free air ; capacity of 
main and auxiliary tanks 134.6 cu. ft. at 508 lbs. pressure (at which pressure they 
will equalize with main starting to charge at 600 lbs.), 4845 cu. ft. free air. 



USE. 



521 



LEAKAGE OF AIR MAINS. 

Loss of pressure standing 12 hours, from 550 to 350 lbs. 

Cu. ft. free air lost 11,688 cu. ft. in 12 hours,— 974 cu. ft. per hour. 

Percentage of leakage to total air compressed, 418/100%. 

AIR USED BY MOTORS. 

(From test of March 29, 1900.) 

Shaft Motor. Slope 

No. 2 Plane. No. 3 Plane. Motor. 

Number trips empty 3 lO ^^ 

Number trips loaded 3 10 15 

Average cars per trip, empty 15 i-3 12 7/10 il 4/10 

Average cars per trip, loaded 13 ^3 ii 3Ao 

Average cu. ft. free air per trip, empty 1724 5686 1230 

Average cu. ft. free air per trip, loaded 163 1 1898 599 

Average cu. ft. for round trip 3355 75^4 1829 

SUMMARY OF DAY's WORK, 1898. 

Shaft No. 6, 356 cars per day, 

6 trips, IS cars No. 2 Plane 20,130 cu. ft. 

20 trips, 13 2/10 cars No. 3 Plane 151*830 cu. ft. 

Slope No. 6, 320 cars per day, 

28 trips, II 4/10 cars, average 5i>2i2 cu. ft. 

223,022 cu. ft. 

Free air apparently compressed as above 279,216 cu. ft. 

Per cent, accounted for 83 4/10 % 

The difference 16 6/10% is due to leakage and slip in compressor, leakage 
of air lines and to changes in temperature. 

AIR USED PER TON MILE. 

Gross. Net. 

Average free air used per ton mile, No. 6 Shaft Motor 113 cu. ft. 203 cu. ft. 
Average free air used per ton mile. No. 6 Slope Motor 71 cu. ft. 128 cu. ft. 
Average free air used per ton mile, both motors 100 cu. ft. 180 cu. ft. 

The greater quantity of air used by the Shaft than by the Slope Motor is 
be to the heavier curves and the switching required, especially at No. 2 Plane, 
rhere a portion of the trip is frequently left. 

COST OF PLANT, NOT INCLUDING STEAM BOILERS. 

>mpressor $2,880.00 

Extras for compressor repairs 75-75 

Jhaft Motor 2,743.63 

>lope Motor 2,918.20 

Lxtras for motor repairs 207.93 

dr connections, $" line (6000 feet) 2,914.3a 



522 USE. 

Air connections, 3" line (4000 feet) 1,240.46 

Steam connections, compressor 278.27 

Material for compressor foundations and house, and air washing box. . 295.27 
Labor, compressor house and foundations, and 5" line, and installing 

Shaft Motor 1,183.01 

Labor, 3'' line and installing Slope Motor 46.95 

Foster equalizing valves 372.21 

Total cost of plant $15,156.00 

COST OF OPERATION OF PLANT. 

1897 1S9R 

Operating Expenses. 179 Days Worked. 160 Days Worked. 

Per Day. Per Yr Per Day. Per Yr. 

2 motor engineers, @ $2.10 $4.20 $751 -80 $4.20 $672.00 

2 brakemen, @ $1.60 3.20 572.80 3.20 512.00 

Yi one engineer compressor, @ $2.32 1.16 207.64 1.16 185.60 

Oil for compressor 67 1 19-49 -47 75-94 

Oil for motors 25 45.08 .25 40.94 

Repairs for compressors (material) .10 18.76 .48 76.08 

Repairs for compressors (labor) 06 10.38 .09 15.22 

Repairs for motor (material 16 28.78 .51 81.08 

Repairs for motor (labor) 18 2>2-77 .23 36.87 

Steam for compressor, 150 H. P., fuel and ' 

firing 2.32 41528 2.Z2 371.20 

Total operating expenses $12.30 $2,202.78 $12.91 $2,066.93 

Fixed Charges. 

Interest, repairs and depreciation, 174 H. P. 

boilers $1.46 $261.00 $1.63 $261.00 

Interest and depreciation of plant, 10% on 

$15,156.00 8.47 1,515-60 9.47 1,515-60 

Total fixed charges $9.93 $1,776.60 $11.10 $1,776.60 

Total cost 2 motors, J^ for each 22.23 3,979-38 24.01 3,843.53 

Estimated cost per day, 300 days' work 18.22 5,466.60 18.83 5,649.60 

THE COST PER TON MILE. 

1897. (179 Days). 1898. (160 Days). 

Daily Daily Per Ton Daily Daily Per Ton 
Mileage. Cost. Mile. Mileage. Cost. Mile. 
No 6 Shaft Motor, gross ton mileage. .1485 11. 12 75/iooc 1527 12.00 79/iooc 

No. 6 Shaft Motor, net ton mileage 825 11.12 1.35/iooc 845 12.00 1.42/iooc 

No. 6 Slope Motor, gross ton mileage.. 648 11. 12 1.72/iooc 720 12.00 1.67/iooc 

No. 6 Slope Motor, net ton mileage 360 11. 12 3.09/iooc 400 12.00 3.00/iooc 

Both motors, total gross ton mileage., .2133 22.30 1.05/iooc 2241 24.01 1.07/iooc 
Both motors, total net ton mileage 1185 22.30 1.89/iooc 1245 24.01 1.93/iooc 



USE. 523 

THE COST OF MULES DISPLACED BY THIS PLANT. 

No. 6 Shaft, 17 @ $126.64 $2,152.88 

No. 6 Slope, 15 @ 126.64 1,899.60 

$4,052.48 
OPERATING EXPENSE BY MULES. 

rO. 6 SHAFT. 

1897. (179 Days). 1898. (160 Days). 

Per Per Per Per 

Day. Year. Day. Year. 

Depreciation and interest on 17 mules @ 25% $3.01 $538.22 $3.36 $538.22 
Feeding, attendance, harness and repairs 

©$141.40 13.43 2,403.80 15.02 2,403.80 

Six drivers 9.40 1,682.60 9.40 1,504.00 

Six couplers and spragmen 8.10 1,449.90 8.10 1,296.00 

Total cost by mules $33-94 $6,074.52 $35.88 $5,742.02 

Cost by motor 11. 12 1,989.69 12.00 1,921.77 

Saving by compressed air $22.82 $4,084.83 $23.88 $3,820.25 

). 6 SLOPE. 

Depreciation and interest on 15 mules @ 25 % $2.65 $474-90 $2.97 $474-90 
Feeding, attendance, harness and repairs 

@ $141.40 11.85 2,121.06 13.26 2,121.06 

Five drivers 8.00 1,432.00 8.00 1,280.00 

Five couplers and spragmen 6.85 1,226.15 6.85 1,096.00 

Total cost by mules $29.35 $5,254.11 $31.08 $4,971.96 

Cost by motor 11. 12 1,989.69 12.00 1,921.77 

Saving by compressed air $18.23 $3,264.42 $19.08 $3,050.19 

"OTH NO. 6 SHAFT AND NO. 6 SLOPE. 

Total cost by mules $63.29 $11,328.63 $66.96 $10,713.98 

Total cost by motors 22.23 3,979-38 24.01 3,843.53 

Saving by compressed air $41.06 $7,348.25 $42.95 $6,870.45 

Total saving in two years $14,218.70 

Total cost of plant 15,156.00 

At the average rate of saving for 1897 and 1898 the entire cost of plant 
would be saved in 361 woi'king days. 



524 USE. 

COST PER TON MILE BY MULES. 

NO. 6 SHAFT. 

189T Tonnage. 1808 Tonnage. 

Ton p-^x Per Ton Ton p_„x Per ton 

Mileage. ^^^'- Mile. Mileage. '""'"- Mile. 

Gross ton mileage 1485 $33-94 2.29/iooc 1527 $35-88 2.35/iooc 

Net ton mileage. . .• 825 33-94 4.11/iooc 845 35-88 4.25/iooc 

NO. 6 SLOPE. 

Gross ton mileage 648 29.35 4-53/iooc 720 31-08 4.32/iooc 

Net ton mileage 360 29.35 8.15/1000 400 31.08 7.77/iooc 

TOTAL. 

Gross ton mileage 2133 63.29 2.98/iooc 2241 60.96 2.98/iooc 

Net ton mileage 1185 63.29 5.34/iooc 1245 60.96 5.38/iooc 

COST BY MOTORS. 

Total gross ton mileage 2133 22.30 1.05 2241 24.01 1.07/iooc 

Total net ton mileage 1185 22.30 1.89 1245 24.01 1.93/iooc 

SAVING BY COMPRESSED AIR. 

Gross ton mileage 40.99 1.93/iooc 36.95 1.91/iooc 

Net ton mileage 40-99 3-45/iooc 36-95 3-45/iooc 



The capacity of the Shaft Motor is equal to fully double its present work, 
while the Slope Motor is working at but about one-third of its capacity, while 
the compressor is doing all that it is capable of, and a second one was ordered 
April 7th, 1900. To operate the plant to the full capacity of both compressors, 
which, under the present conditions, would be about 4,500 ton miles gross, or 
2,500 net, per day for 300 days per year would bring the cost of operation, includ- 
ing fixed charges, to about $24.60 per day, or 547/1000 cents per ton mile gross, 
and 984/1000 cents per ton mile net load. While if all the work could be done 
by one motor under the No. 6 Shaft conditions up to the capacity of the com- 
pressor for 300 days per year, using only one crew, the cost of plant would ap- 
proximate $11,000.00, and the operating expense, including fixed charges, $10.86 
per day for 2,400 gross ton miles, equal to 45/100 cents per gross ton mile and 
81/100 cents per net ton mile. 

A further reduction of cost could be made by reheating the air at the 
motor by passing it through water at the temperature of steam at 90 pounds pres- 
sure, by which method tests have shown a gain of about 50% in air economy. It 
is probable that by this means, one motor could be run to its full capacity about 
3,000 gross ton miles per day with one compressor at a total cost of $10.80 per 
day, or 36/100 cents per gross ton mile, for 300 days' work per year ; the saving 
of 9/100 cents per gross ton mile, or about 20% over the last mentioned condition, 
being due only to the greater air economy, the fixed charges and labor cost 
remaining practically the same.— J. H. Bowden, C. E. 



USE. 525 

THE PROPOSED UNDERGROUND RAILROAD IN NEW YORK. 

Those who object to the proposed Underground Road in New York, on 
the basis that all underground roads and tunnels are disagreeable places, do not 
make allowance for recent improvements in construction, ventilation, lighting and 
traction. 

In building a tunnel through Broadway, every machine can and should be 
operated by compressed air. Power might readily be generated 'in the basement 
of a building along the line of the street and transmitted through pipes to the 
hoists, pumps, drills and excavators. There need be no disagreeable puffing of 
steam, smoke, or moving about of heavy boilers with their attendant loads of 
coal, water and ashes. There will be nothing experimental about this, because 
it has been done on the Chicago Diainage Canal, on the new Croton Aqueduct, 
and on hundreds of other places of less importance. 

Why talk about difficulty in ventilating a road under Broadway, when each 
train can be pulled by a compressed air locomotive which will puff dry, cool and 
fresh air into the tunnel at each stroke? The H. K. Porter Co., of Pittsburg, 
has built and put into successful operation engines for such duty as this. Imag- 
ine the trains as close together as those on the elevated roads, and it is not dif- 
ficult to see the wholesome effect of the locomotives puffing pure air into the 
tunnel. Compressed air for this purpose should be produced by compound or 
stage compressors. This is not only an economical condition, but it prevents 
the oily or burnt odor sometimes noticed in mines which receive compressed air 
from the common type of non-compound compressor. Mr. E. J. Farrell, the 
experienced contractor who built the Baltimore tunnel, claims that the whole- 
some effect of compressed air exhausted into a tunnel is greater than that pro- 
duced by any other means of ventilation. He has found that the exhaust from 
six rock drills is better than the effect produced by a No. 6 Baker blower. The 
six drills deliver about five hundred cubic feet of free air per minute, while the 
capacity of the blower is four thousand five hundred cubic feet. In the case of 
the drill, the air does work before it is exhausted into the tunnel ; hence its heat 
is converted into mechanical energy. The blower simply supplies fresh air from 
the outside and at normal conditions of temperature and pressure. 

Chief Engineer Parsons has planned wisely in keeping the tunnel as near 
the street as possible. It will be more accessible, dryer and more easily lighted. 
A waterproof lining will keep out the moisture. Compresed air, which should 
be on tap all along the line, might be used to light the tunnel on the Wells' light 

)rinciple. This light is now a familiar one in public works, its great luminosity 

)eing very marked. The light is more diffused than the electric or any other 
light. As the combustion is fairly complete, there is not likely to be any injury 
to the ventilation, though the light might serve the double purpose of lighting 

ind ventilation by being placed directly under vents or chimneys, and thus eject- 
ig large volumes of air from the tunnel. 

In the light of recent improvements, there is nothing mysterious or difficult 

ibout the construction and operation of underground roads. 



526 



USE. 



. 



ELECTRIC COTTON HAULER AT PORT CHALMETTE, LA. 

There has recently gone into operation an interesting electric freight haul- 
ing road at Port Chalmette, La., of which we give several views in the accom- 
panying engravings. 

Port Chalmette is the big cotton handling port recently constructed just 
below New Orleans on the Mississippi. At this point over $3,000,000 has been 
expended in cptton sheds, warehouses, compresses and wharves. The whole 
forms a town to itself, lighted by its own electric lighting plant, with arc lights 
and 220-volt incandescent lamps. Connecting the sheds, warehouses, compresses 
and wharves is a system of narrow gauge tracks for handling the cotton. 

The original promoters adopted compressed air locomotives for the work 
of hauling the cotton about from point to point. At the beginning of the cotton 




FIG. 175 — COMPRESSED AIR LOCOMOTIVE, PORT CHALMETTE, LA. 



season last fall, although four air locomotives were in service, they were unable 
to cope with the handling and moving of the cotton. The managers were skep- 
tical regarding electric traction, and the underwriters were afraid that electric 
motors would increase the fire risk. Something had to be done, and done 
quickly, to handle the large consignment of cotton daily received. A temporary 
trolley line was constructed and an electric truck provided. An engine and rail- 
way generator were hastily secured, and inside of ten days the most important 
part of the hauling work was being successfully handled by the improvised 
trolley plant. Its working satisfied both the Chalmette managers and the under- 
writers, and the result was a contract, was made for four electric haulage loco- 
motives. The apparatus was rapidly installed, and by the middle of the cotton 
season the trolley had supplanted the compressed air locomotives and was taking 
care of the large and extended haulage system of the entire terminal. 



USE. 



527 



The locomotives are "factory trucks," equipped with two NWP— 12 mo- 
tors, and weighing approximately 15,000 pounds; each is capable of hauling 150 
tons on a straight level track. 

Current is furnished by a 500-volt railway generator direct coupled to a 
300 H. p. Erie City Iron Works engine. The electrical apparatus was furnished 
by the General Electric Co., through Mr. J. J. Britton, of the New Orleans office. 




FIC. 176 — COTTON TRAIN AT PORT CHALMETTE — COMPRESSED AIR LOCOMOTIVE. 

'I hert; are about eight miles of 36-inch gauge-track about the cotton sheds, 
storage warehouses and wharves. — Electrical Engineer. 



Editor Compressed Air: 

Dear Sir: My attention has been called to an article in "The Electrical 
Engineer" of February i7lh, 1897, entitled "Electric Cotton Hauler at Port 
Chalmette, La." As Chief Engineer and General Manager, I planned the entire 
works of Port Chalmette, and the Belt Railway around New Orleans, and in the 
same capacity I planned and had built a compressed air plant equipped with 
pneumatic locomotives, to do the cotton hauling and handling at that port. 

During my management these pneumatic locomotives and compressed air 
system gave entire and complete satisfaction. Repeated tests were made and the 
results fully described at the time in different technical journals. 

I resigned last summer to go to Europe, and during my absence the engi- 
neering department and the power plant at Chalmette fell into the hands of a 
person who had never heard of compressed air until he accidentally happened 
to see the plant at Port Chalmette. The Chief Engineer was a very good man, 



528 USE. 

who had graduated in the science of engineering as levelman of a cotton com- 
press. 

As near as I can learn, it appears that, for instance, he attempted to run 
the plant without opening the valves supplying the compressed air to the loco- 
motive tanks. At all events, the compressed air plant which up to that date 
had been a perfect success, all at once appeared inefficient, and the local directors 
(their inexperience can be readily pardoned), in their anxiety to keep things 
going, sent for and used electric motors as described in said number of "The 
Electrical Engineer." 

These electric motors have about one-third of the hauling capacity of the 
pneumatic locomotives, are more expensive on account of the fuel consumed, and 
have the ever present danger of sparks in a cotton yard. 

As soon as the end of the cotton season permits any changes to be made 
at Port Chalmette, the compressed air plant there will again receive prompt at- 
tention. Yours very truly, 

A. W. SwANiTz, Consulting Engineer. 



COMPRESSED AIR AND ELECTRICITY AT PORT CHALMETTE. 

A writer who signs himself "G. F. P.," communicates with the Railroad 
Gazette regarding the Electric Haulage plant at Port Chalmette, La., a descrip- 
tion of which is given on page 526. 

The above journal has the following to say in regard to his communica- 
tion. 

"We have great confidence in the good faith and good judgment of the 
gentleman who writes the account of the Port Chalmette enterprise; and 
it is obvious that he is a good observer. We cannot agree with 
him, however, that the economy of the electric haulage as compared with 
compressed air has been proved beyond a doubt' at Port Chalmette. The con- 
clusion that the work is done cheaper by electricity is not warranted by the 
facts presented. It may be correct, but we want more evidence, 

"For instance, the statement that the cost of maintaining track under the 
compressed air haulage is much greater than under electric haulage is, we sus- 
pect, theoretical. An experience of about a year with one and half a year with 
the other, on new track, is not enough to justify so broad a conclusion. If all 
the details of expenditures on maintenance of track and machinery, of interest 
on cost of machinery, of fuel and wages account, and of work done, could be 
gathered, analyzed and compared, the result would be instructive and highly in- 
teresting. Until we see such details, however, we suspend judgment on com 
parative economy. 

"Concerning the experience with the compressed air plant, we have some 
information from another source. The first two air locomotives were furnished 
by Messrs. H. K. Porter & Co., and were shipped in October, 1895. A third, with 
greater tank capacity, was shipped in August, 1896. The compressor was fur- 
nished by the Norwalk Iron Works. The pipe line was bought and laid by the 



USE. 529 

railroad Qompany, and we understand that the builders of the motors and com 
pressor had nothing to do with the plan of the installation, the capacity of the 
piping or the arrangements for storing and charging. 

"Obviously, there were a number of things to be co-ordinated to get good 
results. The work of the motors in speed, frequency and loads, the capacity of 
the compressor, the storage capacity of the pipes, and the points of re-charging 
should all have been considered. , With the work in sight at the outset the first 
plans were probably good enough. Each motor was expected to make a round 
trip every half hour and to re-charge directly at the compressor ; there were two 
motors and they charged to a pressure of 600 lbs. per square inch. But the ton 
nage to be handled quickly developed so as to require three motors, making more 
frequent trips. For prompt, efficient and economical service there should have 
been storage capacity enough to equalize the pressure in the motor tanks in 
stantly, or practically so, when connected with the pipe line. There should have 
been pipes and connections so distributed about the yards and warehouses as to 
minimize the unprofitable engine mileage in running to and from the chargin;< 
places. The compressor should have had ample capacity for its work. The fact 
is that the only provision made for storing air was 1,542 feet of 5-incIi pipe, 
which gave less than one-quarter the volume of storage capacity necessary to get 
prompt equalization in the motor tanks. Most of the charging had to be done 
direct at the compressor, which took anywhere from 12 to 18 minutes, and the 
compressor did not have capacity to supply air to the three motors at the in 
tervals required. 

"It is not surprising, therefore, that the compressed air hauling was un- 
satisfactory, or that, as we have been told, the motors 'lay down out in the field * 
It would not be surprising, further, to learn that the hauling under these cir- 
cumstances was costly. Engine crews lost time while running to and from the 
charging station and while charging from the compressor, and the engines made 
a heavy percentage of empty mileage. Under all these contrary conditions it 
would have been surprising if the compressed air hauling had not been ex- 
pensive. 

"On the other hand, the former Chief Engineer and General Manager, 
who planned the work and started the compressed air haulage, writing to Com- 
pressed Air, says : 'During my management these pneumatic locomotives gave 
entire and complete satisfaction. These electric motors have about one-third of 
the hauling capacity of the pneumatic locomotives, are more expensive on ac- 
count of the fuel consumed, and have the ever-present danger of sparks in a 
cotton yard.' 

"But the difficulties and inefficiences developed later with the compressed 
air haulage have nothing whatever to do with compressed air. They, or others 
quite as great, would arise with any other system as inadequately planned. We 
do not understand that the Chief Engineer and General Manager, under whose 
direction the original air plant was installed, is responsible for its inadequacy. 
We judge that came about chiefly because there was more work to do than had 
been anticipated. On the whole, from such information as reaches us, this can- 
not be looked upon as in any way a satisfactory or conclusive lest of the relative 
economy and efficiency of hauling by compressed air and by electricity. 



530 USE. 

"There is still another consideration which we have never seen satisfac- 
torily dealt with. This place happens to be one where the fire risk is especially 
great. The principal business is hauling cotton, and the decks on the wharves 
and like places are covered with lint. One would say that an electric motor 
would be considerably more dangerous than a steam locomotive in such a place. 
Great care must be taken to prevent sparking, and the danger of starting fires 
by sparks must be constantly great. We have b^en told that the contract with the 
electric company requires that there shall be no sparking, and that all rails shall 
be kept clean at all times, which seems rather a hard condition to carry out. We 
have indirect information that the motors have really started several fires. On 
the other hand, our correspondent, who is and has been on the ground in a re- 
sponsible position, says that there have been no fires attributable to the electric 
motors. To his testimony, being direct and positive, we must give great weight, 
but we should say that the immunity must have been secured at great cost in care 
and vigilance, and we should be very apprehensive of the result if the electr^'c 
plant were under a management less skillful and faithful." 



A NEW GAS-PRESSURE GENERATOR. 



FOR INCREASING THE EFFICIENCY OF COMPRESSED AIR FOR TRACTION PURPOSES. 



The invention relates especially to pressure generators of the continuous- 
combustion type, whereby a greater amount of heat is saved and converted into 
a useful working pressure than has hitherto been possible. 

The objects in view are to provide a simple and instantaneous internal- 
combustion pressure generator where gas or oil vapors or other like rapid com- 
bustibles are burned in the retort or combustion chamber with the proper amount 
of air to form perfect combustion. The burned gases thus formed pass out of 
the combustion chamber, where they unite or commingle with steam that has 
been generated in the coils that surround the inner walls of the combustion 
chamber and pass from the combination to the mixing chamber. The steam 
issues from said pipes as "saturated" steam and, commingling with the burned 
gases, forms "superheated" steam, which is used expansively or otherwise in any 
desirable form of engine, whether it be a reciprocating, oscillating, rotary or 
steam turbine, but preferably in the latter. 

A further object of the invention is to provide an elastic motive fluid 
having the advantage of both gas and hot air and also steam without their dis- 
advantages—namely, the tendency which gas and hot air have to destroy the 
sensitive parts of an engine and also the rapid falling off of the pressure— since 
by the addition of steam the expansive qualities are prolonged and act more as a 
lubricant than as a destroyer of the lubricating agent. 

I is the combustion chanjber, having an opening or neck 2, leading 
into the mixing chamber 3, both forming compartments within the interior of a 
proper casing A. Through the bottom of the combustion chamber passes an in- 
duction pipe 4 and is made to form a coil and lining B for the retort or com- 



USE. 



531 



bustion chamber, leaving an opening at the center of the coil for the injection 
pipe 5 to pass through. Then this pipe 4 continues coiling around the inner walls 
of said chamber until it reaches the crown sheet C, where it also lines the same by 
being properly coiled, leaving an aperture in the center thereof, so as to not ob- 
struct the passage 2. From thence said pipe 4, after lining all the inner walls 
or surfaces of the combustion chamber, continues to make a series of flat coils 
6, that are suspended within the upper portion of the chamber i, and finally said 
coils end by turning up and passing through the central passage of the flat coils 
6 and through the neck 2 into the lower end of the mixing chamber 3, being held 
in position by a suitable bracket 7, through which it passes, and is secured by a 
nut 8. The bottom of the mixing chamber 3 is made within a convex head, con- 
sisting of the crown sheet C, in order that the water of condensation may be 
drained therefrom by the cock 9. The object of providing the two chambers i 




/a 



f^^E^' Comprgsscd aTi* 



FIG. 177 — MOTOR CAR WITH GENERATOR IN POSITION. 



and 3 with a flared-neck tube between them is to keep the combustion chamber 
I clear of any steam or moisture, so that only pure air is present to form perfect 
combustion in combination with the gas or oil vapors. After the products of 
combustion have passed through the neck 2 into the mixing chamber 3 and have 
commingled with the steam issuing through the nozzle 10, they then pass out 
through the eduction pipe 11 to the motor or other suitable point. 

Fig. 177 is a sectional view of a motor car, showing the generator in posi- 
. tion. 

The mode of operating cars that have a central station where air and gas 
are compressed and then delivered to the individual cars as they come in to be 
recharged, is as follows: 

First recharge the air and gas tanks under seats of cars. Then to start 
cars pull lever i forward gradually, thus opening simultaneously the gas valve 



532 



USE. 



3, the air valve 4 and the throttle valve 5. Valves 3 and 4 receive air and gas in 
proper proportion from their respective tanks through the pressure reducing 
valves 6 and 7, through independent pipes, until they reach the burner 8, where 
they unite and are fired by an electric spark between electric electrodes 9 and 10. 
and produced by pressing the push buttom 2 with the thumb, at the same time the 
lever i is pushed forward. At the instant the motor starts it pumps water auto- 
matically to the steam generating coils located in the combustion chamber of the 
generator. Thus the working fluid passes out of the generator through throttle 
5 to the motor and starts cars. 

When it is desired to stop cars, push hand lever i backward; this action 





FIG. 178 — REAR END VIEW OF HORSELESS CARRIAGE. 

closes all three valves, viz., air, gas and throttle, at same time cutting off work- 
ing fluid supply, thus stopping motor. 

Fig. 178 is a sectional view of the rear end of a horseless carriage, showing 
the generator and motor in position. 

In this instance it will be seen that the compressing station is dispensed 
with. As the plant is "self-contained," the motor doing its own compressing of 
air and delivering same to a supply tank on board. Said supply air tank is con- 
nected by a by-pass to the oil tank (kerosene or gasoline), in order to have the 
same pressure on top of the oil in oil tank as there is in the air tank, thus feeding 
the air and oil in proper proportion to th^ burner at equal pressures. 

^ The oil is first converted into a "fixed gas," "before" it commingles with 
the air, by a new gas generating burner (not shown here), also invented by Mr. 
Woillard recently. 






USE. 533 

The inventor of the above system is endeavoring to secure financial aid 
to put his invention upon the market. 

Interested parties can learn more by addressing the inventor himself. 



. MINE HAULAGE. 



Mr. E. P. Lord, Superintendent of H. K. Porter & Co., Pittsburg, Pa., in 
a paper read before a recent meeting of the Coal Operators' Association, review- 
ing the progress of compressed air, and particularly of mechanical haulage by 
compressed air, says : 

"Mining has been one of the most active means of giving prominence to 
compressed air. In these days of active competition and imperative demand for 
decreased cost of production, greater economies and improved appliances for 
cheapening the mining of coal have been absolutely essential to profitable mining. 
New fields, as soon as developed, have felt at once the necessity of installing the 
most approved machinery for mining, pumping and haulage; in fact, these im- 
provements have been imperative to keep in business. The mule, which has so 
long been used for hauling, has been very generally supplanted by more powerful 
agents, steam, electricity and compressed air. It is to the latter power as ap- 
plied to the motor for haulage purposes that I intend to principally confine my 
remarks. 

"In much work — in mine tunnels, confined spaces, etc., compressed air 
has fully demonstrated its superiority over steam or any other power. The work 
accomplished with it in your own Jeddo Tunnel, at Hazelton, needs no reference 
to here. Early uses of compressed air hardly presaged the wonderful develop- 
ment and application of this power to-day. For mine haulage it is very largely 
supplanting the steam locomotive, with its attendant disadvantages, and now 
electricity is about its only competitor. Until this competition manifested itself, 
air was generally considered a very undesirable power at best, and in many instal- 
lations, more particularly haulage, it was not thought of. I do not wish to be 
construed as saying that electricity and compressed air do not very frequently 
work in mutual harmony. Each has its own field of work, for which it is singu- 
larly fitted, and where no question of competition can arise. 

"Electricity can be used in most cases quite successfully for haulage. It 
can also be used for pumping, and made a success as far as operation is con- 
cerned, but in many cases at a large excess of cost over compressed air. But 
when you come to cut coal with electricity, many operators claim that no such 
results can be obtained as with compressed air, to say nothing about the increased 
cost of installation and subsequent operation. I have found it extremely difficult 
to get any statements from those using electricity for coal cutting, and there is 
no doubt or question but that there are some veins of coal which cannot be cut 
with the type of machine which is driven with electricity that could be success- 
fully cut with what is called the punching or pick machine. Where compressed 
air is superior for transmitting power for coal cutting and pumping, is it not rea- 
sonable to conclude that a good deal of consideration should be given to it for 
haulage ? 



534 USE. 

"Most of our engineers frankly admit that the electric motor is not an eco- 
nomical machine where the use of power is to be variable and intermittent, it be- 
ing essentially a constant speed machine. If we so block an electric motor that 
it cannot mdve, a considerable current of electricity will run through, without 
doing any work ; while a compressed air engine wastes no air or energy in start- 
ing, for air only escapes with piston movement. 

"The average mine engineer will usually show the liveliest interest when 
approached on the subject of an air haulage plant; but when he is called upon 
to choose between air and its very universal and most elaborately advertised 
competitor, electricity, no doubt he feels that the best known and understood 
agent is the best and safest in his case, although the compressed air plant, if suc- 
cessfully installed and started, might prove the most economical to his company. 

"I am pleased to state that in the introduction of our motor we have found 
in the anthracite district the most exacting, but at the same time, most tolerant 
listeners to our claims for recognition ; and the reports which have, and are now, 
reaching us from plants already installed among the operators of your region 
lead us to hope for, and promise even greater achievements in the advancement 
of this simple but all-powerful agent, compressed air. 

"The last few years have witnessed a very remarkable development of com- 
pressors and compressed air apparatus, due, no doubt, quite largely to the active 
competition of electricity in the many fields where this power is used. The great 
improvement made in compressors, together with reduced cost, have led to their 
more extensive adoption and the enlargement of their uses. In all respects its 
progress has fully kept pace with that of electricity. The compressor people are 
now called upon to design and construct machines to develop heat and produce 
cold; to move air with a force only sufficient to press gold into a sensitive tooth, 
and to blow the shot from a cannon. There is hardly a department of any large 
shop or manufactory that cannot testify to the remarkable economies that this 
power, ingeniously applied to various machines, has established. There are not 
less than 200 distinct and established uses of compressed air — to 90 per cent, of 
which electricity is inapplicable; and in the remaining 10 per cent., constituting 
the field open more or less to the other agencies besides air and electricity, we find 
air generally has the advantage. Except within the last few years, compressed 
air catalogues have been almost the only literature on this very important subject, 
while to-day we can hardly pick up an engineering paper without running across 
some article, paper or special mention of the great benefits that this new power is 
establishing for its recognition in the mechanical world. 

"Comparison with Other Power Agencies.— Compressed air has marked 
advantages over any other class of haulage, in that it is free to 'go wherever 
there is a track laid; the distance run with one charge of air is only limited by 
the capacity of the motor tanks. Great advancement has been made in the im- 
provements of compressors, pipe lines, pipe connections, motors, methods of 
charging, etc. ; so that for efficiency it is admitted that compressed air runs elec- 
tricity very close for a long-distance transmission. It is equally efficient and safe 
in fiery and non-fiery mines, and materially assists ventilation by the air given out 
by the exhaust. Too much stress must not be laid on this, for efficient ventilation 
must be provided for in any case; but compressed air is now used for driving 
mining machines in rooms or in butt entries, ahead of the general work and 



USE. 



535 



beyond the range of general ventilation. It not only supplies the necessary power, 
but furnishes an ample amount of fresh air, thereby materially reducing the risk 
to life and property. In the butt entries and rooms where ventilation has been 
difficult, and where, on account of low roofs, light rail, etc., other classes of 
power have not been introduced, the compressed air locomotive has been installed 
with very manifest success." 



HOPCRAFT'S PNEUMATIC RAILWAY. 

We give on these pages two views of a working model railway, about one- 
tenth of a mile long, which we recently had an opportunity of inspecting under 




FIG. I7HA — A MODEL i'NEUMATlC RAILWAY. 



working conditions. The system is one of pneumatic direct propulsion, involving 
the use of no motive mechanism on the vehicle. Between the ordinary rails, and 
supported by the sleepers, is fixed a supplementary rail of timber. On this rail 
i:> the motor tube, which, in its normal position, i. c, flat, appears as a narrow 
stretch of heavy canvas tubing. Within this tube, and effectually protected by it, 
is what would appear as a strip of india-rubber, in reality a tube, but so mounted 
on a flat wooden core that either side represents a firm, even surface. This motor 



536 



USE. 



tube is firmly attached by side fillets of wrought iron to the centre wooden rail. 
To utilize the power which air under pressure, when admitted to this tube, is 
capable of exerting, a rubber-tired wheel, wider than the motor tube, revolves 
freely on its axle, which is attacned to the centre of the car, midway between the 
ordinary wheels. This wheel, by means of a lever in connection with the axle, 
can be raised from or lowered on to the tube at will, and in conjunction with the 
brakes is worked by the conductor in charge, who thus has full control of the 
car. By depressing the wheel on-to the deflated surface of the tube, an air-tight 
joint is formed, and on air under pressure being admitted to the tube, on the side 




FIG. 179 — A MODEL PNEUMATIC RAILWAY. 

opposite to that in which the carriage has to travel, inflation takes place, and thus 
a powerful propelling force is exerted against the wheel, causing the car to travel 
at a speed practically limited only by the speed of the air in the tube. 

In the model illustrated, the motive fluid is carbonic acid gas, stored in 
flasks in highly compressed state, but reduced before it is admitted into the motor 
tube to a pressure of about 8 lbs. per square inch. This gas has been employed 
in order to dispense with an engine and compressor. The guage of the railway 
is two feet, and the weight of the truck in working order is about half a ton. The 
line is a dead level for about three-fifths of its length, when it has a slight fall 
and then a rise. But at the further end is a short length, with a gradient of about 



iMi 



^y^^- 



USE. 



537 



I in 6, which has been constructed to show the capability of the system for work- 
ing up an incline. This is shown in one of the illustrations. With a pressure of 
about 8 lb. in the tube the car could be easily started up this incline. Numerous 
applications of this system of propulsion suggest themselves ; for instance, quick, 
light railways for exhibition purposes, or for the transport of goods in ware- 
houses and factories. The inventor is Mr. L. Hopcraft, of Kelvedon Common. 
Brentwood, Essex. — The Engineer. 



THE BROADWAY TUNNEL. 



In December last a fire which destroyed the building occupied by Rogers, 
Peet & Company, corner Broadway and Warren streets. New York, disclosed the 
famous Beach Broadway Tunnel, which was built thirty years ago for rapid 




FIG. l80 — PNEUMATIC CAR IN THE BROADWAY TUNNEL. 



transit purposes. It was proposed that compressed air should be used to drive 
cars through this tunnel. In the Spring of 1870 the tunnel was opened for 
inspection to the public and crowds of visitors enjoyed a walk through it — many 
people enjoyed rides through the tunnel in the car which was driven by pneumatic 
power. The remains of the car are still to be seen. It is elliptical in shape and 
practically filled the entire tunnel. In City Hall Park, where the tunnel termi- 
nates, an air well served as an outlet and inlet for air according as the car was 
driven by pressure of air on its end down the tunnel from the huge blower or 
driven back to the place of starting by the suction of air in a reversed direction. 
Horace Greeley and other distinguished persons took rides in this car. 



538 



USE. 



LONDON'S LOST TUNNEL. 

Is there any other city in the wide world where a cast iron tunnel, two and 
three-quarter miles in length, could lie disused, unknown, lost to the memory 
of all but a few scientists, for over thirty years, excepting London? I doubt it. 
For this commercial hub of the universe spins onward at such a rapid rate, that 
the doings of yesterday are already shrouded in mist, and those of a decade back 
buried as deeply as if the dust of centuries, not years, lay upon them. 

So it is that, under the hurrying feet of millions, even echoing their tramp 
through the heart of the great city, for long years has lain this almost imperish- 
able testimony to the enterprise, courage, and, alas! misjudgment, of certain of its 
citizens of the "Sixties." Expert engineers have examined the tunnel and pro- 




ne. 181 — PNEUMATIC ENGINES, HOLBORN STATION. 



claimed it to be composed of the very best metal — "cast iron such as is not turned 
out to-day," to quote the words of a prominent expert — and but little affected by 
earth, moisture, or disuse, for all its lengthy interment and neglect. Representing 
as it does the burial of close on £200,000, is it not simply marvellous that no effort 
until the present has been made to rescue this valuable property from the fungi 
and huge, whiskered rats, and turn it to some profitable utility? The answer is 
that the tunnel had been forgotten, simple lost, and the man who "found" it found 
a gold mine extending from the G. P. O. at St. Martin's-le-Grand to Euston Sta- 
tion. Should the sanguine hopes of the discoverer be realized — and they are based 
on the reports of the leading authorities— he has "struck" a payable "lead" that is 
not likely to be "worked out" until flying machines are as ubiquitous and numer- 
ous as hansoms in London streets. 



w 



USE. 



539 



Mr. George Threlfall, a consulting engineer, of 50 Fenchurch street, "found" 
the tunnel, and the story of his discovery is one of surmounting an almost inter- 
minable Alps-of-obstacles, and a period of five years occupied with continual 
struggle before success crowned his efforts. 

The memorable year of 1863 welcomed the abolition of slavery in America, 
shuddered at the fierce fighting of kin against kin in the Battle of Gettysburg, 
grieved at the deathbeds of three memorable men — Thackeray, Stonewall Jackson 
and General Sir James Outram — and showered sunshine and good wishes on the 
marriage of H. R, H. the Prince of Wales. It saw also the opening of the Pneu- 
matic Dispatch Company's first section of the tube that, later, starting from 
Eversholt P. O., N. W., passed down Seymour street under the Euston Station, 




FIG. 182 — TRAIN OF CARS, HOLBORN STATION. 



along Drummond street, turning into Hampstead Road, and continuing the length 
of Tottenham Court Road until New Oxford street was reached, under which it 
ran, and under Holborn, plunging deeply down the Viaduct, passing below Far- 
ringdon street, shooting up into Newgate street, and finally reaching home in 
the old G. P. O. buildings on the corner nearer Cheapside. The tube, which 
measures four feet in height by four and a half in width, was erected to carry the 
mails and postal parcels between the two terminal points and wayside offices by 
means of pneumatic pressure. 

A lad with a pea shooter utilizes pneumatic pressure in propelling his sting- 
ing pellets by introducing a force of air behind them ; in an inverse manner liquids 
are imbibed through a straw by sucking the air out, when the interior liquid, thus 
relieved from pressure, is forced by the weight of the atmosphere on the outside 
liquid up through the straw. Both these forms of pneumatic pressure were 



540 



USE. 



utilized to drive the loaded cars of the Dispatch Company through the tunnel 
The car ends fitted the tunnel to within an inch all round. The intervening space 
was closed so as to be perfectly airtight by a flange of stout indiarubber, which 
clung tightly to the tube's interior. The air was sucked out from in front of a 
train of cars by an ingenious mechanical arrangement. Two discs of wrought 
iron, twenty-one feet in diameter, were screwed on to the sides of an iron wheel 
having sixteen spokes. Between these two discs, and separated from them, stood 
a third disc of a corresponding size. Thus this cumbersome wheel, complete, con- 
tained thirty-two V-shaped cavities. Briefly, it may be said that the revolution 
of these cavities at a great speed, before huge bell-mouthed pipes, drew by cen- 




FIG. 183 — EXPERIMENTING AT BATTERSEA, 



trifugal force the air out of the tunnel along which the cars, drawn by suction, 
sped at a rate of thirty-five miles per hour. 

The tunnel as it stands to-day is made up of cast iron sections in nine feet 
lengths and nearly an inch in thickness. Each section was cast in one piece, and 
in shape resembles a "D" lying on its back, with a groove in the corners along 
which the rails are laid. At the stations hermetically sealed spring doors excluded 
the entrance of air, so that when necessary a vacuum could be produced before the 
departing cars. The addition of an engine to revolve the hollow wheel I have 
described completed the whole outfit of a scheme that was to revolutionize the 
prevailing forms of carriage and general motion. In a Times leader of February 
loth, 1863, I have found the following: "Between the pneumatic despatch and the 
subterranean railway the days ought to be fast approaching when the ponderous 
goods vans which now ply between station and station shall disappear forever 
from the streets of London." Over thirty-six years have passed, and the railway 



USE. 541 

an is to-day more ponderous, ten times more numerous, and a hundred times 
greater danger to those who use the streets. And yet we boast of our progress ! 
Nevertheless, the journalists of those days revelled in dreams of pneumatic enthu- 
lasm; and schemes, that doubtless then appeared well controlled and feasible, 
0-day are known to have been of the wildest and most improbable. Listen to the 
exultation-cum-wailing of the Seven Days' Journal, apropos of the Pneumatic 
Dispatch Company under date December 13th, 1862 : "We are fast making Lon- 
don a marvellous and unequalled city ; and if with all our improvements and 
inventions we could only devise some means for rendering the three millions of 
Iwellers in it safe from the murderous attacks of garotters and burglars, we 
ihould have just reason to be proud of our smoke-covered, but unmatched, 
capital." Well, the smoke is still with us in greater volume than of old; but the 
many-tailed cat has tamed the murderous thief, and the Pneumatic Dispatch Com- 
pany has been resurrected and is promised a new life, with electricity for its vital 
power. 

Yet another reference to "olden times," and the dead past must give way 
to the living present. The London Journal, in 1863, printed this piquant para- 
graph : "Not only have letters and parcels been transmitted through the tube, but 
we hear also that a lady, whose courage or rashness — we know not which to call it 
— astonished all spectators, was actually shot the whole length of the tube, crinoline 
and all, without injury to person or petticoat." Following on this came a multi- 
tude of proposals for pneumatic passenger traction. A trial railway was laid at 
the Crystal Palace, and proved successful. The Waterloo to Whitehall Pneumatic 
Railway Company was formed. Great Scotland Yard was fixed upon as a site for 
one terminal station, and adjoining the Waterloo Station in York Road the other. 
Excavating and tunnelling were commenced. The river was to be crossed in an 
iron tunnel resting in a dredged channel across its bed. The Illustrated Times of 
August 17th, 1862, gave a full-sized plate, showing the works in progress, and in 
accompanying letterpress claimed that, "in its present form, the pneumatic system 
is simply an adaptation of the process of sailing to railways, the wind being pro- 
duced by steam power and confined within the limits of a tube." Passengers were 
to have perfect ventilation, no smoke (excepting tobacco), no steam, no jolting, 
no vibration, no collisions, and, in fact, none of the disadvantages more or less 
attendant on any railway line in the kingdom to-day. Although Messrs. T. 
Brassey & Co. were the contractors for this ideally perfect railway line, I cannot 
say where it has disappeared to. Evidently it savored too much of Elysium to be 
allowed to remain on earthly shores. 

Many persons, however, made the journey in the Pneumatic Dispatch Com- 
pany's cars. The Evening Standard of April 5th, 1863, mentions "Prince Na- 
poleon and his secretary" as being among the passengers, and an illustration on 
page 623 shows the Holborn Station — which was located in close proximity to 
the present Royal Music Hall — with a departing car passenger-loaded. For this 
plate I am indebted to Mr. T. E. Gatehouse, responsible editor of the Electrical 
Revieiv, Fellow of the Royal Society, Edinburg, a member of the various Institu- 
tions of Engineers, Civil, Mechanical and Electrical, besides being a well-known 
amateur violinist. Mr. Gatehouse entered the service of the Pneumatic Dispatch 
Company in 1869 — in days of his fallow youth — and scores of times made the 
journey through the tube, lying in the fast-flying cars. "The central station was 



542 



USE. 



in High Holborn," he states, "and contained the whole of the motive power. 
Here the cars changed from one set of rails to another, and the time taken in 
completing the whole journey from end to end was nine minutes. It was 
always an exhilarating journey, the air being fresh and cool even on the hottest 
summer days. From Holborn Circus, where the tube dives down a steep declivity 
under Farringdon street, the speed wa.s about sixty miles an hour, and in the 
vlarkness it felt as if I were sliding down a hill feet foremost. The impetus of this 
rush would carry the car up the incline to Newgate street. To me, who made the 
trip for the first time, there was something weird and uncanny in being shot 
through a tube at a high rate of speed, so near the surface of the roadway that the 
clatter of hoofs and the rumble of vehicles could be distinctly heard, accentuated 
frequently by the tallow candle or oil lamp being extinguished by the draught. I 




FIG. 184 — PNEUMATIC DISPATCH EXPERIMENTAL WORKS AT BATTERSEA. SHOWING 
PNEUMATIC DISC AND ENGINE. 



got SO accustomed to the journey that I could tell what corner I was turning, and 
the street above, precisely, at any moment." 

After a period of eight or ten years, the Pneumatic Dispatch Company 
relinquished operations. At intermittent times only had the line been worked; 
and quietly, without fuss or flurry, as became the collapse of a gigantic scheme, 
the end came, and pneumatic propulsion on a wholesale scale received its death- 
blow in the minds of experts. The insuperable difficulty lay apparently in the 
impossibility of rendering the tunnel sufficiently air-tight. Leakages of various 
extents prohibited the creating of a working vacuum, and after the engine power 
had been increased until it attained six times its original strength, further efforts 
were considered useless. 

The Company had been an extremely powerful one, with rights and priv- 
ileges guaranteed to it by special Acts of Parliament. Among the directors were 



USE. 543 

the Marquis of Chandos, the Hon. W. Napier, Sir Charles J. H. Rich, Bart., 
Messrs. W. H. Smith, Thomas Brassey, and others. Mr. John Aird was the con- 
tractor of the line, of which Messrs. T. W. Rammell and J. Latimer Clarke were 
the joint engineers. 

It was in 1895 that Mr. Threlfall first entered the disused tunnel, after 
struggling and squirming through a heap of debris and lumber in a basement of 
Euston station, alongside Seymour street. For many yards from the entrance 
of this terminal there was a trough to allow of the air propelling a car to escape 
and thus reduce the impact on the receiving buffers. An incautious step upon the 
rotten wooden platform here precipitated the unwary explorer into three feet 
of stagnant water, but he nevertheless kept his ardor dry, and after several weeks 
practicably completed his inspection of the whole tunnel (excluding the portion 
below Holborn Viaduct, which he found full of water), and decided that a fair 
expenditure would put it in working order for the propelling of cars by electricity. 

Having discovered the tunnel and realized its effectiveness, the still more 
difficult duty devolved on Mr. Threlfall of finding its owners, the original share- 
holders, or their heirs, together with the necessary plans and papers. It was 
indeed strange that the mouth-open tunnel, separated from a busy street by merely 
an iron railing and a few steps, should remain undiscovered even by those of our 
community whose misdeeds or intentions force them to hide from the inquisitive 
glare of X 2671's bull's-eye lantern and the clink of his handcuffs. In the 
troublous times of 1883-84, when misguided wretches were attacking with dyna- 
mite bombs London's main thoroughfares and buildings, one shudders to think 
what the knowledge of the tunnel's existence might have led to on the part of 
these miscreants. Some dynamite, a line of wire, and a battery spark, and the 
Nihilist, Anarchist, or Fenian might have sat in safety and ripped a track of death 
and desolation throughout the metropolis. But there are no apparent signs that 
the tube was ever the hiding place of any human being. Merely a few skeletons 
of rats, and presumably cats, judging by the size — what a Homeric combat of 
"fighting against odds" do these crumbling bones suggest! — and here and there 
umbrella-shaped fungi where the water condensation is greatest. 

Stranger almost than the loss of the tunnel was the disappearance of its 
owners and the papers that would tell who they were. After eighteen months' 
hard search in government offices and the five parishes through which the tube 
runs, Mr. Threlfall realized that neither they nor the original contractors had a 
single plan of the route. It was not until after a wearying system of inquiries half 
over England and on the Continent that Mrs. Frances Rammell, the widow of the 
late T. W. Rammell, a famous engineer, was discovered, and, through her 
remarkable energy, the original plans were eventually brought to light. 

To realize the commercial value of the tunnel's discovery and rehabilitation 
it is necessary to have some slight idea of the extent of mails and parcels passing 
not only between Euston and the G. P. O., but also between Eversholt P. O., the 
other local offices en route, and the two main termini. Practically all the heavy 
post to the north of Great Britain passes through the Euston Station, and the 
heaviest hour of the day sees a total of eleven tons of postal matter leave the G. 
P. O. for the Northwestern Central Station. At present, vans carrying from one 
and a half to two tons each, and taking twenty-four minutes under the most favor- 
able circumstances, njake the connecting journey. Heavy traffic, fog, greasy 



544 USE. 

pavements, or other drawbacks to vehicular motion, may double the time occupied. 
The contract time for the delivery of the mails to the various stations is eight 
miles an hour, and the enforcement of this rate of speed is one of the G. P. O.'s 
chief difficulties. For a time motor-cars were tried, but without success. The 
road to Euston is perhaps the most difficult of all to make progress along, and 
there is no doubt the tunnel, when fitted, will be an enormous convenience to the 
postal authorities. 



COMPRESSED AIR APPlTeD TO TRAVELING MOTORS BY A NEW 

METHOD. 

While compressed air has shown itself a successful rival of electricity in a 
variety of problems in power transmission, in cases where motive power is to be 
supplied to traveling motors, the latter has heretofore completely distanced its 
rival. The great difficulty encountered in using compressed air for this purpose is 
that the air is necessarily carried on the inside of the pipe, and is therefore inac- 




cessible except at the ends or outlets of the latter, while the electric conductor car- 
ries its fluid on its surface, from which the current can be taken at any point along 
its whole length. This has been an insuperable objection to the use of com- 
pressed air at a moderate pressure as a motive power where the motor travels 
great distances, as in the case of street cars or other traction. The result has been 
that while electricity has been applied to this use in a way most favorable to 
economical results, the advocates of compressed air have been obliged to resort 
to high pressure reservoirs carried on the cars, greatly increasing the cost of 
power plants, occasioning delay in recharging and a great sacrifice in economy 
due to the extremely high pressures required. 

In such an unequal contest it is not surprising that electricity has been the 
victor. 

Even in cases where the motor is only required to travel over a limited 
space, as in traveling cranes and overhead hoists, although compressed air is suc- 
cessfully used, the customary arrangement of flexible hose, supported by car- 
riages, is at best crude and objectionable, occupying as it does much valuable 
space and in consequence limiting the travel of the motor to a portion of the 
working space. 



USE. 



545 



The object of this article is to call attention to a recently invented method 
of applying compressed air to moving motors, which will obviate these difficulties, 
and will, it is confidently believed, place compressed air in a position to com- 
pete with its rival under similar conditions. 

This method is exactly analogous to the "trolley system" for electricity; 
i. e., the line of travel and is drawn thence by the air is carried in conduits 
parallel to the motor, as required, continuously along the whole length of the 
line. The device by means of which this is accomplished was designed primarily 
with a view to its application to street car service, as the cuts indicate, but the 
principle may be equally as advantageously applied to traveling cranes and other 
motors of limited travel. In fact, after a description of the device, as applied in 
street railways, it will readily be seen, without any further explanation, how 
various other applications can be made. 

The figures show the arrangement for a double track road. A (Fig. 185) 
represents the main conduit or supply pipe, which is laid between the two tracks 
and supplies air under pressure to cars on both tracks, and its size and conse- 




FIG. 186. 



quent construction is, of course, to be determined by the requirements of each 
case, and depends upon the pressure carried, the number of cars, and the length 
of the line. 

This air main is connected at intervals of about 6 feet with the auxiliary 
main B (Fig. 185) laid in the center of each track, by means of the pipe C. 

These auxiliary mains are made of cast iron, and are rectangular boxes 
about 6 feet in length, and of the section shown in Figs. 185 and 187 being entirely 
closed, except for a slot C, formed in the top the entire length of the casting, 
into which is fitted a strip of rubber D (Fig. 187), the latter serving as a valve, 
and having inserted in it at intervals stiffening pieces E of iron, which render the 
valve rigid transversely but flexible longitudinally. 

The strips D are bent downward at their ends, as indicated at D' (Fig. 187) 
and held fast at these points to the main D by a dove-tailed slot D^ and they are 
also provided with springs F, which insure their return to the seat after being 
opened in any part of their length, as will be more fully explained. 

Attached to the top of the main B are curbs G, of rolled steel, which form 
the slot at the surface of the street, and the mains and rails forming the tracks 
are shown resting on cast iron ties or foot blocks G\ although this const-ruction 
might be modified by using wooden cross ties and wooden string pieces to raise 
the rails to the required level. 



546 



USE. 



The trolley or connecting device consists of a brass box H sliding upon the 
upper surface of the main B and being where it comes in contact with the valve 
or the sides of the slot. 

The sliding surfaces are to be lubricated by means of oil cups carried on the 
trolley. 

The trolley box H is provided with a small wheel, or valve roll I, which 
rolls on the valve strip and presses it down immediately on coming in contact 
with it, as shown in Fig. i88, thus allowing the compressed air to pass into the box 
H. To the top of the latter is bolted a steel casting J, which is narrowed to pass 
through the slot and strengthened by ribs, as shown. It is also provided with 




'T ' JiiJ)^)^)^^^^^^ 



FIG. 187. 



FIG. 188. 



tie rods K to brace it longitudinally. The upper end of the casting J has an 
extension J\ which is threaded into the tube M, and resting on its upper flange 
y is a spring N, which may be adjusted by means of the screws p, which bear 
against the cap plate O and are threaded through the flange of the gland P. 

The object of this spring is to compensate for any irregularities in the track 
and at the same time to overcome the upward pressure at the lower end of the 
trolley, insuring the latter's remaining firmly on the main B. 

The gland P and the stuffing box Q, through which the tube M passes, 
are fastened to the frame of the car, and the stuffing box fits against a washer 
plate Q\ which is placed into position after the check-valve R and its seat-casing 
R\ which also serves as a collar on the tube M, have been placed in position. 

The air is led from the stuffing box Q by means of the short pipes Q^ to 
the reservoirs S, and these serve to equalize the pressure on the motor, and 
also act as a storage for a sufficient amount of air to start the car if it should be 



USE. 547 

stopped directly on the crossing or turnout, where the trolley would be momen- 
tarily disconnected from the supply main. 

The motor may be of any ordinary type, as determined by the conditions 
of the case. 

The advantages claimed for this method of street car propulsion are : 

First. Economy of first cost. 

While the first cost of such a road would be greater than an overhead 
tiolley line it would compare favorably with the underground trolley and be much 
Ifcss than a cable road, while the cost of power plants would be much less than 
for any of the other systems. All that would be required would be a battery of 
boilers and a series of steam-driven air compressors, which are much cheaper 
than either electric or cable machinery, and require less space and consequently 
less ground and cheaper buildings. 

Second. Economy of operating. 

As compared with the underground trolley system, the efficiency of the 
power plants should be about the same, each consisting essentially of a steam 
plant and a transformer. The efficiency of the line, however, would be greatly 
in favor of the compressed air system, owing to the leakage from the underground 
electric conductor, which it is extremely difficult to insulate, and the greater per- 
centage of energy used to overcome resistance in the latter. As the cable system 




FIG. 189. 

is now practically obsolete, it is useless to make any comparison with that, 
although the advantage would be still greater. 

Third. Miscellaneous advantages. 

Among these may be mentioned simplicity of machinery, as compared with 
any electric system, both in the power house or on the car, requiring less technical 
knowledge to operate or repair, less danger of breakage, in the first place, and 
less cost to repair when broken. This system also provides the means always at 
hand for an efficient and quick-acting brake, which is an appliance greatly pro- 
vided with a soft rubber packing H^ needed for street car service if high speed 
is to be attained. 

This device, as can be readily seen, can be easily applied to traveling cranes 
and similar machines, with a saving of space and convenience in operating, but it 
has another application in which it far surpasses any other system, viz. : Under- 
ground railways, because motors operating under this system not only would not 
vitiate the atmosphere of the tunnel, but would furnish a positive and costless 
method of ventilation by means of the exhaust, infusing fresh air at all points 
along the line, and just in the proportion required. This system could be applied 
to tunnels of existing railways, with the object of ventilation, by using the cylin- 
ders of the present locomotives as motors and applying the compressed air while 
in the tunnel by providing the apparatus with a mechanism for dropping it when 
Hearing the tunnel in a somewhat similar manner to that now employed for taking 



548 USE. 

water from track tanks. When the apparatus was dropped the steam would of 
course be shut ofif and the damper closed so as to prevent any smoke, steam or gas 
from escaping, and the air used as a motive power until the farther end of the 
tunnel was reached, when the apparatus could be raised and steam used again. 

This application could hardly be expected, however, to appeal very forcibly 
to railway management, as it would entail considerable expense without any 
immediate visible return, but the vast army of commuters who are compelled to 
pass twice daily through any of the tunnels leading out of New York, with cars 
crowded, a temperature of lOO F. inside, and all windows per force tightly closed, 
would shower blessings on the head of any one who would devise some means of 
relief. 

There are many other minor applications of this device, but the limits of 
this article preclude anything further at this time. Its object will be attained if it 
will convince some one of the value of this invention to the cause of compressed 

air. W. M. FARRAR. 



AIR HOISTS. 

Compressed air hoists for the purposes that they are designed for have 
made an enviable record in machine shops, foundries and other places where air 
is used. Lately we have heard numerous complaints about the service they give 
when they are indiscriminately applied to shop work. Some have gone to con- 
siderable trouble to make the hoist efficient for all purposes, without satisfactory 
results; one specific complaint being that air admitted to the hoist to suspend 
a weight at a fixed point for a considerable length of time, does not do it, as the 
air will leak and the weight will fall. The superintendent of a prominent manu- 
facturing firm writes Compressed Air as follows : 

"Our experience is that all hoists, as constructed at present, are more or 
less failures because of faulty valves, poor means of operating valves, and pistons 
mechanically improper for the service in which they are used. We have been a 
little unfortunate, probably, in our hoists, in the cylinders. They have been bad, 
and we have been able to repair some of them, but even after that we have not 
got to the seat of the trouble. We have tried leather pistons, three snap ring 
pistons, and hardwood ring pistons. The latter gives us the best satisfaction, 
yet none of them will sustain the heavy load for any protracted length of time. 
By that I mean for half an hour. This applies to vertical hoists only, as we do 
not use horizontal hoists. A hoist that will be simple and effective and which 
will obviate the difficuUies experienced by people who are using them, would be 
appreciated. 

"We have also had difficulty in obtaining a coupling on which the hoist 
will stay. We blow them off about twice a week." 

We will be glad to have the experience of others, and will publish sug- 
gestions that may be made bearing upon this subject. 



USE. 



549 



Compressed Air : 

The article on air hoists in the last number of Compressed Air may have 
created a wrong impression on the minds of a great many people who do not use 
air hoists. Those who use straight lifts know the disadvantages of them and 
the difhculties attending their use. They also know their good points and what a 
saving in time and labor they effect with them. The people who do not use 
air hoists may get the idea that there is no air hoist on the market that will hold 



FIG. 190. — RIDGWAY OIL CONTROLLED HOIST. 



a load absolutely and without qualification or do successfully any or all the 
work of hoisting or lowering loads that may be required of it. 

There is such an air hoist and we show a cut of it. This is the pneumatic 
motor hoist made by the Empire Engine and Motor Co. of 26 Cortlandt Street, 
New York City. 

This is a hoist that will do any of the work required of an air lift or elec- 
tric hoist and do it without the danger or difficulties attending their use for cer- 
tain classes of work. In the first place there is a great saving of head room as 
there is no cylinder used, consequently no thought has to be given to the hoist 
itself in regard to length of lift wanted. The length of chain is its only limit 



550 USE. 

of lifting. It will hoist accurately and steadily one quarter of an inch or twenty- 
five feet. . The method of operating is exceedingly simple : the operator having 
perfect control of the motor at points. One of the strongest points made in favor 
of this hoist is its power of absolutely holding any load up to its full capacity at 
any point of the lift. This point is made Without qualification, and the Com- 
pany guarantee it. It is so constructed that it does not depend on the air pres- 
sure at all to maintain the load. In fact, the motor may be detached from frame 
while load is suspended without affecting the load in the least. Then, too, in 
starting or stopping or in changing the weight of a load there is no vibration or 
jumping as in a cylinder lift, consequently no danger of blowing out cylinder 
heads or hose connections. 

When made of brass the tubing is taken just as it comes from the mill, 
and is neither round or smooth like a bored cast iron cylinder. So the piston 
must be made a very loose fit, or it will stick while the pliability of leather is 
depended upon for it to adjust itself to the inequalities and roughnesses of the 
bore. Such a hoist will leak more or less, of course, but for looks and work it 
will do fair service and it is cheap. 

When steel pipe is used it is bored out, but because it is only a little more 
tnan Ys inch thick, it is hard to keep it round, rarely is bored round, and when 
the weld is made, always shows up more or less seamy when bored. The 
leather cup as in the brass pipe is expected to be obliging, and so such hoists 
while they must leak, for lots of work, will pass muster, and they are cheap. 

Then to prevent these air hoists from becoming veritable air guns and 
shooting the piston through the roof or at least try to do it. When anything 
gees wrong, elaborate valves must be used. In a little while these valves get leaky 
of course, and the load won't stay where the owner wants it, and then goes up 
the plaintive cry we just now hear from your correspondent. 

An air hoist needs but one simple valve, and that a cock like you use on 
your gas fixture which runs for years without a smell, that is all and that is 
enough. To prevent jerkiness and running away when anything happens, such 
as the breaking of a chain or the careless throwing on a full head of air when 
there is no load, we submit our plan of oil governing by putting a quart or two 
of oil in the piston rod. This with our cast iron bored cylinders costs more than 
the pipe affairs and is worth more. Whether we can sell them depends ; to be 
determined by how sick people are of the other sort. We have just put it on the 
market. It is a magnificent tool, but you know how things are, the fellow who 
makes the cheapest thing that will pass muster knocks the persimmon. 

CRAIG RIDGWAY & SON. 

Engineers, Founders and Machinists. 



Editor Compressed Air: 

Dear Sir — Have been a reader of Compressed Air for over a year, and 
while I am very much interested in air power and hope to see its adoption in 
many places where it now is not, I am not in a position to put any of it to good 
use except in the way of keeping up a fresh supply for respiration purposes. 

At one time I was quite familiar with clearing up railroad wrecks and I 
remember the slow process of the hand derrick for hoisting and removing the 



USE. . 551 

debris. On a busy road where both main tracks are blocked, this always means 
a big delay. 

Some time ago I happened into the foundry of J. J. Radley & Company, 
New York, and found there a little motor of the reversible and direct-acting piston 
type attached to the gearing of an old-fashioned hand derrick and operated by 
compressed air for lifting heavy loads. This little motor easily lifts 8,000 pounds 
10 feet per minute, and by changes in the gearing can be made to lift almost any 
load. 

If this motor was attached to the derricks which are erected on wrecking 
cars, it would enable wrecking crews to clear up wrecks very much quicker than 
they do by hand, and 1 believe it would figure out a considerable saving per 
wreck. The whole expense of putting in the appliances would not exceed $200; 
that would buy the motor and an air receiver. Every engine pulling a wrecking 
car has an air brake pump and can supply sufficient air for all requirements. 
The receiver should be of good capacity so that rapid work could be done without 
danger of diminishing the air pressure at a time when most needed. The re- 
ceiver can be located on the derrick car or under it. From the time the engine 
is coupled to the wrecking train the work of compressing air may begin, and 
long before it reaches the wreck a good supply may be laid up. The intervals 
between each lift are usually long enough to allow the supply of air to be 
replenished. Should the air fail at any time, which is not probable, the derrick 
can be operated by hand as usual. It takes at least- four men and sometimes more 
to raise an ordinary coal "jimmy," and it takes several minutes to wind up by 
hand what can be done in a very few seconds by air. One man to handle the 
valve is all that is required, and the time saved in raising ten coal "jimmies" would 
be at least an hour. 

I believe some of the larger railroad systems have steam cranes for wreck- 
ing purposes, but I know there are many roads which still use only the hand 
derrick. The work of attaching these motors is not difficult, and to the master 
mechanics who read your interesting journal I submit my plan, if you will be 
kind enough to publish it. A subscriber. 

Harlem, Nov. 8th, 1898. 



AIR HOIST IN MINING OPERATIONS. 

The Mansfield Coppen Minin'g Co., in Germany, have installed a com- 
pressed air hoist in their mines, as it enables them to raise or transfer the cars 
from one track to another more expeditiously than heretofore possible by use of 
the hoisting screw. A compressed air cylinder is arranged upon a movable 
frame suspended at a height of 6 feet 8 inches. The frame can be moved on the 
rails with great ease, the air being supplied by an india rubber hose. The piston 
rod of the air cylinder is connected to a system of levers, which are arranged for 
the purpose, grabbing and lifting the wagon as soon as the air valve is opened. 
The releasing and lowering of the wagon is effected by opening the exhaust valve. 



552 



USE. 



AN AIR HOIST FOR MERCANTILE PURPOSES. 



Pedestrians who pass the store of the Nason Mfg. Co., 71 Beekman St., 
New York, are often puzzled by the ingenious method employed in unloading 




FIG. 191. — THE UPPER PART OF THE HOIST SHOWING TROLLEY AND HOSE. 




FIG. 192. — HOSE DRUM. 



boxes, barrels, radiators, bundles of pipe, crates of earthenware, boilers, ranges, 
furnaces and innumerable other heavy pieces, from the dray that stands in the 
street in front of the door. A crane is swung over the sidewalk, and it supports 
a hanging cylinder which has been conducted from the interior of the store upon 



USE. 



553 



the trolley rail of the crane. To the cylinder is attached a line of flexible rubber 
hose, which being supported on rollers having anti-friction bearers, leads to the 
rear of the store, where it winds or unwinds upon a metallic drum, as the trolley 
is pushed backward or forward upon its rail. Compressed air at from 65 to 75 lbs. 
pressure is supplied to the cylinder through the hose — it being taken in through a 
stuffing box at the centre of the drum. The air is stored in a suitable reservoir, 
into which it is pumped by a small compressor — the latter starting and stopping 
automatically by means of variation in the air pressure. 

When the cylinder reaches the proper point it hangs pendant over the load 
of merchandise; the driver of the dray opens a valve and thus admits the com- 
pressed air beneath a piston. A piston rod projects through a stuffing box on the 
under side of the cylinder, and being provided with a hook, clamps of varying 




FIG. 193. — UNLOADING MERCHANDISE IN STORE. 



patterns which are hung to it are attached to the article to be unloaded. The 
valve is closed and another one opened, when the load rises and is then readily 
pushed into the store and deposited in its proper place along the line under the 
track. 

The cylinder is the oft-described "air hoist," and this particular one, com- 
bined with the rest of the apparatus, is known as the "Nason Pneumatic Lift." It 
was designed and patented by Mr. Carleton W. Nason several years since, and has 
been in operation at the stores of the Nason Manufacturing Company for about 
three years, during which time not a cent has been expended for repairs of any 
sort. 

Fig. 191 shows a piece of the track with the trolley on it, and also the means 
of supporting the hose between the trolley and the revolving drum. This feature 
is both important and necessary, as it permits of an extension of the line up \o, 
say, 150 feet in length without undue friction. 



554 



USE. 



Fig. 192 shows the reel with the device for winding the hose upon its pitch 
line, which is accomplished, it will be noticed, by means of a pair of rolls fastened 
to a carriage which slides upon a lead screw— the latter being driven by a pair of 
sprocket wheels and chain belting — their dimensions being such that the central 
point between the rolls is always opposite the point on the drum upon which the 
hose is to be rolled. A weight suspended from a smaller drum, which is attached 
to a shaft common to both drums, takes up the slack of the hose between the rolls, 
and keeps it always under moderate tension. 

When our artist appeared upon the scene, a large 4 x 24 radiator was being 
taken off the dray and into the store. Its weight was about 600 pounds, which is 




FIG. 194. 

much within the capacity of the lift. The cylinder in use with this hoist being 
five inches in diameter, it gives a lifting capacity with the air pressure used of 
about 1,250 pounds. Other stores in the city are about to be equipped with the 
Nason Lift, and its use may extend to a long list of applications in commercial 
lines and wherever heavy articles are to be transferred. This hoist is particularly 
valuable in New York, Boston and other places where narrow streets abound. 
The load is discharged rapidly and relieves the blockade that so frequently occurs 
on these streets. Ships may be loaded and unloaded in the same manner. The 
time that may be saved in discharging cargoes would also play an important part 
in increasing the facilities and decreasing the cost of ocean transportation. 



MINE HOIST. 

The hoist (Fig. 195), shown on page 555, is one of Thos. A. Edison's de- 
vices used at the Ogden Mine at Edison, N. J. 

In the mine compressed air rock drills are used, and when the rock is 
finally broken and lies upon the bed, a bridge, which is poised transversely across 



ttSfi. 



555 



the mine, and it fitted with crane and hoist appliances, is brought to a standstill 
over the rocks, that are often excavated in lumps weighing four tons (8,960 lbs.). 
These are chained, and a swinging compressed air hoist is attached. By the ap- 




FIG. 195. — COMPBESSED AIR OPEN CUT MINE HOIST. 
The swinging cylinder is the Compressed Air Hoist. Five of these hoists are along the rail of the bridge. 

plication of air to the cylinder, the rocks are rapidly elevated to where the skips 
lie, and in which they are placed. 



HANDLING BAGGAGE BY COMPRESSED AIR. 

The illustration (Fig. 196), on page 556, will at first sight impress our 
readers as a very desirable and clever use of compressed air. 

Mr. G. H. Wall, of Cadillac, Mich., who is connected with the Grand 
Rapids & Indiana Railroad, last spring built and applied the pneumatic baggage 
handler shown in our engraving. This device proved itself, in daily work, 
able to handle heavy baggage more rapidly than it could otherwise be handled, 
and to, moreover, do away with breakage of baggage. It consists of a very 
simple arrangement of air cylinder and baggage support. The cylinder rests on 
the threshold of the car door. The upper portion of the baggage support is semi- 
tubular in form and is swiveled to the cylinder; and one side of this tubular 



556 



USE. 



portion is cam shaped and bears against a plate placed just above the door. Thus 
when the support is rising it is automatically swung around by the cam action, 
carrying the baggage into the car. The device is operated by air drawn from the 
train line to a special reservoir and is handled by the train baggage man by means 
of suitable cocks on the inside of the car. It has a lifting capacity of 500 lbs., 




FIG. 196. — BAGGAGE HOIST. 



with 70 lbs. of air. An auxiliary spring scale device, located at about the center 
of the vertical length of the baggage support, provides for weighing the baggage 
as it is handled. It is said that the time consumed in loading a trunk of 218 lbs. 
was 35^ seconds, and the time of unloading 5^ seconds. For country stations 
the above appliance will save many a trunk from being smashed, because only 



USE. 



557 



one man usually attends trains at such points, and the result of one man handling 
a heavy trunk is well known. 



CINDER HOIST ON THE D: S. S. & A. R. R. 

The accompanying illustrations from the Railway Age, show a cinder hoist 
that has been in successful operation on the Duluth South Shore & Atlantic Rail- 
way at Marquette for the past two years. It is operated by air and is estimated 
to be a money-saver to the extent of at least $600 a year. With this arrangement 




FIG. 197. — CINDER HOIST IN D. S. S. & A. RY. 



five iron buckets can be hoisted, dumped and replaced in the pit again on an 
average in 15 minutes, removing in the operations the same quantity of ashes as 
would take a man with a shovel at least three hours to handle. The ashes are 
raked from ashpans directly into the ash buckets, and the same is done with 
cinders in the front end, no shoveling being reqaired. The act of hoisting and 
clumping is done by the engine hostler and his assistant. 

A sunken track will be noticed located parallel with the cinder pit (the 
distance from centre of cinder pit to centre of this track being about 10 feet), on 
which is standing a cinder car, which was built especially for this service. One 
of our views shows the bucket containing the cinders hoisted out of the cinder pit ; 
the other view shows the bucket dumped over the car. When not in use the crane 
is swung around alongside the end of the round-house. 



558 



USE. 



The hoisting cylinder is hung to a four-wheeled truck on top of the crane, 
the piston of the horizontal cylinder being attached to the truck. Air is admitted 
at either end of the horizontal cylinder alternately for pushing out the loaded 
bucket to the proper position for dumping and pulling it back after being dumped. 
Air is furnished from the shop air plant. When shops are not working, any 
engine having its fire cleaned can couple to an air hose coupling attached to the 
crane and perform the operation of hoisting and dumping the buckets. 

The crane has a radius of about 30 feet, and by manipulating the horizontal 
cylinder properly the buckets may be dumped anywhere on a 32-foot car without 




FIG. 198. — CINDER HOIST ON D. S. S. & A. RY. 

moving the car until it is loaded. The old way of loading the cinders was to keep 
a man continually shoveling them out of the cinder pit into the car, at a cost on an 
average of $50 per month. Now the cost of getting rid of the cinders is practically 
nothing, as far as labor is concerned. The whole cost of the plant, including the 
five iron ash buckets, was I2.50, 



A TELESCOPIC AIR LIFT. 

The cut shows a recently patented air hoist which may be found serviceable 
in some special situations where a considerable vertical lift is required with only 
a limited space in which to move. A specially designed valve is used in connec- 
tion with the hoist, but this it is not necessary to describe, as any valve may be 



USE. 



559 



used which will admit compressed air from the service pipe for hoisting and dis- 
charge to the atmosphere for lowering, accordingly as the valve is moved in one 
direction or the other. 

As will be seen, the arrangement consists of one cylinder moving within 
another, with a piston in the inside one and a rod passing down through a central 




American MaehinUt 
FIG, 199. — A TELESCOPIC AIR LIFT. 



Stuffing box for hoisting. Obviously more cylinders, one within the other, might 
be used if a greater vertical travel was required. The cut shows both the inner 
cylinder and the piston within it at the upper limit of their travel, and sustained 
in that position, we may assume, by a pressure of air. The area enclosed between 



56o USE. 

the inside of the outer cylinder and the outside of the inner cylinder is somewhat 
greater than the internal area of the inner cylinder, so that in hoisting the inner 
cylinder will always be hoisted to the top before the piston within it begins to 
rise. In lowering, this movement is reversed, the piston first descending and then 
the cylinder. This is necessary because there is no air passage to or from the in- 
terior of the inner cylinder except when it is up, and then holes (a) at the bottom 
are uncovered. With the parts in the position shown, if the valve is gently 
opened and the air permitted to escape slowly from the outer chamber, it will also 
pass out from under the piston, and the piston will descend, and when the piston 
reaches the bottom its cylinder will then begin to descend, if the discharge of air 
continues. For hoisting, as there must be no pressure above to resist the pressure 
below, vent holes are provided in the upper heads of both cylinders. Leather 
packing is used at the top against the inner surface of the outer cylinder and at 
the bottom against the outer surface of the inner cylinder, and also for the piston 
inside the small cylinder. The inventors are Charles O. Bulock and Bertram C. 
Donnelly, Milwaukee, Wis. 



A SELF-PROPELLING AIR-HOIST, WITH UNLIMITED TRAVEL. 

Following are the description and illustrations of a novel and remarkable 
traveling air-hoist which cannot fail to excite the interest of shop readers. It is a 
complete air hoist, which travels as far as the overhead rail extends in either 
direction, going around curves, or switching to other lines, as required, with a 
constant connection with the air supply, all under the control of the operator, 
who rides with it. It is, however, not necessary for an operator to ride with the 
trolley, as it can be made to travel between points, starting and stopping auto- 
matically. In that case the hoist and motor are operated by pendants from the 
floor. The motor and the hoist, wherever they may be along the line, are both 
always in full connection with the air supply, and without any hose to look after 
or any outside connection. 

The means by which the air supply is conveyed to the trolley and the con- 
nection constantly maintained are not shown herewith but work satisfactorily. 
Along the runway of I beams is suspended a feed pipe of cold-drawn steel tube, 
and this is covered by a thin steel casing, which normally is closed, but which is 
capable of springing apart at the bottom. The air tubes are in 8-foot lengths, 
and are joined together by couplings which form a bearing for a valve in each with 
the valve operating mechanism. The couplings and the pipe have a true and 
uniform continuous surface externally. Surrounding the air pipe is a flexible 
receiver of such diameter as to allow a given area between the outer wall of the 
feed pipe and the inner wall of the receiver. The receiver travels with the trolley, 
and connection is made to the trolley through a hollow arm which is a part of the 
receiver and extends down through the slot in the casing. The lengths of the feed 
pipe being 8 feet 6 inches from center to center of valves, the length of the 
receiver is 9 feet, so that one valve is always open inside the receiver. The ends 
of the receiver fit the outside of the feed pipe with self-packing stuffing boxes. 



USE. 



561 




FIG. 200. — DETAILS OF AlK HOIST. 



ATntrican Maohiniit 



562 



USE. 




FIG. 201.— TROLLEY AND MOTOR. 



USE. 



563 




Amtrican Machinitt 

FJG. ZO^. — TROLLPY AND MOTOR. 



564 USE. 

These ends, externally, are made conical, so that as the receiver passes along the 
pipe the conical surfaces raise the tappets attached to the valve levers. The 
conical mouth of the receiver raises the tappet, and a longitudinal rib within the 
receiver keeps the tappet up until it emerges at the other end of the receiver. 
When both tappets of either lever are up the valve connected with the middle of 
the lever is raised, and when the tappet drops the air valve is closed again. Sup- 
posing the receiver to be moving to the left, the right-hand valve is seen to be 
open, and the first tappet of the left-hand valve lever has been raised. When the 
second tappet is reached and raised, the left-hand air valve will be open, and 
almost immediately, if the movement of the trolley and receiver continues, the 
right-hand valve will close, and thus the valves will be opened successively and 
the pressure in the receiver will be maintained. 

Fig. 201, showing the trolley and motor, requires little explanation here. 
The motor is of the three-cylinder type. With the pressure applied to the outer 
ends only of the cylinder the trolley can attain a speed of 400 feet per minute, if 
necessary. The motor runs at such a speed as to develop all the power required to 
move the trolley with its heaviest loads; the motor shaft carries a small pinion 
which connects with the largest gear, and small gears on the same shaft connect 
with intermediate gears that mesh into gears on wheels on both sides of the 
trolley. Levers for reversing and for the throttle are provided. After the air has 
done its work in the motor, instead of allowing it to exhaust into the atmosphere, 
it is led through another hollow arm back into the casing, which naturally creates 
a stronger air pressure flowing from within the casing than the atmospheric 
pressure without, thus preventing the possibility of dust settling on the feed pipe 
and valves. This exhaust air at the same time carries oil in the form of spray 
from the motor, which serves to keep the feed pipe well lubricated. 

At switching points the pipe casing and beam are broken in order to shift 
the main track to the switch track. The switch ends of the feed pipes are plugged, 
and the air supply is led to the other ends of the pipes. 

The hoist, Fig. 200, has some original features. In air hoists, as usually 
operated, the air for hoisting is admitted under the piston, and when the load is 
to be lowered this air is discharged into the atmosphere, the weight of the load 
being sufficient to bring it down, although when there is no load the weight of the 
piston and rod is not always sufficient except for very slow movements. The 
usual air hoist, therefore, normally has no air pressure upon either side of the 
piston. In the present hoist there is full air pressure upon both sides of the 
piston, except when hoisting. The air pressure is conveyed to the lower side of 
the piston by means of the vertical pipe seen within the cylinder. The upper end 
of this pipe is in constant communication with the air supply, and the lower end 
of it in as constant communication with the lower end of the cylinder. There is 
a stuffing box in the piston where this pipe passes through it. The pisfon also 
has on both sides of it a wooden block, which serves as a buffer and prevents 
the shock of metal to metal when the piston touches either end of the cylinder. 
No operating valve is connected to the lower end of the cylinder. When a load 
is to be hoisted the pressure is released from the upper side of the piston and the 
hoist ascends. For lowering, the pressure is readmitted above the piston. When 
the pressure is on both sides of the piston there is an unbalanced pressure down- 



^T^T^ 



USE. 



565 



ward equal to the area of the piston rod below, and this differential pressure 
operates in addition to the weight of the parts to cause the piston to descend. 
This apparatus is made by the Pneumatic Crane Co., Pittsburg, Fa.— American 
Machinist. 



PNEUMATIC FURNACE DOOR HOISTS AT PARKGATE. 

At the Parkgate Iron and Steel Works an effective method of lifting or low- 
ering the doors of the open-hearth furnace by compressed air is in use. 

The air is compressed by a Westinghouse pump fixed on to the wall of the 
power station building. The pump is shown in Fig. 203; besides operating the 




FIG. 203. — WESTINGHOUSE AIR PUMP, PARKGATE WORKS. 



hoists for the furnace doors it also works some pneumatic tools, and the feed- 
motion of the hot saw. It gives air at 80 lbs. pressure. This form of pump has 
for some years been employed on locomotives in connection with the -Westing- 
house Brake with the most satisfactory results, there being over 30,000 in use for 
this purpose alone. Owing to their small size, their compactness, portability, and 
the readiness with which they may be fixed to a post or wall by means of four 
bolts only, they are very suitable where space is the chief consideration. In min- 
ing work, being self-contained, they may be lowered down shafts and suspended 
by a chain ; and, having no dead point, they may be started and stopped from a 



566 



USE. 



Al 



FIG. 204. — VERTICAL PNEUMATIC HOIST. 



USE. 567 

long distance. The consideration of space was the one which determined their 
use in the power house at the Parkgate Works. The Westinghouse type of pump 
is of so familiar a design that we will not take up space in describing it. We 
may remark, however, that the valves of the air cylinder are of the ordinary de- 
scription. Each upward stroke admits air below the piston, and discharges air 
from above the piston; and each downward stroke does the reverse. The valves 
may be easily removed and examined. The lift of the discharge valves does not 
exceed 1-32 inch. The pumps have lo-inch air and lo-inch steam cylinders. 

The air hoists used at the furnace are of the vertical type, and were fur- 
nished by the United States Metallic Packing Company, of Bradford. The 
hoists are 5 inches diameter and 4 feet stroke, having a lifting capacity at 80 lbs. 
air pressure of 1,410 lbs. With this size of hoist, 3^ cubic feet of air at 80 lbs. is 
required- to lift the maximum load 4 feet. The hoists have self-closing valves, 
safety check, oiling device, automatic stop, and ball and socket hook'. The cylin- 
ders are made of special steel tube. The valve is self-closing by means of a 
spring, as soon as the hand chains are released. An adjustable stop is attached 
to the piston-rod, so that the load may always be stopped at the same point if 
desired. A safety check is fitted so that the load cannot fall in case of the break- 
age of air hose while hoisting. 

Speed adjustment is provided to govern rate of hoisting, or lowering. These 
hoists are made with a standard lift of 4 feet. The air hoists at Parkgate are 
provided with balance to take the weight of the furnace door, so that the hoist has 
only to overcome the difference. 



THE BUTTON PNEUMATIC BALANCE LOCKS FOR CANALS.* 



By Chauncey N. Dutton, New York, Member of the Institute. 



These locks float on compressed air confined in their lower open-bottomed 
air chambers, whence it displaces water. Each lock carries a gated lank contain- 
ing sufficient water to float the boats. When one lock descends the other ascends, 
the descending lock impelling the air from its air chamber into the air chamber of 
the ascending lock through a 13-foot, valve-controlled connecting type. No com- 
pressed air is discharged into the atmosphere or wasted. The moving force is an 
excess of weight in the descending lock, in which the draft of water is one foot 
greater, such "surcharge" being 330 tons. The greatest energy-rate is 1,150 horse- 
power; the average, 115 to 150 horse-power. 

At Cohoes, the lift is 144 feet. At Lockport, the normal lift is 57 feet 5 
inches, and the extreme lift, when floods raise the upper level, 62 feet 5 inches. 



♦An address delivered before the Franklin Institute, Philadelphia, November 16. 
1897, on the "Pneumatic Balance Locks," approved by the State Engineer and adopted 
by the Canal Board of the State of New York, to replace five pairs of lift locks at Lock- 
port, and two pairs of guard locks between Lockport and Buffalo ; and sixteen pairs of 
lift locks, known as "The Sixteens," at Cohoes, on the Erie Canal, in New York State. 
Revised by the author for publication. 



568 



USE. 



The least draft is 12 feet; the width, 28 feet at the bottom and 30 feet at the top; 
the clear or effective length 310 feet. 

They will pass up-stream two boats drawing 12^ feet and carrying each 
1,350 tons, or 2.700 tons of cargo per lockage; and down-stream two boats draw- 
ing 13^ feet and each carrying 1,450 tons, or 2,900 tons of cargo per lockage. 

They will make their stroke in one minute, and, allowing for entry and exit, 
are expected to detain boats eight or ten minutes. 

The locks are built of steel. 

Each has an upper, gated lock chamber, and a lower, open-bottomed air 
chamber containing compressed air, on which it ffoats, and as the volume of its 




^^' fsfl 






FIG. 205.— COHOES PNEUMATIC LOCKS— ERIE CANAL. 



air-charge is varied, moves up and down in a pit or deepened portion of the lower 
level of the two which they connect. 

The locks are kept from tilting sidewise by guides, and from pitching end- 
wise by an automatic leveling apparatus, consisting in fixed racks, anchored to 
terra hrma ; parallel racks built on the locks, and hollow built up shafts armed 



USE. 



569 




i *"." '^' ^bC^ til — L 




I 



willi pinions, which mesh with the opposite parallel racks, on which they hang, 
without other bearings, and between which they roll when the lock moves. 

The air chambers are so proportioned that they automatically differentiate 
the air pressure, so that the lock which descends forces the elevated lock up 



570 USE. 

against its anchors with an effort exceeding by one-third the weight of said lock 
and its load, so that it may be connected with the upper level, and used in the 
roughest manner with entire safety. 

The devices to retain the elevated lock against the unbalanced hydrostatic 
pressure, and the gates and other parts which are liable to ramming, will sustain 
ramming by boats going 3 miles per hour. 

If injured boats sink in a lock, it can be used as a dry dock. 

The locks can be raised clear of the water for painting and repairs. 

At Lockport, each lock weighs 1,500 tons, and will contain over 4,500 tons 
of water. The weight in motion exceeds 12,000 tons. 

The first locks at Lockport, opened in 1825, passed boats 3 feet 5 inches 
draft, 14 feet 5 inches wide, 78 feet 8 inches long, carrying 80 tons. They were 
replaced about 1838 by the present stone locks, which pass boats 6 feet draft, 17^^ 
feet wide, 98 feet long, carrying 250 tons. These locks are in a remarkable state 
of preservation for old limestone masonry exposed to our northern winters. The 
stone shows little decrepitation, and most of the joints are still tight, showing that 
the cement was good. 

The detention at the present locks is frequently several hours, and never 
less than one hour, because the fleets have to be broken up. The new locks will 
pass double-headers in eight to ten minutes. 

The present stoi^e locks cost $698,000. The first estimate for the steel 
locks, made in December, 1896, was $576,000, but when completed plans were 
adopted by the Canal Board, June 24, 1897, the estimate was put at $499,000. The 
market prices of steel and machinery fell sharply in the interim, but have now 
advanced ,and when the enlarged locks are put under contract, which will he 
when the Legislature makes appropriation for them, the work will cost about 
$1,000,000. The Cohoes locks will cost one-half more. 

It will be seen that the new locks at Lockport will cost about one and five- 
eighths the cost of the stone locks. They will handle units twelve times as large 
in one-sixth of the time. The dollar invested in them has, therefore, more than 
forty- four times the earning power of the dollar invested in stone locks. 

The charactertistic features of the locks may be described briefly as follows : 

(i) Compressed air is substituted for water as the element of translation 
and support of the locks and vessels. Increasing the height of lift does not in- 
crease the pressures, and, therefore, locks of any height are practicable and much 
cheaper in first cost and in operation than a flight of low lift locks. 

(2) The working pressures are very much reduced, the maximum being 
about one and one-half times the draft. 

(3) The motion of translation is uniform, having no tendency to acceler- 
ate, being regulated by the velocity at which air can pass through the conduits 
with the given head. 

(4) The locks have absolute immunity from falling. The pneumatic 
lock falls up, if it falls at all. It is pressed up firmly against the anchors with 
an effort much greater than the weight of the lock and its load. If the anchors 
yield, the lock is forced up to a height such that the air in the air chamber is ex- 
panded to equilibrium with the load, and a volume of water equal in weight to 



572 USE. 

the difference between the load and its initial excess of buoyancy enters the air 
chamber. 

(5) The speed can be very great, because air flows at high velocity with 
a slight head. 

(6) Working the locks in balance, by slight differences in weight, saving 
95 per cent, of the water heretofore used, and avoiding heavy currents in the 
canal sections. 

(7) The water-trap valve for controlling the air conduit. 

(8) The powerful automatic leveling, or synchronizing gearing, of con- 
struction cheap, such that the price per pound does not increase with increased 
power. 

(9) Dispensing with the dry-dock necessary in other types of lift lock 
and operating the locks directly in the lower level of the canal, in a pit ; the pit in 
which the locks work being part of the lower level. 

(10) The substitution of steel, mainly in tension, for masonry in the lock 
structures. 

(11) The substitution of elastic resistance for mere stability due to dead 
weight, and the consequent reduction of strains due to shock, so that they can be 
taken care of economically. 

The principal elements of design are : 

(i) The locks, which float and work in a pit formed in the lower level, 
and are identical structures, each having an upper gated lock chamber for the 
vessels and water to float them, and a lower open-bottomed air chamber contain- 
ing the compressed air on which they float. 

(2) Valve-controlled air conduits for transferring air from one lock to 
the other during translation. 

(3) Anchorages to restrain the super-buoyant elevated locks. 

(4) Guilding structures to prevent the locks from tilting sidewise. 

(5) Automatic leveling, parallel motion, or synchronizing apparatus, to 
keep them from pitching endwise. 

(6) A pneumatic accumulator, which is connected with the elevated lock 
and maintains a constant working pressure therein, automatically compensating 
for changes in density and temperature of the adjacent atmosphere. 

There are other important elements connected with the locks, which, while 
desirable, are not absolutely essential, namely: 

(7) Hydraulic stops and accumulator-intensifier, by which the elevated 
lock can be perfectly controlled and adjusted in position. 

(8) An interlocker, or sequence machine, which orders the operations 
incident to the motion of the locks, by means of valve-controlled compressed air 
transmissions. 

(9) Automatic stop machines, one geared to each lock, adjustable to 
varying water levels, which prevent the locks from running away and auto- 
matically control the variations in depth of water when elevated. 

A recital of the difficulties will aid in forming a clear conception of the 
motive and functions. A lock is the heaviest of engineering structures, carries 
per square foot a load greater than the load per running foot of the heaviest rail- 
road bridge, and is subject to tremendous and cumulative distorting forces, which 



USE. 573 

necessitates that the structure be of simple type and extreme power, and auto- 
matically leveled and controlled by apparatus strong enough to beyond preadven- 
ture arrest distorting forces in their incipiency and annul their cumulative ten- 
dency. 

The locks are liable to be bumped and rammed and to have boats carry 
away the outboard gate and sink with the boat's nose overhanging the end of the 
lock. A boat in this position, half the length of the lock, or a boat of said length 
sunk in one end of the lock, would overload that end with a weight equal to the 
weight of the boat and cargo. The leveling, or synchronizing apparatus, must be 
powerful enough to sustain this distorting effort and distribute it, and, further- 
more, it must be automatic, for were the least interval of time to intervene be- 
tween the application of the distorting forces and the action of the leveling appa- 
ratus, the loaded end would pitch, the water would run off the opposite end and 
pile up in the loaded end, giving a cumulative effect, combined with shock, which 
must inevitably destroy any non-automatic apparatus, how strong soever it might 
be, and ruin the lock. 

DESCRIPTION OF THE LOCK STRUCTURES. 

The lock structures are identical. The lower part is an open-bottomed air 
chamber, the roof of which forms the floor of the gated lock chamber. 

The air chamber is formed in eight bays, to avoid beam strains and framing 
in the side walls, which are segments of cylinders tied transversely at the points 
of intersection. The cylindrical segments do not quite meet, being united by 
longitudinal plates, and the ties are in double lines, so that by lacing them 
together stiff transverse strut members can be formed where desired. Strut 
members are so formed at the bottom and at two intermediate horizontal planes, 
where chord plates are united with the walls, so that the entire chamber is a huge 
box girder. In its normal uses the walls and cross-ties are subject to tension 
only, and are in equilibrium, not tending to change their form, but accidental 
extraneous forces may tend to cause compressive strains, which the structure 
will sustain. 

The roof of the air chamber, which also forms the floor of the lock chamber, 
is framed on heavy plate girders. 

The hydrostatic pressure on the side walls of the lock chamber is sustained 
by brackets ; those on opposite sides being tied by the floor plates. 

The gates are crescent-shaped box girders, moving orbitally on a wheel, 
and when open lie out of the way in segmental side pockets. 

The seating faces ere concentric with the vertical axes about which the 
vertical axes about which the gates move orgitally. 

The gate-opening engines have each a cylinder 14 inches bore, 8 feet stroke, 
the piston moved by compressed air, the piston rod carrying a cut steel rack, 4 
inches pitch, 7 inches face, which meshes with and turns a pinion keyed to one 
ciul of a shaft, on the other end of which is a sprocket wheel geared by a Yale & 
'JV)wne 9-16-inch chain to a sprocket wheel on a vertical shaft, secured in bearings 
on the gale post. This driving shaft has spur pinions at top and bottom, which 
mesh with pin-wheel segments on the gate. When the piston moves, the con- 
nected rack turns the shafts and pinions and operates the gate. 



574 



USE. 







FIG. 208.— AIR CONDUIT AND VALVE. 

ber of brackets and lessened by the elasticity of the guard timbering, its rubber 
supports and the plates. 

When the lock is elevated, as aforesaid, it is superbuoyant, having an excess 
lift exceeding the accidental increase of load which might occur through the sink- 
ing of a loaded boat, and this excess lift is restrained by anchors, v^^hich are 
steel plates secured to the bed rock, and encased in asphaltic concrete piers. On 
them are built the side guides and the fixed racks of the leveling apparatus. These 
are disposed in four transverse lines at the end and alternate intermediate sec- 
tions of the bays. 

When the ascending lock comes to rest, its momentum is absorbed without 
shock, by hydraulic stops swiveled on the anchorages, with which the elevated 



The gate is lightened by a flotation chamber, which floats 74 per cent, of its 
weight, leaving 26 per cent, on the wheel to give stability. The air which fills 
the flotation chamber is constantly renewed, so that the gate will not get loggy. 

The gates which are liable to be rammed contain elastic trusses, with a 
yield of 10 inches, which cushion the blow and deliver it to the gate posts, so 
that ramming has no effect on the gate itself until the elastic trusses are broken. 

The gate openings are slightly wider than the locks, so that the jambs are I 
not liable to ramming, being protected by the guard timbering on the lock walls, I 
which is as elastic as possible, to that end being supported in the centres of the 
plates on rubber cushions, so that the effect of impact is distributed over a num- 



USE. 



575 



lock engages, by brackets armed with timber contact pieces, which are readily 
movable, to allow the lock to be raised clear of the water for painting and repairs. 

AUTOMATIC LEVELING, OR SYNCHRONIZING APPARATUS. 

During the years which have been devoted to developing the pneumatic 
lock, many different types of leveling apparatus were considered and more or less 
worked out, but were all prohibitive in cost, especially on a large scale. The 
characteristic features of that adopted are that it is always in action ; has only 
rolling friction, normally sustains only its own weight, has the minimum wear 
and abundant end clearance, which prevents binding and temperature strains. It • 



e^ 







FIG. 209. — AIR VALVES. 



can be made of any power, and the larger it is made, the less will be its cost per 
pound. It does not require nice workmanship, or careful adjustment. It is what 
engineers call a "brute." 

Its elements are vertical racks securely anchored to terra firma, parallel 
racks built integral with the lock; hollow riveted steel, rolling shafts parallel with 
the locks and carrying pinions which mesh with the opposite parallel racks on the 
lock and on terra firma, the shaft having no bearings, but hanging upon its en- 
gaged teeth. When the locks move, the shafts roll between the racks and tra- 
verse one-half the stroke of the lock. 

The preferred form of rack is the ladder type, with pin teeth. Small lock 
pinions may be cast. For large locks they must \k built up of rolled steel, th« 



576 USE. 

core a forged drum, the blanks rolled steel rings with involute cut teeth. Such 
a gearing would give undue wear, were it always subject to maximum working 
pressures, but for a lock it is, perhaps, the ideal form, as normally the teeth carr> 
only the weight of the shafts ; the maximum pressures, due to accidental unequal 
loading, being infrequent. In the Lockport locks the shafts are 4 feet in diameter, 
made of inch plate. 

The pinions are double, cut on rolled blanks, 6 inches thick, the involute 
teeth 16 inches pitch, 60 square inch section at pitch line, 16 pinions and 960 square 
inches of metal in the teeth being in action. 

The outside rack stringers are 15-inch channels, with inch webs, and the 
teeth 6-inch pins, riveted in. 

AIR CONDUITS. 

The air main is 13 feet in diameter, and will transfer the entire air charge 
from lock to lock in one minute, with 330 tons surcharge in one lock. 

The connection with each lock is by two open-ended standpipes, 10 feet 
diameter, which extend from the bottom of the lock pit considerably above the 
water surface, under hoods formed in the lock body. From their ends rock-cut 
tunnels run to the risers, which connect with the main valve. 

The main valve is a "U" bend, provided with water inlet and drain pipes, 
so that the bend may be trapped with water and untrapped to shut off or permit 
the flow of the air. 

The water-supply and drainage to and from the valve is controlled by 
pneumatic weirs, which are the reverse in principle of the air valves. A water- 
feed pipe extends from the upper level of the canal to the Lower part of the main 
valve, and is formed like an S, with upper and lower bends. A similarly formed 
drain connects to the bottom of the main valve, rises to an upper bend and 
descends into and is sealed in the water of the lower level. 

Air-supply pipes lead from the upper bends of the said water-feed and 
drain pipes to a 6-inch double-acting air valve, which is part of the interlocking 
machine in the operator's house. When this 6-inch air valve is moved to "feed"' 
the air to the weir of the water-feed, and to "waste" the air of the drain weir, 
the air pressure enters the upper bend of the feed and seals it against the passage 
of water; at the same time the air pressure wastes from the upper bend of the 
drain and the water drains out of the main valve, opening it to a passage of the 
air. 

\\*hen it is desired to close the main valve, the 6-inch air valve at the inter- 
locker is moved to "feed" the air pressuse into the weir of the drain and to 
"waste" air from the weir of the feed. The' air escapes from the feed weir and 
permits water to flow from the upper level into the main valve and seal it, and 
such water seal is prevented from escaping by the air-trap in the upper bend or 
weir of the drain. 

Similar valves, 4 feet in diameter, open into the legs of the main valve and 
connect by a 4-foot main with a pneumatic accumulator, which may be thereby 
c(»iiiiected with or cut off from either lock. 

PNEUMATIC ACCUMULATOR. 

The pneumatic accumulator is a cylindrical bell, or open-bottomed air 
tank, having an upper weight chamber filled with water, and gives a constant 



ABl 



USE. 



577 



working air pressure. When a lock is elevated it is immediately' connected with 
the accumulator, which maintains a constant working pressure and automatically 
compensates for varying density and temperature in ♦the adjacent atmosphere, 
which would otherwise vary the working pressure. 



INTERLOCKING APPARATUS. 



In order to prevent the operator from making mistakes, all the operations 
necessary to translate the locks are controlled by an interlocking apparatus, or 
sequence machine. This machine has five levers, on vertical interlocked stems, 
which are geared to horizontal shafts carrying-cranks directly connected with the 



Jnieric 







FIG. 210. — AIR VALVES. 



Stems of air valves, so that when the operator swings a lever he directly operates 
an air valve, and at the same time locks the lever behind him and unlocks the 
lever in advance, in order of sequence. 

All the transmissions are by compressed air, and are controlled by the 
aforesaid valves of the interlocker, and critical motions are further controlled by 
stops operated by compressed air piped to them from valves at the gate posts, so 
that if any gate be off its seat the apparatus is firmly locked and cannot be moved 
until each and every gate is properly seated. 

The interlocker is in a three-story operator's house, all the valves and pipes 
being in the lower, the operating story containing only the levers and the table 
which carries them. 



578 USE. 

The tubular valves have balanced spools, cup-leather packings and bronze- 
lined shells. 

AUTOMATIC STOPPING MACHINES. 

The automatic stop machines prevent the locks from rising too high, or 
running away, and control the amount of surcharge taken on the elevated lock, 
which is the working force of the system. To this end, they control the hydraulic 
valves of the hydraulic stops. 

Because air is elastic, the motions of the ascending and descending locks 
are not exactly synchronous, the ascending locking leading the descending lock. 
Therefore, stop machines are independent for each lock. They operate only when 
the lock is in the upper limit of its stroke, and are adjustable to compensate for 
varying heights of water in the upper level. 

Each lock operates its machine by chain gearing turning its main shaft, 
which carries a drum having a differential thread, one end being of i-inch pitch, 
the other 36-inch pitch, the latter cut in an enlarged part, the slow thread being 
idle, merely keeping the parts in mesh while it is not desired that the lock should 
function the machine. 

The thread moves a sliding bar, which has on one face a differential tooth 
meshing with the thread of the drum, and on the other an operating face, con- 
sisting in a rack and plain guiding surfaces coincident with the pitch lines of the 
rack. Engaged with this bar is a pinion segment, having a toothed portion and 
plane faces tangent to the pitch circle. 

During the greater part of the lock stroke the differential tooth meshes 
with the slow thread on the drum, the plain faces of the bar and segment engage, 
and the machine does not function. When the lock approaches the upper limit 
of its stroke, the differential tooth meshes with the quick thread, the rack meshes 
with the toothed portion of the segment, and the machine functions ; the shaft 
carrying the segment being connected with a parallel crank shaft by double gear- 
ing, the gears on the crank shaft being loose and rotating it by ratchet gearing, 
so that it is always turned in the same direction, whichever way the segment 
may be rotated. One end of the crank shaft connects by a crank and link with 
the main hydraulic valve. The other connects with a positive differential crank 
motion directly actuated by compressed air from the interlocker, and such that 
dead centres are avoided and the slip of the valve is taken up twice during the 
complete cycle. The lock opens and closes the hydraulic valve by rotating the 
segment. The operator opens the said valve, and takes up slip, and brings it to a 
fixed position by admitting compres.sed air to a piston of the differential apparatus, 
which is so geared that when the differential crank rotates 144°, the valve crank 
rotates 210°, and when the lock rotates the valve crank 150°, completing its revo- 
lution, the differential is rotated 216°, and completes its revolution. 

HYDRAULIC ACCUMULATOR INTENSIFIER. 

This machine gives the operator perfect control of the elevated lock. It is 
so designed that by operating a valve it will give either a higher or lower work- 
ing pressure. When the lower pressure is admitted to the hydraulic stops, the 
lock will retract the stops and raise the accumulator weight. When the higher 
pressure is admitted to the stops, they will force down the lock. 



USE. 



579 






1 







1 


II iii 





1 1 

II iiy. 

1 


1 III 

1 1 


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. 

























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1 






1 















FIG. 311. — LOCK FOUNDERED. 



LOCK AFLOAT— READY TO ASCEND. 



58o 



USE. 



The weight is a tubular concrete block, with an annular water tank for 
increasing the load. The frame is central in the well of the weight and sustains 
the hydraulic members, which are a lower 20-inch cylinder, a 20-inch ram carry- 
ing the weight and bored to form the cylinder for an upper ii^-inch ram work- 
ing therein. 

The two cylinders are connected by a valve-controlled pipe. When the 
valve is closed, all of the water expelled from the 20-inch ram is piped to the 
hydraulic stops, the pressure being 1,086 pounds. When the valve is open, one- 
third of the water expelled from the 20-inch cylinder goes into the ii^-inch 
cylinder and intensifies the pressure, raising it to 1,623 pounds. 

This is an example of work equivalent. The work done is the descent 
of the accumulator weight. If all of this work goes into the stops, their work 
collectively is equal to the volume swept through by the accumulator ram at low- 
pressure. If but two-thirds of the water passes to the stops, and one-third goes 
to the intensifier, it is evident that the same work must be done by the stops in a 
stroke two-thirds of the stroke of the weight, and, therefore, the pressure must be 
increased one-half. 

The machine is also a mechanical proof of the mathematical summation 

of series. In the case given the intensifier ram is practically one-third the area 

of the accumulator ram. Therefore, when the valve is opened, the pressure in 

the accumulator cylinder reacts through the intensifier cylinder and raises the 

pressure in the accumulator one-third. This one-third reacting in the same 

manner, raises it one-ninth. The one-ninth increase raises it one-twenty-seventh, 

which raises it one-eighty-first, which raises it one-two-hundred-and-forty-third, 

and so on to summation: 

III I I 

-+- + + + + 

3 9 27 81 243 

et cetera, the sum of which is one-half. 

operator's control of the elevated lock. 

Swelling the Boats In and Out. — Experience proves that the entry and 
exit of boats to and from locks is much easier if water flows with the boats. 
Therefore, the ascending lock holds a depth of water considerably exceeding the 
least working draft, and when it approaches the upper limit of its stroke is 
automatically stopped, with the water in the lock chamber on a level with that in 
the aqueduct, so that as soon as the space between the adjacent lock and 
aqueduct gates is filled with water the said gates can be opened, without adjust- 
ing water levels, thus making a great saving in time. A further saving is made 
by swelling the boat out into the aqueduct. To do this, the operator moves a 
lever at the interlocker, which opens the main hydraulic valve, the intensifier 
valve being at such time closed, whereupon the lock retracts the hydraulic 
stops, rises and discharges its surplus water into the aqueduct, swelling the boat 
out, the upward motion of the lock being properly automatically arrested by the 
automatic stop machine. 

As the boat which is to be locked down enters the lock, the operator swings 
a lever in the interlocker, which simultaneously opens the hydraulic valve and 
the intensifier valve, bringing the intensifier into action, the hydraulic stops fore- 



USE. 581 

ing down the lock, which takes on a surcharge of water, which swells in the 
boat, the downward motion being properly automatically stopped. If now the 
gates be closed, the elevated lock is ready for its traverse. 

AUTOMATIC CONTROL OF THE DEPRESSED LOCK. 

In order to avoid nicety of adjustment and loss of time in connecting the 
depressed lock with the lower level, said lock founders until its downward mo- 
tion is arrested and cushioned by the floating power of the cushion chambers at 
the sides of the lock chambers. There are longitudinal flotation chambers be- 
neath the cushion chambers, from which the air is discharged as the lock is im- 
mersed, so that the lock may founder; after which both gates are opened, so 
that the water can come in behind the boat, as it is drawn out, giving it free 
motion. 

The lock descended surcharged with water and now contains a maximum 
draft. In order to ascend, it must be lightened. For- this purpose there are 
vertical long flotation pipes, of small cross-section, which, when the lock is 
elevated, communicate with the atmosphere and take in a charge of air at 
atmospheric pressure. As the lock descends this air is held and compressed, its 
pressure being a maximum and its flotation a minimum when the lock is in its 
lowest position; at which time valves are automatically opened, permitting this 
air to rise from the narrow vertical pipes to the long horizontal flotation cham- 
bers. As it rises, the water pressure on it diminishes and it expands to nearly 
atmospheric pressure and regains its original volume and maximum floating 
power, automatically increasing the flotation of the lock so that it floats with 
just the desired depth over the sill. 

The minimum draft is 12 feet. Draft ready to ascend, 12 feet 6 inches. 
After the lock is elevated and connected with the aqueduct, it rises 6 inches, 
expels this surplus into the aqueduct, swells out the boat, and has its minimum 
draft over the sill. To take in the surcharge of water and swell in the descend- 
ing boat, the lock is forced down 18 inches and descends with 13 feet 6 inches 
over the sill. 

AUTOMATIC INCREASE AND EQUATING OF AIR PRESSURE. 

While the lock is moving, it is obvious that the air pressure cannot vary 
greatly from the pressure which would be in exact equilibrium with the load. If 
the walls of the chamber were parallel, the working margin of excess pressure 
must be greater, because the pressure of equilibrium would necessarily increase 
as the lock rose and the immersed portion of its walls became less; therefore, 
the locks are equated, so that the working pressure or pressure of equilibrium :s 
constant, the sides being splayed, so that the projected area against which the 
pressure acts increases in a constant ratio from the upper towards the lower por- 
tion of the air chamber, with the decreased immersion of the walls. 

When the elevated lock is arrested by the stops, it is necessary for its 
safe use that the air pressure and the flotation be increased some 30 per cent. 
This is done automatically by the descending lock. 

The horizontal area of the air chamber is considerably larger than the 
floor of the lock chamber, such excess equaling the sums of the areas of the 
horizontal segmental projections of the air chamber beyond the line of the lock 













FIG. 212. — LOCK FOUNDERED. 
LOAD AND AIR PRESSURE 
MAXIMUM. 



LOCK ELEVATED. 



USE. 583 

chamber. When the lock is elevated, there is no water on these plates, but as 
the lock descends they become immersed, and the weight of water upon them 
is necessarily carried by the air charge, the pressure of which is thus increased 
and becomes a maximum when the lock is at its lowest position; and this auto- 
matic increase of pressure is transmitted to the elevated lock, and there acts on 
the larger pressure surface at the lock bottom, and thus automatically provides 
the excess of buoyancy necessary to safe use. 

ELASTIC RETAINER FOR ELEVATED LOCK. 

While the lock is moving it is not subject to disturbing forces, except that 
of the wind, but when it is elevated and connected with the aqueduct, the un- 
balanced hydrostatic pressure tends to force the lock away and break the joint; 
and because boats might ram the outboard lock gate, it is necessary that the 
connection have flexibility to cushion the blow. These ends are compassed by 
tension retainers, which are I-bar cables, 220 feet long, hanging in catenaries, 
anchored at one end to the bed rock, at the other retaining the hydrostatic pres- 
sure in the end of the aqueduct, or in the lock when connected, the connection 
being retaining wheels, 12 inches thick, 5 feet diameter, with is-inch journals, 
adjustable in bearings formed in the end frames of the retainers, the wheels 
engaging shoulders on the lock, which are runways planed on heavy steel cast- 
ings, riveted into and forming flanges of the portal columns of the lock body. 
A blow will pull the cables into flatter curves, the endwise motion cushioning 
the shock. 

The joint is made water-tight by a dilatable rubber tube, secured to the 
aqueduct face, and seating at any point on a fiat timber apron provided on the 
adjacent end of the lock. The tube is cured flai, and remains so when deflated. 
To make a joint, it is inflated by compressed air admitted from a valve of the 
interlocker. The space between the gates is flooded and emptied through pipes 
controlled by pneumatic weirs, which, in turn arc controlled by air pipes leading 
to valves at the interlocked. 

POWER PLANT. 

There is a 36-inch double-balance turbine, belted to a duplex air com- 
pressor, to a four -cylinder, high-pressure hydraulic pump, and to a dynamo for 
lighting. Also a high-pressure air tank, and a tank for the hydraulic supply, it 
being intended to operate the hydraulic apparatus with 500° test petroleum. 

AQUEDUCT. 

The necessity of operating the old locks while the new ones were being 
built compelled the use of an aqueduct, 393 feet long, to connect them with the 
upper level. This aqueduct is so designed that the strains due to the static load 
oppose and cushion the strains induced by collision of vessels using the aqueduct. 
This principle develops the full elastic quality of the steel, makes the sides four 
times as flexible, and the flange strains less than one-eighth as great as those 
obtaining in aqueducts heretofore designed; the builders of which apparently 
ignored the destructive effect of shocks or assumed that the boats could be drilled 
so as not to collide. 



5^4 



USE. 




FIG. 213. 



USE. 5S5 

In structures of the old type the flange strains in the frames are due to the 
sum of the static and shock moments, and the elastic cushioning movement of 
the side walls is that due to the variation in the one kind of strain, for example, 
tension, to which the flange is subjected. In the design exhibited, the flange 
strains are equal to one-half the difference between the static and shock moments, 
and reverse from tension to compression, or vice versa, so that the elastic move- 
ment is four times as great, the greatest which the metal is susceptible of without 
injury. *" 

GENERAL PRINCIPLE OF CONSTRUCTION. 

The floor is not framed, but suspended at the edges, and the weight thereon 
exerts an inward pull on the frames in opposition to the hydrostatic pressure on 
the sides. By suitably proportioning the parts, these forces can be given any de- 
sired ratio. The inward moment of the floor exceeds the sum of the outward 
moments, and induces compression in the upper and inner flanges, and tension 
in the outer and lower flanges below the floor line. When a boat strikes the side, 
the stresses are reversed. 

This particular design could not be applied to the end bays, where the 
gates are located. Therefore, the principles were applied in a different manner, 
the flat floor being carried by transverse girders spliced to the side walls, which 
are framed as girders and connected to the inner vertical flanges of the frames 
which are suspended from their outer flanges on links and pins, so that under the 
static load the outer and under flange is in tension, and the upper and inner 
flange in compression. When the boat strikes one side, its shock is cushioned 
by the elasticity of the entire frame, and before it can have a destructive effect, 
it must reverse the strains in both flanges, swing the end of the aqueduct to one 
side and somewhat raise it. This design can be made much more effective with 
an equal weight than that adopted for the intermediate bays, because the shock 
is cushioned by the elasticity of the entire frame, whereas the other design cush- 
ions by the elasticity of half the frame. 

As the designs for the aqueducts have been very materially improved since 
this address was delivered, the reader is referred, for full information concerning 
them, to U. S. patents 621,470, of March 21, and 626,321, of June 6, 1900, issued 
to the author. 

While every precaution has been taken in the design to prepare the struc- 
ture safely to resist a maximum shock, the interior of the aqueduct is protected 
with elastic timber guards, which, if they be properly maintained, will absorb 
the greater part of the shocks without much strain to the structure. But, ob- 
viously, a structure which may be put into the keeping of incompetent men, 
appointed for political purposes without regard to their fitness, must be so de- 
signed that no fool can cripple it, so that it might be wrecked by improper use. 
Therefore, the aqueduct is designed with such great care, and is much more 
costly than would be desirable were it owned and operated by a private cor- 
poration, which would exercise reasonable care in its use and maintenance. The 
same is also true of the locks. 

HOW THE LOCKS WORK. 

The depressed lock floats and requires no care. The elevated lock is con- 
nected with the pneumatic accumulator, and the air pressure in it is 8}^ pounds 



586 



USE. 



per square inch, which expels from it a weight of water 30 per cent, greater than 
the weight of the loaded lock, giving it the excess buoyancy necessary to its 
safe use; said excess buoyancy being restrained by the anchors. When the 
elevated lock first ascended, it engaged with the retainer the joint was packed 
by inflating the rubber pipe, the space between the lock and aqueduct gates was 
flooded with water, the gates were opened, the boat was swelled out into the 
aqueduct, to accomplish which the hydraulic valve controlling the stops was 



Low Pressure in Ascending Lock, 
High in Descending. 



Descending 
Lock. 



Ascending 
Lock. 



70ffi 






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:::;:::::#::: 




::::::::::::: 




























ff — -- 


























































































































































































































4 fk 






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70 70 



60 6G 



SO 50 




40 40 



30 30 



20 20 



10 10 



O O 




iO 15 20 



FIG. 214. 



5 10 15 20 6 5 4 3 a 1 

FIG. 215. FIG. 216. 



1 % d 4 5 6 



Vertical ordinates read stroke in feet. Abscissas read feet of water pressure, or 
"head" on air charge, in Figs. 214 and 215; and in Fig. 216 read 100,000 of cubic feet of com- 
pressed air as distributed between the two locks during their cycle, the central ordinate 
indicating the position of the valve and the ndjacent rectangles the conduits, In Fig. 
1 the stroke of the descending lock reads downwardly, with the motion ; in Figs. 2 and 
3 all strokes read upwardly so as to show relatively coincident conditions in the two 
locks. 



opened and the lock retracted them and raised 6 inches. As the descending boat 
entered the lock, the intensifier was brought into action, the lock was forced down- 
18 inches and took on its surcharge of water, swelling in the boat, such lock 
motions being automatically stopped by the stop machine. The gates of the 



USE. 587 

depressed lock, and the adjacent gates of the elevated lock and aqueduct can now 
be closed, and the space between them drained. The accumuator valves are now 
closed, the main valve is opened, and the air expands from the elevated lock 
into the depressed lock, raising it and at the same time lightening it as it rises, 
by reducing the extraneous load of water on the projecting horizontal segmental 
plates at the tops of the air chambers. This function continues until the air in 
the elevated lock has expanded to less than equilibrium with the weight thereof, 
so that the elevated lock can descend, at which time the depressed lock has been 
raised so high and the extraneous load thereof so decreased, that the pressure of 
equilibrium therein is less than in the elevated lock, from which time the de- 
pressed lock ascends until it is fully elevated and is brought to rest by the 
hydraudic stops, and the elevated lock descends until the segmental plates at the 
tops of the air chambers are immersed and begin to take on the extraneous load, 
which increases as the lock descends, and the plates are immersed to greater and 
greater depth, such extraneous load and the air pressure becoming maximum 
when the lock has descended to its lowest position. This maximum pressure 
acts in the elevated lock at the large bottom portion thereof, and induces therein 
the excess buoyancy necessary for its safe use. The main valve is then closed, 
and the accumulator valve opened, connecting the accumulator with the elevated 
lock, which can then be connected with the aqueduct. Both gates of the de- 
pressed lock are then opened, which is thereafter automatically floated to a 
higher position relatively to the surface of the water of the lower level, in which 
it floats, so as to contain the draft of water with which it should ascend. 

The pneumatic lock will wholly change the conditions of canal construc- 
tion. Heretofore, the range of usefulness and the location of canals have been 
limited by the water supply available for feeding the locks from the summit level, 
and it has been necessary to maintain the water level within narrow limits; and 
the large amount of water and the heavy currents necessary in locking have 
necessitated a constantly running supply and spill ways for the escape of such 
supply, when the locks were not operated. The small lift of the Leonardo locks 
necessitated the selection of gentle slopes for the lock sites, which, in many cases, 
involves soft foundations. In canals planned with pneumatic locks, the most 
economical plan will be to make the levels as long and the locks as high and few 
in number as possible. Guard locks and the waste of water can be entirely dis- 
pensed with, and the summit level can be utilized for storage, its banks being 
high enough to contain the highest and its bottom low enough to give the desired 
draft at the lowest water, the variation being taken up at the lock. In most 
canals the heavy tonnage is one way, and down hill. In such cases the descend- 
ing tonnage will not only operate the lock, but also lift water to the summit 
level. It will be seen that the first cost of canals and their demands on the 
water-supply are reduced to a minimum. Application of steel to the locks re- 
duces their cost of installation, operation and maintenance as greatly as it has 
reduced such costs in other engineering structures. The State authorities esti- 
mate that the saving in wages at Lockport will exceed interest on the entire cost, 
and at Cohoes such saving will be double the interest on the cost of installation, 
so that building the Cohoes locks will save an actual profit. In ship canal locks 
the saving will be in ratio increasing with their size. 



588 



USE. 



THE APPLICATION OF COMPRESSED AIR TO CRANES AND 

HOISTS. 

As it is now conceded that compressed air has become the most useful and 
economical addition to a modern manufacturing establishment, and as many shops 
are now thus equipped, a brief description of its application to cranes and hoists 
would be in keeping with the times, although this is but one of the many uses to 
which compressed air is applied. The objection urged by many against the use 
of compressed air for a traveling crane has been, that there was no practical way 
of carrying air to the crane where a long travel was used, but as different cranes 




FIG. 217. — COMPRESSED AIR CRANE. 



are now in successful operation, a description of some of these should quiet their 
apprehension. 

The Ingersoll-Sergeant Drill Co. have for a long time been ardent advocates 
of compressed air as a power for cranes, and have fitted up their shops at Easton, 
Pa., completely with such ; the following description being of cranes in continuous 
operation at their works. 

Figure 217, here illustrated, is a cut of a 20-ton traveling crane in their main 
machine and erecting shop, the crane having a span of 40 ft., and a travel of 460 
ft. As it is shown by the cut, each movement of the crane is controlled by a sepa- 
rate engine, the three engines being piped to the valve box in the cage, where three 
levers control the movements of the crane. In order to avoid the complication of 
a link and two eccentrics for each cylinder of the duplex engine, a special engine 
was designed, the cylinders of which have two sets of ports, one direct and the 



USE. 



5B9 



other crossed, but having a common exhaust, the valves having both a rocking 
and a shifting motion with one eccentric only used for each cylinder. A double 
set of supply piping is run from the Viilve box in cage to each engine, so that when 
the levers are moved in either direction, opening the air to either pipe, the engine 
valves are shifted by the air coming in on one side and the engine has the desired 
movement. When the lever is reversed, the air passes through the other pipe, the 
valve is shifted to the other end of chest and the engine is reversed in its move- 
ment. 

As the hoisting engine on the carriage of the crane moves the length of the 
crane, the two pipes carrying the air to this engine are only run to the centre of 
the crane and fastened to the girders. Two lengths of hose are run from there 
to the engine, the hose being placed one in front of the other that one will pass 
through the other, and both only sufficient length to reach from the centre of the 
girder to the end. The engine which gives the transverse motion to the crane is 




FIG. 21 



set on the opposite end of crane and draws the carriage backward and forward 
with a wire cable. 

Probably the most interesting part of the crane to the general observer, is 
the novel method of carrying the air to the crane. As is clearly shown by the cut, 
this is accomplished by a continuous hose built up of 50 ft. lengths coupled to- 
gether, each coupling being made in combination with a swiveled sliding block, 
which slides on the overhead rail bolted to the roof truss and preferably made of 
I beams. In the centre of each length of hose is a clamp to hold the hase, also 
made with a swiveled slide. The hose is fastened to the building at one end and 
to the crane at the other, it being suspended at intervals of 25 ft. to the overhead 
rail by the swiveled slides. As the crane moves away from the hose, the hose is 
pulled along, each length straightening out and pulling the next length. On the 
return travel of the crane, as the sliding blocks come together, the hose falls in 
loops, the swivel in slide allowing each loop to turn around to its natural posi- 
tion, which is at right angles to the overhead track. It is thus seen that each loop 
of the hose requires only the room occupied by one sliding block on the rail, which 
was made 6 in. long, so the hose for the entire travel of 460 ft. occupies only 9 ft. 
zt one end of the shop where the crane is never used. 



590 



USE. 



The above method of transmitting air has been in successful operation for 
some time at these works and has never caused any trouble, and as it is such as 
can be used in all cases regardless of the length of travel, it can be recommended 
as the best method as has yet been devised. Should it become necessary to put in 
a second crane, the hose would be attached to the opposite end of the building and 
slide on the same overhead rail. 

Where a crane is used where there is no overhead room for the hanging 
hose, the arrangement shown in Fig. 218 will be found very simple and effective. 
This consists of a wooden drum hung at one end of the crane and of sufficient size 
to carry the length of hose required. One end of the hose is fastened to one end 
of the building, the other end being held to the hollow shaft of the hose drum, 
said shaft having sleeve and stuffing box at the end through which the air passes 
to the hoist. Underneath the hose is a board or trough on which the hose lies as 
it is unwound. On the same drum with the hose is a J4 iri- wire rope wound be- 
tween the coils of the hose. One end of the rope is fastened to the drum, the other 
end passing through a sheave at the end of the building, and having a weight suffi- 
cient to turn the drum attached to same. Referring to Fig. 218, as«Hie crane moves 
to the left, the hose, being held stationary at the right, will unwind the drum. 




FIG. 219. 

which will at the same time wind up the rope, or if moved to the right the rope 
will unwind the drum and wind up the hose. The weight on the end of the rope is 
made to keep the hose and rope taut and to wind up the hose, the sheave wheel 
allowing the weight to move up and down, this being necessary OAving to the dif- 
ference in diameter of the rope and hose and the corresponding difference in the 
length of a coil of rope or hose on the drum. The movement of weight for 100 
ft. of travel of crane is about 5 ft. The one objection to this arrangement of crane 
is that if the travel of crane is long, the drum must be large reducing the effective 
span of the crane. 

Fig. 219 shows a hand power crane with an air lift used in the foundry 
cleaning shed. Two pipes with swing joints carry the air to the crane; the centre 
joint being made with a roller runs on a circular track hung from the roof, which 
in this building is very low. The limit of travel with this crane is about three and 
one-half times the span, but can be used in many places where hose may be objec- 
tionable. 

In the foundry of this establishment there is a Compressed Air Power 
Traveling Crane similar to that shown on Fig. 217, and a Craig Ridgeway Pneu- 
matic Hydraulic Jib Crane which uses compressed air instead of steam for put- 
ting the water under pressure. This crane uses the same water continuously, the 
air only being discharged as the weight is lowered. 



USE. 591 

The air hoist has lately been receiving considerable attention, many valu- 
able improvements having been made which make the hoists more convenient 
and easily handled and brmg them into general use wherever light lifting is re- 
quired. The two general methods of applying the hoists, in addition to being 
used on a traveling crane, are first, where they are attached to the trolley of a 
jib crane, receiving their air through a hose leading from an air pipe at the crane 
post to the hoist, the latter being thus at all times ready for use; and second, 
where the hoist is hung to a trolley running on an overhead rail. With this latter 
method, the air pipe is made with outlets at specified places wherever the hoist- 
ing is required, each outlet having a length of hose with a valve and quick acting 
coupling attached to same. The hoist is moved along the rail to where required, 
the air hose coupled to it, the load lifted, the hose uncoupled, and the hoist with 
its suspended load is ready to be moved by hand or cable to wherever the overhead 
rail will carry it. This is very quick in its operation, unlimited in its application, 
and is by far the best method that has as yet been devised for the handling and 
conveying of merchandise of any description and weight from one location to 
another, or wherever an overhead rail can be conveniently carried. 

In conclusion, it should be remembered that compressed air is a power 
economically produced, clean and convenient to handle, and understood by all, 
so that wherever used, men of ordinary intelligence can be employed to operate 
the machinery and keep it in order. wm. prellwitz. 



PILLAR AND GANTRY CRANES OPERATED BY AIR MOTORS. 

The Gantry crane was made for the flask yard of Dennis Long & Com- 
pany (manufacturers of cast iron water and gas pipe), Louisville, Ky. It 
has hoisting longitudinal and cross-travel movements, all operated by inde- 
pendent compressed air motors. The capacity is five tons. The span cen- 
ter to center of track rails is 30 feet. The girders extend 10 feet beyond 
one end frame, which is open to allow the passage of the hook with the 
suspended load. The open space is 8 feet and has a full width for a height of 19 
feet. The greatest lift of hook from the ground to the highest position is 22 
feet. The extreme travel of the trolley on the girders is 34 feet 10 inches. The 
length of travel of the gantry on the surface tracks is about 250 feet. Air is fur- 
nished to this crane by means of flexible hose, which is carried on a large reel, 
not shown in cut. The operator is placed on top of the girders where the levers 
appear, in a position so that he may overlook the handling of the load. This 
crane has been very successful, and has been in actual operation for over two 
years. The expensive trestle work is avoided in the use of this form of crane, 
and the extension longitudinally is limited only by the yard room at hand. 

The pillar crane, shown herewith, is one of five (all duplicates) furnished 
the C, C, C. & St. L. R. R. (Big Four) for their coaling stations. They are 
used for both coaling locomotives and removing ashes from ash pits. The 
column is made of cast iron and the over all height is 8 feet 6 inches. The 
radius of the hook is 12 feet. The cylinder hoist is 12 inches in diameter and 
has 6 feet stroke. It is furnished with a quick acting valve, and loads are 



592 



USE. 



handled very quickly when necessary, also slowly, as may be desired, the opera- 
tion being under perfect control. These cranes are capable of coaling a large 
freight locomotive in from ten to twelve minutes, using half-ton buckets. 

The Whiting Foundry Equipment Company, Harvey, 111., who installed the 
above, has recently furnished a prominent steel manufacturing concern in the 
West with modified air hoists, to be used for charging billets into a reheating 
furnace, and also for raising table for mill. The pushers first mentioned are 14 




FIG. 220 — PILLAR CRANE. 



inches in diameter and have a total stroke of 8 feet ; are operated by air for both 
forward and reverse movements, being fitted with automatic attachment cutting 
off the supply when the limit of the stroke is reached at each end. 



SOME CONVENIENT DEVICES IN A RAILROAD YARD. 



The two accompanying engravings show how compressed air is utilized 
in the yard of the Northern Central Railroad at Sunbury, Pa. 



p^ 



USE. 



593 



The sand house containing the sand supply is at the right of a post carrying 
a pipe, on the end of which is a short length of hose, which is dropped into the 
sand box opening. The building contains four sand dryers, arranged so that as 
the sand passes through the irycrs it drops over a screen and into a largc hopper, 
from which it is finally fed into a receptacle so arranged that the opening for the 
latter can be closed, air pressure put in and sand blown from this receptacle to the 
pipe and to the locomotive sand box. 

Fig. 221 is of the ash hoist and shows the same arranged for two 
ash-pits with track on which cars may stand to be loaded with ashes between the 
two pits. The ashes are drawn from the ash pan, and the cinders from the 




FIG. 221. — ASH HOIST. 



smoke box, directly into a bucket, which can be moved lengthwise of the pit on a 
track, which is laid at the bottom. In this way they can be located conveniently 
under the locomotives and then moved under the frame and lifted by the hoist, 
which can also be made to traverse across the frame and dump the ashes into 
the cars. 

Another device is the Fig. 222, a coal wharf at Sunbury. This is also 
operated by compressed air. The cars containing coal are brought up on the low 
trestle at the back, where the coal is dumped from the hopper cars into coal 
dumps, which are moved longitudinally under the coal trestle and brought to a 
central point after being loaded where they are turned, weighed and brought to 
one of the two hoists shown elevated to the platform and run on a transfer car, 
which moves the whole length of the wharf and deposits the loaded car at any 



594 



USE. 




FIG. 222. — COAL WHARF. 

track, and also removes the empty cars in the same way, but in the reverse 
direction. The transfer table is also operated by compressed air, the same being 
done by a small air motor. 



WATER AND AIR. 

An all-important question, nowadays, is how to secure an adequate and 
wholesome supply of water. It interests the manufacturer, the farmer and the 
water committees of both large and small communities. Its importance cannot 
be o\^er-estimated. 

Until within a few years the supply taken from surface streams was con- 
sidered sufficient, but droughts and ever-present impurities have shown the 
necessity for a more careful study of the subject, and as a result we have heard 
from all sections the decision to bore through the crust of the earth and tap the 
subterranean streams which are known to exist almost everywhere. Sometimes 
this water-bearing strata has been found within 20 or 30 feet of the surface, as, 
for instance, on Long Island. And again, it has become necessary to bore looo 
to 2000 feet, as is the case quite often in Texas. 

The water secured from these underground sources is more wholesome 
and less apt to be contaminated than that taken from the surface streams, and 
this is because the sand and gravel through which it percolates acts as a filter 



USE. 



595 



more effectually than any device patented by human being. Whenever it is re- 
ported that this or that town's water is impure and dangerous to public health, 
it will be found that the source of supply is a surface stream, and seldom, if ever, 
do we hear of sickness caused by water derived from underground sources. 

After having drilled the well and tapped the subterranean stream, the 
problem seems to be how to bring the water to the surface ; for as a rule the well 
does not flow of its own accord. Deep well pumps of innumerable patterns and 
designs have been constructed, and while each claims to be better than the other, 
they all seem to have their drawbacks. Their capacity is always limited, they 
require power out of all proportion to the work performed, and seem to have a 




FIG. 223. — DR. JULIUS POHLE. 



faculty for getting out of order at the wrong moment; the cause usually being 
'that a rod has been either broken or bent, or a valve or plunger become worn. 
<A11 of this entails endless expense and annoyance, and makes the problem more 
'serious than at first thought. 

When the water level in the well rises within suction reach, a piston pump 
is usually employed ; and while there are a great many good makes on the market, 
the same objection is applicable to them as to the deep-well plunger type, and 
should the water level drop piore than 25 or ?8 feet below th$ surface, they 
become useless. 



596 



USE. 



The problem seems to have been solved, however, by what is known as 
"The Air Lift" system — that is, raising water by means of compressed air. It 
was patented in 1892 by the late Dr. Julius G. Pohle. His process is a novel one, 
because it does away with all moving parts in the well, such as valves, rods, 
plungers, etc. Needless to say, his claim of "simplicity" is borne out and its 
economy and value are attested to by its adoption throughout the country by 
large numbers of Water-works and manufacturing establishments. 

The process consists of placing two properly proportioned pipes in the well, 
one for discharging the water at the surface or tank, and the other for conveying 
the air into the well. These two pipes are connected at the bottom by what is 




FIG. 224. 



-RAISING WATER BY THE POHLE 
NEWARK, 



AIR LIFT 
N. J. 



AT H. LANG CO. S FACTORY, 



commonly known as a foot or end piece, the air pipe being connected at the other 
end to the air compressor. 

The compressed air is then forced through the air pipe into the foot piece 
and water pipe, and by its inherent expansive force, layers or pistons of air are 
formed in the water pipe, which lift and discharge the layers of water through 
the end of the water discharge pipe at the surface or tank. 

At the beginning of the operation, the water surface outside of the pipe 
and the water surface inside of the water pipe are at the same level ; hence the 
vertical pressure per square inch are equal at the submerged end of the pipe, out- 
side and inside. As the compressed air is forced into the lower end of the water 
pipe, it forms alternate layers with the water, so that the pressure per square 



USE. 597 

inch of the column thus made up of air and water, as it rises inside of the water 
pipe, is less than the pressure per square inch outside of the pipe. 

Owing to this difference of pressure, the water flows continually from the 
outside to within the water pipe by gravity force, and its ascent through the pipe 
is free from shock, jar, or noise of any kind. 

These air sections, or strata of compressed air, form water-tight bodies, 
which in their ascent in the act of pumping, permit no "slipping" or back-flow of 
water. As each air stratum progresses upwards to the spout, it expands on its 
way in proportion as the overlying weight of water is diminished by its discharge, 
so that the air action, which may have been, say 50 lbs. per square inch at first, 
will be only 1.74 lbs. when it underlies a water layer of four feet in length at the 
spout, until finally this air section when it lifts up and throws out this four feet 
of water, is of the same tension as the normal atmosphere; thus proving that 
this pump is a perfect expansion engine. 

As the weight of the water outside of the discharge pipe (the head) is one- 
third greater per square inch than the aggregate water sections within the pipe 
when in operation, it follows that the energy due to this one-third greater weight 
is utilized in overcoming the resistance of entry into the pipe, and all the friction 
within it. 

A peculiar and very important feature of the "Air Lift" system is that it 
invariably increases the yield of the well from two to three times. At a recent 
test made by the City of Bethlehem, Pa., the yield of a well which was normally 
at the rate of 20Q gallons per minute, was increased to 627 gallons per minute, 
or just three times, which is something remarkable. 

In breweries it is desirable that the water be at as low a temperature as 
possible, and quite a number have installed Air Lifts because of the fact that the 
water raised by this system has been reduced as much as two degrees in tempera- 
ture. This is ascribed to the expansion of the air abstracting the heat from the 
water with which it is in close contact. 

Prof. Thos. M. Drown of the Lehigh University, some time ago stated 

that the success of filtration is very largely dependent upon aeration. It is 

. claimed that this is accomplished in a great degree by the Pohle system, and is 

no doubt true, as the air sweeping through the water mechanically scrubs and 

cleanses it. 

The value and advantages of Dr. Pohle's system are just becoming known, 
and the day is not far distant when it will be universally adopted : 

Because of its simplicity. 

Because of its economy. 

Because it pumps all the water the well will yield. 

Because of its tendency to increase the yield of the well. 

Because it aerates and purifies the water. 

Because with one compressor any number of wells can be pumped. 

Because it cools the water. 

H. HELLMAN. 



598 USE. 

PUMPING BY AIR. 



An Improved System for Pumping Oil Wells by the Use of Compressed Air, 

The third of a series of patents covering a process for pumping oil vrells has 
just been issued to Mr. M. W. Quick, of Titusville, Pa., and as this system in- 
volves many new features and promises to supplant all other pumping powers, the 
Derrick, has caused an investigation to be made, and is able to present the first 
authentic account of the invention and to furnish those interested in the produc- 
tion of oil with the main points which distinguish the Quick system from all 
others. 

In this system air is compressed to from 14 to 17 pounds initial pressure ; 
conducted through the field in pipes; to the main line, lateral lines run to the 
wells and connect the motors employed in pumping; the utilized air is exhausted 
into a secondary system of pipes which conduct it back to the compressor for 
restoration in its original pressure. The utilized air is thus kept in continuous 
circuit and meteorological changes in the atmosphere are prevented from inter- 
fering with either the compressors or motors. 

The crowning feature in this invention is an automatically actuated valve 
connected with each motor, which regulates the pumping strokes by the quantity 
of fluid pumped. A well that has accumulated a head of oil will be pumped 
with regular strokes at the rate of from 15 to 30 per minute until the fluid is 
exhausted when the pumping motion is suspended, or reduced to a speed so slow 
that the eye cannot detect it, until there is an accumulation of fluid, when the 
regular strokes again pump it off. 

Mr. Quick has also succeeded in bringing the speed of a gas engine under 
automatic control so that it is regulated entirely by the consumption of air in 
operating the wells. An engine so regulated will start up at the rate of say 250 
strokes per minute, provide power for pumping off the wells, and then the in- 
creased pressure will check the engine down to the lowest safe speed or to about 
100 strokes per minute. An engine so regulated responds to the requirements for 
power as readily as does a steam engine with a Fisher governor, and the adjust- 
ment can be made for any desired maximum and minimum speed. 

The advantages claimed for this sytem are many, among the most radical 
of which we present the following as being fully demonstrated in the operation 
of the powers now showing practical results : 

Each well is operated separately and can be run with any desired speed, 
the lifting stroke being with the same rapidity whether the strokes during a given 
time are few or many. 

A given production can be pumped from one well, or from a number of 
wells with the same consumption of central power. 

Each well connected with the system is operated by an individual air motor, 
the strokes of which are automatically regulated by the fluid pumped. 

The requirements for initial power are in perfect harmony with the final 
resulfs obtained. 



USE. 599 

There is no "churning" of the fluid by unnecessary pumping and the forma- 
tion of rod wax is obviated. 

The natural gas pressure ma;y be maintained in wells for the purpose of 
forcing the product into the drill holes. 

By the operation of the motors a pumper is enabled to locate interferences 
with the pumping outfit and decide whether it is leaky tubing, stuck valves, worn 
cups or parted rods. 

The rapid lift and comparatively slow drop permits running sand to settle 
without interference with the working valves. 

Lines for the transmission of power may be buried where they extend 
through towns or cultivated fields. 

Railroad and other crossings, uneven surfaces, precipitous bluflfs and 
streams of water present no obstructions to the transmission of power. 

The system is not interfered with by brush fires, falling trees, ranging cat- 
tle, ice, snow or storms. 

The central poweF plant may be located at any desirable point where it can 
best have attention. 

There are no wearing joints requiring attention and repair. 
There are no distance limits in the transmission and distribution of power. 
Compressed air from the system may be employed in operating field pumps 
for gathering oil, for deliveries to pipe lines or for pumping water. 

The lightest pipe may be employed, old engines changed into efficient com- 
pressors and the materials so employed continued in service indefinitely. 

The wear of cups, working valves and rods is reduced to the lowest possible 
minimum and wells require less roust-about attention. 

A pumper can run a greater number of wells, get along with less tools, use 
less fuel, have little if any expense account and get better production results. 

The system may be installed during any season of the year and in far less 
time than is necessary to put in pull powers. 

At the present time three Quick powers are in successful operation; two on 
properties of the United States Oil Co. at Saint Marys, W. Va., and one on the 
property of the McGraw Oil Co. (in which Mr. Quick is interested, near Tidi- 
oute, Pa.). 

On the property of the McGraw Oil Co., twenty-three wells, covering a field 
about three-fourths of a mile long, are being pumped with a i6 x 12-inch com- 
pressor (made from an old oil well engine) and an expenditure of about six-horse 
power. 

The perfection of this system has occupied the attention of Mr. Quick and 
his associates for more than three years, during which time many additions to the 
junk pile have been made. At the present time, however, it is not known in what 
direction improvements are either possible or desirable. In fact, success far 
beyond anticipations has been the reward for persistent eff^orts, — Oil City Derrick. 



6oo USE. 

PUMPING BY COMPRESSED AIR. 

Pumping water and other liquids by means of compressed air presents an 
attractive field for inventors, and a number have entered it with enthusiasm — 
some with undoubted success, while for the work of others it is yet too early to 
judge it fairly. 

The attractive and most promising traits of compressed air for application 
to this purpose lie in the possibility of transmitting a great amount of energy an 
indefinite distance through small pipes, and then storing it for an indefinite time 
without serious loss; in the convenience, comfort and freedom from danger 
with which it can be applied; and, in some methods, the exceeding simplicity 
and cheapness of the necessary apparatus. One difficulty, not insurmountable, 
but requiring the utmost care in designing and in construction, is leakage of air. 
The other and chief difficulty lies in the loss of much or all of the energy of ex- 
pansion possessed by the compressed air. In some designs there is no pretense 
of utilizing the energy of expansion either through ignorance of the extent of the 
loss incurred or through a desire to make a simple and cheap, and therefore, a 
salable pump. 

We may put all compressed air pumps into one of three classes : 

First. Those that apply the air pressure indirectly through the medium 
of an engine with piston and piston rod exactly as in steam pumps. 

Second. Those that apply the air pressure direct without the intervention 
of a piston, etc. 

Third. Those that lift the liquid by the effect of bubbles liberated in a 
pipe. 

To the first class belong the majority of pumps operated by compressed 
air. It is not the purpose of this paper to discuss that class, but it should be 
said that it is capable of all the variations found in steam pumps, with the one 
drawback that steam has not, viz., freezing when a high rate of expansion is at- 
tempted without reheating. While reheating is desirable to prevent freezing, and 
still more so to economize energy, it adds complication and cost, which must 
seriously retard its introduction in small plants. 

The general action of the second class, direct air pressure pumps, such as 
are now on the market, can be understood by reference to figure I. Suppose the 
vessel submerged and filled with water. Now, if compressed air enters through 
the pipe C, the water will be driven out through the pipe A. When the vessel is 
thus emptied, .a mechanism operated by a float will close the compressed air inlet 
and open an outlet so that the compressed air will escape into the atmosphere. 
As the air thus escapes, water will rise through the valve D, and refill the vessel. 
When the vessel is thus refilled, the compressed air inlet will again be opened 
and the outlet closed by some mechanism operated by a float, thus making the 
whole action automatic. Such pumps can be made of simple construction, with 
reasonable certainty of action and at moderate cost. 

All these merits are apparent or can be easily demonstrated to a would-be 
purchaser ; but the fault in such a pump is not so apparent nor so easily demon- 
strated. Moreover, the agent will be sure not to allude to it. This fault is the 
loss of all the energy of expansion. To show how serious is this loss the table 
below is inserted, showing the maximum theoretic efficiency for such pumps at 



USE. 



6oi 



different heights of lift. Of this, not more than two-thirds, or at most, three- 
fourths, can be realized in practice. 



Height in feet 

to which water 

is lifted. 



Maximum theoretic 

efficiency of air used 

without expansion. 



34 
68 

102 
170 
238 
306 



.0.72 
,0.61 
.0.54 
.0.46 
.0.42 
.0.39 



It will be noticed that the efficiency of such pumps decreases rapidly as the 
lift increases; hence we may be justified in using such for low lifts where it would 
be folly to apply them to high lifts. There is a legitimate field for such pumps. 




KIG. 225. — DIRECT AIR PRESSURE PUMP. 



but we should know its limit and keep them within it. In justice to such pumps 
it should be said that they can and should be more efficient, as well as more dura- 
ble, -than the non-expansive piston pump. 

Inventors have attempted to make a direct air-pressure pump that will 
utilize the expansive energy of the air. The writer has discovered in the United 
States two patents for such (Nos. 474,388 and 139,538). In both, the complicated 
and imperfect mechanical details bar all possibility of success. However, the 
main idea — the same in both — is correct, and, in the writer's opinion, capable 
of being carried out sucessfully. This idea is to have two vessels of the general 
nature of that shown in Fig. 225, and instead of allowing the compressed air to 
escape into the free atmosphere, it is, after the vessel is emptied, conducted back 
through the compressor and into the other vessel; thus using the same air over 
, and over again, one vessel filling with water while the other is emptying. By 



6o2 



USE. 



(his means it will be seen at once that none of the energy of expansion of the 
air is lost. The problem, then, remains to make the details simple, economical 
and sure of action. The problem is interesting from both a mechanical and an 
economical point of view. It also offers a good opportunity for "mathematical 
gymnastics." 

We will now consider briefly the third class, in which water is raised by 
the effect of bubbles liberated in a vertical pipe. This has recently come to be 
known as the "Air Lift Pump," which name was given it by the "Engineering 
News' in an article of June 8th, 1893. (The article gives a very complete his- 
tory of the air lift pump). 

In construction it is the simplest of all pumps, the only essential being an 
open pipe, set approximately vertical with its lower end submerged, and some 
means of injecting air into the pipe below water-line. Each bubble of air 




FIG. 226. — CHAIN AND BUTTON PUMP. 



liberated within the pipe, by virtue of its buoyancy, exerts a certain force upward, 
tending to lift the column of water within the pipe. It is the accumulated lifting 
force of a number of bubbles that produces the action of the air lift pump. From 
this point of view the general principle of the action is easily comprehended, but a 
mathematical analysis of its action with a view to determining best pro- 
portion, is by no means simple.* Indeed, the difficulties are such that prob- 
ably experiment alone will determine what are the best relations between 
depth of submersion, height of lift, volume of water discharge, volume of air 
used, area of discharge pipe, etc. 

In this kind of pump, as in others, a large percentage of the energy put 
into the system may be lost through neglect of proper proportions and adjust- 
ments. A considerable proportion of the energy will always be lost by the bub- 
ble slipping through the surrounding waters, whether the whole be ascending 

• See '♦ Theory of the Air Lift Pump," Journal of the Franklin Institute, July, 1895. 



.■■Br V.'J"->.' . '■'' 



USE. 603 

or not. In this respect the air lift pump is very similar to the well-known "chain 
and button" pump as commonly used for lifting water from cisterns. In the lat- 
ter we know that if the motion of the chain is too slow, all the water will slip 
by the buttons and remain in the cistern. So in the former: if the bubbles are 
too few or too small, or the lift too great, no water can be brought up. The 
difficulty lies in that the rubber buttons in the one case, and the bubbles of air in 
the other, do not make water-tight pistons. A bubble cannot be made to occupy 
the full cross section of a pipe under circumstances in which the air lift pump 
must act. 

The writer is aware that a patent has been allowed for an air lift pump 
in which the claim is made that the bubble does fill the whole cross section of 
pipe, and that therefore they act as pipe-fitting pistons. The same claim is re- 
iterated with great stress in all the literature on the subject issued by agents 
for said patent. If this claim can be realized for a series of bubbles, it can be 
realized with a single one. Does any one think it possible to make a single bub- 
ble remain stationary in a pipe under the given conditions? Or will it be claimed 
that when an air lift pump is in action and the air supply is suddenly cut off, 
that the "pipe-fitting pistons" of air will stand still in the pipe? Such must be 
the result if the claim is correct. Common sense, experience and science all op- 
pose this claim. Let the advocates of the claim devise an experiment to prove it. 

ELMO G. HARRIS. 



Experiments with a glass tube, applied in the manner of the Air Lift 
Pump, will show clearly defined piston like sections of air and water, the dis- 
charge of air and water being intermittent and almost uniformly regular. When 
air is first admitted to the pump the water in the pipe above the point of air ad- 
mission is blown out in a solid stream, as the shot is discharged from a gun. ■ 

If this is true, why may we not expect that the succeeding volumes of 
water which, through the head, are able to get above the air jet, are discharged 
in the same way? There is a continuous struggle going on between air and water 
tc get into the eduction pipe, and notwithstanding the fact that air is admitted in a 
continuous stream, its admission is not continuous, because the water at times 
practically shuts it off. These interruptions are, however, of very short duration. 

The secret of the Air Lift Pump action is in the high velocity with which 
the air and water are discharged through the eduction pipe. Without this high 
velocity there would be no piston like sections except perhaps in a small glass 
tube model where capillary attraction takes the place of velocity. 

Let us imagine a case where the eduction pipe is ten feet in diameter, and 
admit air— say through an 8-inch pipe— to a Pohle foot piece, there will be noth- 
ing but bubbling of air up through the water and no piston like sections will be 
formed ; but let us suppose that this air pipe is 5 or 6 ft. in diameter and that it 
has a free discharge under several atmospheres, is it not easy to understand, that 
under such conditions, the air might occupy the entire section of pipe and that it 
might discharge the water like a gun shot? Is it not also easy to understand that 
there will be a high velocity of movement excited upward through the eduction 
pipe, and that we will either have a discharge of air alone, a discharge of water 
alone, or an intermittent discharge of both? This intermittent action takes place 



6o4 USE. 

provided the air pressure at the foot piece is about equal to the water pressure due 
ic its head. The two must be almost completely balanced, and it is because of a 
conflict for supremacy or a change of pressure between air and water, which goes 
on at all times, that the piston like sections are formed. If it is admitted that these 
sections are formed at any time and that the velocity of movement upward is 
great, it is not difficult to understand the Pohle Pump exactly as Dr. Pohle 
invented and patented it. 



PUMPING BY COMPRESSED AIR.* 



BY E. A. RIX. 



My object in this paper is not so much to enter into an elaborate descrip- 
tion of the various methods of compressed air pumping, as to touch on points 
which seem to have been heretofore neglected by those who have written on the 
subject, to suggest some new methods and to encourage, if possible in the build- 
ing of pumping machinery, to design something specially adapted for the use of 
compressed air. 

Compressed air has been handicapped from the very beginning in the 
matter of pumping, because it has been used with stock pumps which have been 
designed in general for boiler feeding and tank purposes, and no particular 
regard has been paid to the matter of cylinder proportions and appropriate pres- 
sures. Compressed air users in the same manner have been obliged to utilize 
old steam motors of all kinds, the general assumption being that steam motors 
are equally adapted for the use of compressed air. I will plead guilty to having 
committed this error on many occasions, and the remarkably poor efficiencies 
which I have obtained have led me to investigate the matter and to become a firm 
advocate for the designing of special motors for compressed air machinery. 
Great attention is paid to the designing of motors for the use of steam, even to 
the very smallest detail, and yet compressed air, which is almost doubly as expen- 
sive as steam to produce, has been compelled to take any misfit for its use, and it 
has been condemned right and left for lack of economy, and has had a difficult 
time to maintain its proper existence in the face of the results it has produced in 
many cases with motors which were designed for something entirely different. 

Those who arc informed on the subject arc perfectly well aware that steam 
and compressed air, while following in general the laws of perfect gases, are not 
similar enough in their phenomena to be used in the same motor, the general 
difference being that for similar terminal pressures the points of cut off are 
different. Air, also, does not condense, which permits unlimited multiple re- 
heating. 

There has been sufficient development made in the line of air compressors, 
so that now the attention of manufacturers should be turned to the constructing 
of economical air motors ; and among the first to inaugurate this reform should 
be the pump builders, for pumps, as ordinarily furnished for compressed air, have 

•Paper reaxl before the Technical Society of San Francisco. 



USE. 



605 



the poorest economy of any compressed air machinery, not even excepting a rock 
drill. 

It is not necessary to revolutionize shop methods nor to carry an expensive 
stock of specially designed pumps in order to accomplish the results desired. It 
seems to me that merely pointing out to an intelligent customer the fact that his 
pocket will be vastly benefited by having a pump specially constructed for his 
work will be a great help at the moment ,and as soon as it becomes generally 
known that great advantages are to be gained thereby, many people will abandon 
the old methods and the reform will be inaugurated. 

I shall endeavor in this paper to point out some economical methods of 
pumping water by compressed air, and to suggest how others might be accom- 
plished. Let us consider generally the various methods used to lift water by 
compressed air, and compare them in such a manner that those interested may 
better understand the subject, thus enabling them to improve upon these methods 
when occasion offers. It is discouraging to those who believe that compressed 

TABLE 51. 
FOR 100 GALLONS PER MINUTE. 200 FEET HIGH. 



No. 1. 


No. 2. 




No 


3. 






>>'^ 






>> 


i^.ti 






>i 


t>,-t5 






t^ 


°25s3 


•S<5 


g-nS 


di 


S 


^< 




Q^ 


^ 


^< 


?rS 


Oh' 


S 


Ratio 
Air 
Wat 

Cylin 


II 




s <c 
^1 


W 


'5 


§2 


'4 


SG 






11 


cii 




1-1 


134 


11.0 


29 


17^ 


















1.5-1 


153 


48.8 


21 


24 
















. 


1.75-1 


169 


36.6 


19.5 


25 


















2-1 


181 


27.5 


16.2 


30 


130 


50 


18.2 


27 


170 


50 


23.8 


21 


2.25-1 


197 


22 


15 


33 


















25-1 


206 


17.6 


13.5 


37 


137 


40 


16.4 


30 


178 


40 


21.5 


23 


3-1 










145 


33 


15.2 


33 


180 


33 


19 


26 


3.5-1 










152 


29 


15 


33 


185 


29 


18.5 


27 


4-1 










158 


25 


13.5 


87 


205 


25 


17 


28 


5-1 










176 


20 


12 


41.5 


225 


20 


14.7 


34 



air occupies an economical as well as a useful field to see the various tables, rules 
and computations offered to the public for calculating the amount of air required 
to lift, water, without a word of explanation that might temper the almost 
general conclusion that compressed air is a very expensive luxury. It would 
require a stout heart and a long purse to put in a compressed air pumping plant if 
the verdict of the various quantity tables were final. One consulting these 
authorities, would invariably conclude that the efficiencies were so low that only 
pressing necessity would decide in favor of compressed air. 

The percentage of efficiency credited to compressed air in these tables 
ranges from 15 to 30 per cent. No mention is made of possibilities beyond these 
numbers, and one is left but the one conclusion— that from four to seven horse 
power must be furnished to the compressor in order to produce a net yield of 



6o6 USE. 

one horse power in water pumped, and particularly is this discouraging when 
enterprising advocates of electricity keep emblazoned before us all that imposing 
array of efficiencies that seem to almost jostle the revered lOO per cent, from its 
pedestal. Moreover, all this is misleading besides, for there are efficiencies to 
be obtained in the proper use of compressed air in pumps that are more than 
satisfactory, that in fact are difficult to exceed in many instances, and I have 
tried to make it clear in this paper how to practically realize these results. 

As an example of the information given by some of the catalogues pub- 
lished by builders of compressed air machinery, take an example of one hundred 
gallons of water pumped two hundred feet high. What is the quantity of free 
air and the pressure required in direct-acting pumps? Reference is made to the 
table (51), containing extracts from three publications. One hundred gallons 
per minute, raised 200 feet high, requires, theoretically, 5 horse power. Com- 
paring this with the table, we find that the efficiencies range from 17 to 40 
per cent., the pressure from no to 20 pounds, the volumes from 225 to 130 cubic 
feet of free air per minute, and the cylinder ratios from i to i to 5 to i. It will 
also be noted that the pressures required for the same cylinder ratios vary 150 
per cent. The air pressures given are all receiver pressures, or pressures in the 
main air pipe, which fact is not mentioned, leaving one to draw the conclusion 
that, no matter what the pressure in the main is, it is only necessary to install a 
pump with a large cylinder ratio and use low pressures. 

Compressed air in mining is used for driving rock drills, for hoisting and 
pumping, and the average pressures carried in the mains correspond very nearly 
to the steam pressures formerly used for the same work, and 90 pounds gauge, 
independent of altitude, seems to be the standard pressure. This being the case, 
these tables and pumping data should all be calculated from some such standard 
basis, with proper co-efficients for variations from the standard pressure, and a 
table giving the proper cylinder ratios, for different heads, using the standard 
pressures as a basis, would, it seems to me, be more helpful to those who wish 
to consult tables for guidance. 

In this paper we shall assume 90 pounds to be the standard pressure car- 
ried in the mains and that it takes 20 brake horse power to compress 100 cubic 
feet of free air per minute to that pressure at sea level with a single stage ma- 
chine. This is more than is called for by the catalogues, but observations from a 
great many compressors, of many makes, justify me in this statement, and pres- 
sures all along the line will follow the same rule. 

There appear to be six general forms of compressed air pumps : 

First — Displacement pumps for full pressure only. 

Second — Displacement pumps using expansion. 

Third — Direct acting pumps for full pressure only. 

Fourth — Direct acting pumps using expansion. 

Fifth— Air lift pumps, single and combined with displacement chambers. 

Sixth— Pumps operated by independent motors. 

The notations employed will be gauge pressures, unless otherwise specified. 
Temperatures are expressed in Fahrenheit degrees. The altitude is at zero; that 
is to say, sea level, and the atmospheric pressure is rated at 13 pound? for the 



USE. 



607 



sake of convenience, and one gallon of water, which equals .134 cubic feet, raised 
one foot high, is the unit of work to be performed. 

The first general system of pumps, as before classified, viz., displacement 
pumps for full pressure only, appear to be the simplest of all, and are those which 
would naturally be first suggested to the mind. If we have a closed vessel con- 
taining water, having a discharge pipe, let us say 210 feet high, connected to its 
bottom, and if we force air at 90 pounds pressure slowly into this vessel, the air 
will rise to the top of the vessel and water will be discharged exactly equal in 
volume to the volume of air forced in, and (gox.o68) + i, or 7, will represent 



Automatic Valve 




FIG. 227. 



the number of cubic feet of free air required to raise each cubic foot of water. 
Inasmuch as practice will require a certain additional pressure to give a dynamic 
head, and as there is a certain amount of pipe friction to overcome, and as some 
air also is absorbed by the water, the number 7, before stated, can properly be 
made 9 cubic feet of free air used to i cubic foot of water pumped, or, expressed 
in foot gallons: i cubic foot of free air at 90 pounds will perform i/9x2io-.i34 = 
17s foot gallons. The i cubic foot of free air has received 1/5 horse power, or 
6,600 foot pounds of work expended upon it. 175 foot gallons = 175x8.3 pounds, 
the weight of I gallon = 1,452 foot pounds, or an efficiency of practically 22 per 



6o8 



USE. 



cent., and it will be observed later on that this is better than most ordinary direct 
acting pumps will do with cold air as ordinarily used. 

The efficiency of this system may be increased 15 per cent, by compound 
compression, or, if the water to be pumped has a higher temperature than the air, 
as, for instance, in the Comstock, where the water is 120 degrees, the absolute 
temperature would be 580 degrees, and the efficiency would then be 22 x 580-520 
= 24.5 per cent. Assuming, for this illustration, that the Comstock is at sea 
level, the air in this system of pumping may be likened to a flexible plunger hav- 
ing I square foot area, making one stroke per minute, and the actual length of 
stroke equal to the number of cubic feet of compressed air furnished per minute, 
diminished by the absorption, leakage, clearance and equivalent quantity necessary 



Switch^ ^ 
Automatic 



Air _ 




L 





Water 


r 


rt— * 







JJ Compressor 




Pump Tatiks 



iOpeu Well, Lake 
Spring^ River or 
Mine Svmp. 

FIG. 




Tanks will be proportioned 
according to capacity of wells . 



228. 



to furnish dynamic head and friction and increased or diminished by the ratio 
of absolute temperature of air and water. It would be proper to range the effi- 
ciency from 15 to 22 per cent. The chambers of this pump must be submerged, 
which limits its usefulness. In a sump, or tank, in a mine, and for lifts within 
range of ordinary compressors, say up to 250 feet, it will still probably exceed 
the efficiency pounding of this system, however, will be of the ordinary direct 
acting pump. 

One can readily see that it exhausts its chambers into the atmosphere at 
full pressure, and all the expansive work contained in the air is lost. A proper 
compressor, suggested later on, which will utilize some of this expansion and 
increase the efficiency materially. Without reflecting, perhaps, engineers have 
generally discarded this system a>s too primitive and uneconomical, whereas, in 
fact, in many instances, it is cheaper by far to install, and often would e^^ceed 



USE. 



609 



the efficiency of a direct-acting pump. For handling sewage, or material which 
would obstruct or destroy pump valves, its utility gives it a desirable place, but 
over and beyond this a well-constructed pump of this type has a right to be 
properly considered in comparison with ordinary direct acting pumps. In the 
pumps of this type there are generally two chambers, so that while one is filling, 
the other may discharge, and thus insure a steady delivery, but frequently single 
vessels are found adequate, and in some cases prove to be the proper installation. 
The diagram, Fig. 227, gives a general idea of this type of pump. 

As may be imagined, the inlet and outlet of the compressed air in the 
original pumps of this class were controlled by floats, which are unreliable and 
limit to a great extent the size and shape of the vessels, and the clearance was 
excessive. The modern type, however, has eliminated all of these uncertainties, 
and the pump of the Merrill Pneumatic Pump Co. has a differential controlling 
valve, situated above the chambers, and this valve is automatic and positive, and 
the chambers are free from, floats. A large number are in use, and being free 
from many complications which exist in ordinary pumps, they may be classed 



Switch, 
Automatic 
Air «— 




J 



J} Compressor 



Water 



JU 



Water 



m 



r 



let /'o=Hig'hest pressure. 

^:>=Lowe8t " 

F="Volnnie of tank. 

a= " " air pipe. 

?-=EflFective etroke volume of 
compressor 

M==Number of strokes to re- 
duce pressure from Fo 
top. 

log Po~ log p 



^og(v+a- 



logCFf a) 



NOTES ON OPBBATION. 

One tank (or group of tanks) is emptied 
by air pressure while tlie other is drawn 
full by suction, the air charge being so ad- 
justed that one tank is drawn full of water 
just when the other is emptied. 

THE SWITCH 

Can be automatically operated in either of 
three ways : 

1. By means of the suction in the intake to 

compressor which depends on the 
height to which water must be drawn 
in filling the tanks. 

2. By a mechanism that will throw the 

Switch at a given number of compres- 
sor strokes — the number required be- 
ing that which will empty one tank 
and fill the other. 

3. By an electrically controlled mechanism, 

the circuit being controlled either by 
fioats in the pump tanks or by a pres- 
sure gauge on the in-take pipe. 

ADVANTAGES. 

1. The expensive energy in the compressed 

air is fully utilized. 

2. There are no moving or delicate parts 

outside the compressor room except 
the check valves on water pipes. 

3. One compressor can pump water from 

any number of sources. 

4. In mine drainage the tanks may be sub- 

merged to any depth. 



FIG. 229. 



alongside of ordinary direct acting pumps, where submersion is possible. There 
is no reason why lifts in two or more stages would not be entirely feasible with 
this pump. 

Class No. 2 consists of displacement pumps using more or less expansion. 
This class of pumps is best exemplified by the Harris system, owned and operated 
by the Pneumatic Engineering Co., of New York, and this system is extremely 
interesting simple and economical, and I have no doubt, would prove satisfactory 



6io 

in many cases, especially in mines having a steady flow of water at reasonable 
heads to be handled. 

This system consists in displacing and elevating the water precisely the 
same as in Class i, with the difference that while in Class i the water is imme- 
diately exhausted from the water vessels into the atmosphere and all its energy 
of expansion lost, the compressed air in the latter system is allowed to do work 
in expanding against the compressor piston and thus, theoretically speaking, all 
its expansive energy is saved, but practically the manufacturers claim the losses in 
leakage and friction to be about 15 per cent., a statement which deserves credence. 

The action of the pump is as follows: There are two chambers placed 
within suction limit of the sump, or submerged, as desired. An air pipe leads 
from the compressor to the top of each chamber. There is a single water dis- 
charge connected to both chambers, and a single suction. The system is so 
arranged that while one chamber is filling the other empties, and an automatic 
switch plays the important part of regulating the entrance and exit of the air. 
The system is a closed one, and only leakage is replaced automatically. 

Suppose one of the chambers filled with water; the air is then admitted 
at such pressure that the water is expelled and the air pipe and chamber are full 
of compressed air at the pressure of the water lift, or slightly more. The other 
tank has in the mean time filled with water. At this point the automatic switch 
connects the air pipe of the empty chamber with the intake of the air cylinder and 
the air pipe of the other chamber with the discharge of the compressor cylinder. 
It is evident that instantly the air in the first chamber will expand, through the 
compressor and equalize the pressure in the empty air pipe of the second chamber 
and all clearances. This part of the expansion is lost, but it amounts to but 
little. The compressor now transfers the air from the first chamber to the second, 
displacing the water in tht second, and the air from the first chamber thus does 
work upon the air compressor piston in expanding from full pressure to zero. 
When zero pressure is reached in the first chamber, if it is not submerged, the 
compressor continues to draw air from it until the water rises and fills it. At 
this point the first chamber is ready to be discharged, but if there has been leak- 
age the second chamber has not received enough air to complete its discharge, 
and this is now supplied by a check valve in. the intake pipe, which is set to open 
at a suction pressure slightly above that necessary to draw the water into the 
chambers. If the chambers are submerged, an ordinary check valve will auto- 
matically supply any deficiency in the quantity of air. The second chamber, being 
completely discharged, the automatic switch reverses and the cycle is complete. 
Of course, everything depends upon the reliability of the switch, which is placed 
on the air pipes near the compressor, where the engineer can see its operation and 
adjust It if necessary. It can be automatically operated in three ways: First, by 
means of the suction which occurs in the intake pipe to the compressor when the 
water is drawn above its outside level in one of the chambers; second, by a 
mechanism that will throw the switch at some assigned number of strokes of the 
compressor, the proper number being that which will empty one chamber and 
hll the other; third, by an electrically controlled mechanism, the circuit being 
made and broken by a pressure gauge on the intake of the compressor, or by a 
float in one of the chambers. - ■ 



USE. 6ii 

In Figs. 228, 229 and 232 we have diagrams and data supplied me by the 
Pneumatic Engineering Co., which will be interesting to those wha care to in- 
vestigate this extremely interesting and economical method of pumping by com- 
pressed air. 

Fig. 231 gives a problem of pumping under 90 pounds pressure which shows 
in detail the range of the work on the air compressor piston during the progress 
of changing the air from one water chamber to the other. It will be noted that 
the net work is even less than the full pressure work at 90 pounds pressure, thus 
showing that the compression work is practically eliminated, and 90 pounds pres- 
sure can be transferred from one receiver to the other at less than one-third of 
the power required to fill a receiver at 90 pounds pressure, consequently this sys- 
tem should be at least twice as economical as the regular displacement system. 
The disadvantage is that it requires an independent plant and a double set of air 
pipes. I have no hesitancy in placing the efficiency at from sixty to seventy per 
cent., and consider it a very desirable system for mine station pumping. 

DIRECT ACTING PUMPS. 

The ordinary direct acting pump is the best known of all power pumps, 
and is the typical example of a motor driven, displacement pump. Its efficiency 
suffers on account of its large clearance, its apparent inability to realize full stroke 
and the ill-advised selection of cylinder proportions. In general it is given a 
mechanical efficiency of 65 per cent. It is not an absolutely complete displacement 
pump, because the valves are generally arranged to cut off just before the com- 
pletion of the stroke in order to exhaust the inertia of the moving parts by the 
time the stroke is finished, and this gives a slight expansion in the cylinder, but 
this may be neglected in general and the pump put in the displacement class. 

If a pump uses full pressure only, it is evident that the more full pressure 
a compressor diagram shows, the greater will be the efficiency of the system. The 
lower the air pressure the less the compression work and the greater the pro- 
portion of full pressure work, consequently the lower the pressure the more 
efficient the system. This really refers to the compressor and not to the pump, 
for the pump works the same whether it receives air at 10 pounds pressure from 
the compressor or whether it has been expanded from a receiver having a higher 
pressure, provided the temperatures are constant. If we look for the best effi- 
ciency then from direct acting pumps we must put in an independent compressed 
air system and carry a low pressure. We can hardly imagine that this would 
be generally done, and consequently we must count on the standard pressure of 
about 90 pounds for our economies and proportions. 

After comparing the various tables of compressed air quantities for direct 
acting pumps, it appears that the calculations of William Cox are most reliable, 
and they agree very nearly with practical results that I have noted. He, how- 
ever, like the others, considers that the pressure used by the pump is receiver 
pressure. His principal formulae are as follows, based on 100 feet per minute 
of piston speed. Other speeds will naturally be in proportion. 

Diameter water cylinder = .54 gallons raised. 

(Diameter air cylinder) 2 = .5 x head x (Diameter of water cylinder) 
2 X gauge pressure. 



6l2 



USE. 



Volume of free air = .63 x (Diameter of air cylinder) 2 x (i + .068 
gauge pressure) and, in general, without regard to any factors but quantity, head 
and pressure, we have the volume of free air = .093 foot gallons gauge pressure 
X (i + .068 gauge pressure). 

In using these it must always be borne in mind that the pressures given 
are receiver pressures; that is to say, that the compressor furnishes air to the 
mains at pressures called for in the tables, and if any higher pressures are car- 
ried in the mains, such as 90 pounds, and if then the air cylinder of the pump 
is so large that the air is wiredrawn to it, then the quantities of compressed air 
given should be multiplied by a constant, such as given in Column 6, Table 52, 
when the pipes are short between the main and the pump, as occurs generally 
in a shaft. 

The constants in Column 6 are simply about 70 per cent, of the ratio of 
the absolute temperatures due to the expansion of the air from 90 pounds to the 
pressures indicated in the tables, and the horse power will not be the power 
required to raise the pressure from atmosphere to the working pressure, but 
always that required to deliver it into the mains. This fact makes sorry work 
for efficiencies. 

Inasmuch as most pumps are in the shaft near the main, a very short pipe 
connects them to the main, and the air is expanded through this short pipe to 
the pump, for pressures less than that in the main. This expansion reduces 
the temperature of the air entering the pump to quite a marked degree. Not by 
the theoretical amount due to the pressure drop, for some heat from external 
sources can be supplied, and wiredrawing furnishes a disputed amount also. 
While I have made no experiments on this subject, I have assumed that less 
heat would be given to this expanding air than a good water jacket would take 
out of the air during compression, and I have assumed the temperature to drop 
70 per cent, of that, due to the pressure drop. This reduces the air volume and 
adds to the quantity consumed by the pump and consequently lowers its efficiency. 

It would be good practice to let this cold air gain normal temperature 
before reaching the pump cylinder, which can be done by passing the water 
being pumped into an enlargement in the discharge pipe within which is a coil 
through which the air is passed, but if no such device is used and the air pres- 
sure in the mains is 90 pounds, we shall find that the table (Table 52), expresses 
about the real condition of affairs for a pumping effort of 10,000 foot gallons. 

In explanation of the table: 

10,000 foot gallons = 83,000 foot pounds = 2.5 horse power, theoretical. 

Column I— Gauge pressures in air cylinder of pump. 

Column 2— Volume of free air required, calculated from Cox's com- 
puter, No. 76. 

Column 3— Horse power corresponding to above volume, calculated from 
same computer. 

Column 4— Ratio of the gauge pressures in Column i to 90 pounds, 
standard mining pressure. 

Column 5— Adiabatic temperature ratios corresponding to the pressure 
ratios in Column 4. 



USE. 



613 



Column 6 — Gives the practical temperatures, ratios being 70 per cent, of 5. 

Column 7 — Is Column 2 multiplied by Column 6. 

Column 8 — Horse power calculated for Column 7 by Cox's computer, 
No. y6. 

Column 9 — Percentages of Column 3. 

Column 10 — Percentages of Column 8. 

Conclusions from table: 

First — The lower the air pressure in the main, with cylinders designed 
properly, the greater the efficiency, reaching as high as 30 per cent. 

TABLE 52. 



Ill 


2 


3 


4 


5 


6 


7 


8 


9 


10 


< 



i 





i 


1 


.2 


6 



^1 


i 
g 

Ph' 


5 




0^ 





w 


^^ 




5 





w 


§ 




20 


113 


8.4 


3 


1-37 


1-26 


142 


28.5 


30 


9 


25 


103 


9 


2.6 


1-32 


1-22 


125 


25 


27 


10 


30 


97 


9.6 


2.3 


1-27 


1-19 


115 


23 


26 


11 


35 


93 


10.1 


2.1 


1-24 


1-17 


108 


21.5 


25 


11.5 


40 


89 


10.6 


1.9 


1-2 


1-14 


101 


20 


24 


12.5 


45 


87 


11.3 


1.7 


1-16 


1-12 


97 


19.7 


22 


12.6 


50 


85 


1?.0 


1.6 


1-14 


1-11 


94 


19.1 


20.5 


13 


55 


82 


12.5 


1.5 


1-12 


1-09 


89 


18 


20 


14 


60 


80 


12.6 


1.4 


1-10 


1-07 


85 


17 


19.8 


14.7 


65 


79 


13 


1.31 


1-07 


1-06 


84 


16.8 


19.3 


15 


70 


78 


13.4 


1.24 


1-06 


1-05 


82 


16.4 


19 


15.3 


75 


77 


13.6 


1.17 


1-05 


1-0 1 


80 


16 


18.5 


15.6 


80 


76 


14 


1.1 


1-04 


1-03 


78 


15.6 


18 


16 


85 


75 


14.5 


1.05 


1-02 


1-02 


76 


15.2 


17.5 


16.5 


90 


74 


14.8 


1 


1-0 


1-0 


74 


14.8 


17 


17 



10,000 foot-gals. = 83,000 foot-lbs. = 2.5 H. P. theoretical. 

EXPLANATION OF TABLE. 
Col. I — Gauge pressures in air cyl. of pump. 

Col. 2 — Is the volume of free air required, calculated from Cox's computer. 
Col. 3 — Horse power corresponding to above volume, calculated from same 

computer. 
Col. 4— Ratio of Gauge pressures in Col. i to 90 lbs. Standard Mining Pressure. 
Col. 5 — Adiabatic temperature. Ratios corresponding to pressure ratios in No. 4. 
Col. 6 — Are practical temperature ratios, being 70% of No. 5. 
Col. 7 — Is Col. 2 multiplied by Col. 6. 

Col. 8— Is H. P. calculated for No. 7 by Cox's computer 76. 
Col. 9— Are percentages of Col. 3. 
Col. 10 — Are percentages of Col. 8. 



6i4 



USE; 



Second-The efficiency drops immediately if the air is expanded through 
the throttle into an air cylinder which requires less pressure than the main. 

Third— At standard mining pressure of go pounds the efficiency is about 
17 per cent, with properly designed cylinders, and probably drops as low as 12Y2 
per cent, in pumps where "just one turn of the valve is open." 

Fourth— Very little loss occurs in using pressures within 10 per cent, of 
the pressure in the main, which is ample to impart proper dynamic head to the 

pump. • • J 

If compound compression should be used, then the efficiencies mentioned 
can be increased 15 per cent., and they will range then as high as 34.5 per cent, 
for low pressures, and from 19-55 to 14.5 for standard mining pressures. 

If the air is reheated, so that the pump cylinder receives it at 300 degrees 
Fahrenheit, and if no account is made of the cost of reheating, then the effi- 
ciencies for low pressure and simple compression will be 42 per cent., and com- 



/ 

^^^ Area 18.60 
^^.....'-''^^^ Atmosphere 




[ 

1 

1 


i 

Pi 

i 

1 










, r." J 


z_.c 


i_ 


> 



FIG. 230. — DIAGRAM OF ORDINARY DIRECT- ACTING PUMP. 



pound compression 48 per cent., and for standard mining pressures, for simple 
compression, 24 to 17.5 per cent., and for compound compression, 27^/^ to 20 
per cent. 

According to the above table, at standard mining pressure the efficiency, 
using cold air, is 17 per cent, at maximum. According to our statement, if 
20 horse power produce 100 cubic feet of free air per minute compressed to 90 
pounds, I cubic foot will cost 6,600 foot pounds of work. Seventeen per cent, of 
this would be 1,122 foot pounds of useful work that the one cubic foot of free 
air would perform; 1,122 foot pounds is 135 foot gallons. 

I have measured the exhaust of many pumps using air at from 80 to 90 
pounds, and I have found their work to be approximately 135 foot gallons for 
each cubic foot of air, and I have used this figure in all my calculations for 
ordinary pumps, properly proportioned. Thus, to lift 200 gallons a minute 200 
feet high, would be 40,000 foot gallons. This, divided by 135, would require 300 
cubic feet of free air compressed to 90 pounds, which in turn requires 3 x 20, 
or 60 horse power to produce it. If compound compression be used, I increase 



USE. 615 

the 135 foot gallons by 15 per cent, and call it 15S foot gallons, and if reheating 
is used, in either case, I increase the 135 by the ratio of absolute temperature 
which I am satisfied the pump receives. 

The efficiency of the direct acting pump is seen from diagram 230, as 
follows : 

With a simple compressor the M. E. P. of compression is a little more than 

/ the M. E. P. adiabatic, say, 40 pounds. This corresponds to an area on this card 

; of M. E. P. = Area x Spring Length of Card 40 = A x 15-7, or 280-15 
= 18.66 square inches. The adiabatic volume of G, B, D, H shrinks to A, B, 
D, C before arriving at the pump. The pump having a mechanical efficiency of- 
65 per cent., the volume i B, F, E is all that really does useful work. That 
area is .60 x 6 = 3.60 square inches, and 3.60-18.66 = 19 per cent., which com- 
pares nearly with our other figures. 

We found simple displacement pumps. Class I, giving 175 foot gallons of 
work, and direct acting pumps. Class II, giving 135 foot gallons of work. .This 
might be anticipated, because in Class I the air is used isothermally throughout, 
the pressure is always exactly what is necessary and clearance is small and no 
mechanical movements to overcome. 

Referring again to Table 52, and remembering that we have assumed 
90 pounds as our standard pressure in the mains, we note how serious a loss we 
would entertain if we used a pump having such a large air cylinder that the 
working pressure was only 20 pounds. One not skilled might expect to get 30 
per cent, efficiency, but he would really get about 10 per cent., or just .300 per 
cent, out of the way, and this justifies the remark that I have heretofore made 

I that these catalogue tables are misleading. Except for extremely small quantities 
and for sinking pumps, I cannot, justify the use of simple, direct acting pumps 

I for compressed air service. 

Simple displacement pumps, mentioned in Class I, can be made to use the 
air with at least partial expansion, and I suggest the following for consideration 
and experiment. It is new to me, and occurred to me while searching for a 
cheap and economical means to do some air pumping. We will take the same 
problem of work at 90 pounds pressure, and, in order to make the problem 
simple, I have made it purely theoretical, and we can supply whatever efficiency 
coefficient we deem appropriate. 



THE COMPOUND DIRECT-AIR-PRESSURE PUMP WITH ADJUSTING 

RECEIVER. 



Computations for Proportioning the Parts and a Graphical Presentation of one 

Cycle of Operation. 



SYMBOLS AND NUMERICAL VALUES. 



-P' = Absolute Maximum pressure in lower tank. 
P"= " «' " '< upper " 

P' and P= " Minimum " " either " 



V'= 

V"= 
R= 



6i6 USE. 

a'= Volume of air pipe to lower tank. 
" " upper " 

" "lower " 

" "upper " 

" " Keceiver. 

compressor stroke. 
7i=Number of compressor strokes. 
Pw= Variable pressure in tanks. 
W= ' ' work per stroke. 
Vn= ** water volume delivered per stroke. 

FORMULAS. 

P'{v'+a')+p" a"-p' a' _ n J 

^ ~ P' 

_ P' {v"+a")— P' ('i)' -\-a')-^p' a'—p" a" jj 

^= F^P^^ 

p,^p,('4i^\^ ///. 

Po=imtial pressure, Pn tliat after in strokes. 

lA)g. Po-log. Pn jy 

log. {v-^a-\-v)—tog. {v-\-a) ". 

^,^P,,%_^ F. 

Vn=~v VL 

The proper value for v is found by trial in Eq. IV. 

THE PROBLEM. 

Proportion a System to lift 66 cu. ft. (500 gals.) per minute 200 feet in the 
lower stage and 650 gals. (87 cu. ft.) per minute, 175' in the upper stage. Assum- 
ing lengths of air pipes to be 500' to lower and 300' to upper tanks. 

Note: — In the following computations it is assumed that no change in tem- 
perature occurs and friction of air and of water in pipes is neglected. 

SOLUTION. 

Horse Power: — From figures given above the average net Horse Power 
= 55. But the max. rate of work per stroke is 10,900 ft. lbs. (see ordinate at 
K.) Assuming the compressor to work at 90 revolutions (or 3 strokes per sec.) 
this will give about 60 H. P. 

Air Pipes: — If the volume of compressor stroke is previously known the 
max. velocity in air pipe of known area can be found by observing that imme- 
diately after switching the whole volume of compressor stroke goes through the 
air pipes. 

Otherwise an approximate rate is : The max. air volume = 6 times the 
average water volume discharge. In this case the rule gives 5.5 cu. ft. per sec. of 
air at 102 lbs. Hence select air pipes 4" diam. 

Ton^j;— They should not be less than 10 times the vol. of air pipe. Hence 
assume V = 450 cu. ft. Then if no receiver were attached V would be com- 



USE. 



617 



puted by Eq. I. which would give V" = 525 ; but by conditions of the problem, 
V" must be = 1.3 V = 585. This requirement can be satisfied by attaching a 
receiver whose volume will be computed by Eq. II. Whence R = 497. In prac- 
tice make Y" and R larger to permit adjusting, which can be done by pumping 
water in or out of R. 

Notes on the Operation: — When air is switched out of V" it expands into 
pipe a and'thereby drops from 91 lbs. to 88 lbs (G" to A) then compressor forces 
air into V but no water will be delivered until pressure in V reaches 102. In the 
mean time pressure in V" will be worked down to 79.5 which will require 47 
strokes (see A to B' and A to B"). 

When air is switched out at V we will have V + R + «' at 102 lbs. while 



Contpressor pB 
375' 



300- 



200- 



JB 

Siritch 



87 cu. ft. per sec. 




100- 




2/ cu. ft. per sec. 



66 cu. ft. per sec. 



FIG. 231. 



only 91 lbs. is necessary to force water out of^V". Hence water will discharge 
without further action of compressor until all pressures drop to 91 lbs. 

The volume of water thus displaced will be 96 cu. ft. This cannot be 
properly shown on the diagram. It occurs between D"' and E'" but as these 
points are coincident in time the effect will be to run the delivery curve up as 
shown in the dotted line near E'". 

Formulas III and IV do not apply after Pn falls below atmospheric pres- 
sure, for V (or V) is then a variable. Hence the broken lines between C and 
D and F and G are not computed. 

The two lines in each pair of heavy verticals S" S" and S' S' are co- 
incident in time. The intervening space is for convenience in showing connec- 
tions between curves. 




I 



USE. 

TABLE 53. — HARRIS' COMPOUND PRESSURE PUMP. 



619 



A. E. Chodzko. 



4 


te Pres- 
q. In. 
insion. 






-h 


ve 

Work 
ession 
very, 
bs. 


ve 

Work 
sion. 
be. 


£ t*-*? 


II 




^« 


«^ 


15 


If Pi 


11 1| 






^ D ■<-> 












«i e3 


Q 


^-•s 








<° 







1 


88.9 


1.18 


0.847 


.89 


25,704 


19,580 


6.124 


2 


73.5 


1.39 


0.719 


.79 


24,768 


15,991 


8,777 


3 


64.1 


1.63 


0.614 


.71 


23,509 


12,937 


10,572 


4 


54.4 


1.92 


0.521 


.628 


22,824 


10,339 


12,485 


5 


46.2 


2.27 


0.44 


.557 


21,270 


8,142 


13,128 


6 


39.2 


2.66 


0.376 


.497 


19,960 


6,267 


13,693 


7 


33.3 


3.14 


0.318 


.441 


18,360 


4,687 


13,673 


8 


28.3 


3.7 


0.27 


.39 


16,517 


3,347 


13,170 


9 


24 


4.36 


0.23 


.349 


15,480 


2,195 


13,083 


10 


20.4 


5.13 


0.195 


.31 


13,738 


1,231 


12,507 


11 


17.3 


6.05 


0.166 


.28 


12,845 


401 


12,444 


12 


14.68 


7.13 


0.14 


.246 


11,088 


-296 


11,384 
141,040 



Work of simple compression of 80 cu. ft. of free air to 90 lbs. gauge 
Work of compound compression 80 cu. ft. of free air to 90 lbs. gauge 

446,306 



Efficiency of the system referred to compound is therefore, 



and referred to simple is 



141,040 
528,000 



at 6600, 
528,000 

at 6600, 
446,306 

= 309 



= 375 



solute. 



141,040 
Po initial absolute pressure in tank. 

final " " in compressor = 90 lbs. g. = 1047 lbs. ab- 

Pn absolute pressure after the nth double stroke. 
Pa " atmospheric pressure. 

\ V-\-a-\-vJ 

V volume of tank = 8 cu. ft. 

a " pipe = 3.24 cu. ft. 

V " compressor cylinder = 2 cu. ft. 

Pn = 104.7X0.849 ^\log. Pn = 2.019947 + n X l" 928965. 

Effective isothermal work of expansion. 

We = 267.87 Pn — 4233.6. 

Effective adiabatic work of compression. 



620 USE. 

Theoretical actual work done in lifting water = 8 X 62.5 X 2.10 = 105,000 
foot-lbs. allowing 85% mechanical efficiency. Real work done = 89,250 foot-lbs. 

89,250 

= 63.2% 

141,000 
Suppose we have six equal-sized tanks. A, B, C, D, E, F (233), arranged 
above each other at distances that we shall shortly determine. Suppose tank A, 
submerged in a sump and an air pipe conducting compressed air at 90 pounds to 
this tank. From each tank to the one above there is an air pipe leading from 
the bottom of the lower tank to the top of the upper one, as shown. From each 
tank to the one above, there is a water discharge tank leading from the bottom 
of the lower one to the bottom of the upper one, as shown, and having a check 
valve on its lower end to keep it full of water. From tank F the discharge is to 
the surface G. On each tank is a check valve, C, opening the tanks to atmosphere 
whenever the pressure falls to atmosphere within the tanks, and closing them 
whenever the water rises against them. Now if tank A be full of water, and air 
at 90 pounds be admitted the water will be displaced into the tank B, a distance of 
210 feet, just as it did with the Merrill pump, but when the water is all discharged 
from A, and just before the water discharge pipe is uncovered, the air pipe lead- 
ing to tank B is uncovered and the air passes up into tank B, expanding against 
the water and pushing it up into tank C, a distance equal to one-half the absolute 
pressure of 90 pounds. This must be so, because tanks A and B being equal 
the pressure becomes 37.5 pounds in both of them when they contain air and not 
water, so now we have the water in C at 87 feet above B, and in a similar manner 
it will be pushed into D and E and F, and finally out at G, distances 46 feet, 25 
feet, 14 and 6 feet, respectively, corresponding to 1/3 and 1/4, i/s and 1/6, the ab- 
solute pressures of 90 pounds. When F is empty the whole system is full of ex- 
panded air at 2.5 pounds, at which pressure it exhausts into the atmosphere. No 
mechanism is necessary except the one small valve mechanism similar to the Mer- 
rill device, and this admits air into A at proper intervals. The rest of the tanks 
take care of themselves. If fine economy is not required, only the water pipe need 
connect the tanks ; the air pipe may be eliminated and also the check valves in the 
water pipes, and the air will drive the water from tank to tank and finally escape. 
The check valves C will then drop open and air may be again admitted at A. The 
water pipes, being always full, do not form clearance. It matters not how much 
water is left in the bottom of the tanks so long as they are all alike. That does 
not form clearance, and, so long as the tank is full before the valve switches, there 
is practically no clearance. The air as admitted to the tanks is made to bubble 
up through the water in small bubbles, through a false bottom, and thus the ex- 
pansion is made isothermal. 

The system can be made double, or in any number of units, so that the dis- 
charge may be constant. The objection to the system for shaft work is in the 
space required for the tanks, which might not be objectionable in some places. 
For outside pumping it would be efficient and easy to install. As to economy, not 
much of a calculation is necessary to show that if the Merrill pump did 175 foot 
gallons of work with one cubic foot of free air, at 90 pounds, and lifted the water 
210 feet, this system with the same air will do 175x388-210, or 320 foot gallons, 



USE. 



621 



because it has lifted the water 87 + 46 + 25 + 14 + 6 feet, or 178 feet further, or 
a total of 348 against 210. This makes the efficiency 22 x 388-210, or 40 per cent., 
quite an advance over the efficiencies of direct acting pumps. 

Another peculiarity is that although 90 pounds pressure corresponds to 210 



T 



S^ 



f'7\ 





Kl 1^1 M 



FIG. 233. 
MULTI-CHAMBER LIFT WITH EXPANSIO 



03"" 
5 f-- 



J- 



N- LI 



622 



USE. 



feet head, it is lifting water 388 feet, so that the cylinder ratios, as it were, are 

inverse. 

If we now study diagram 234, made up from the action of this pump, and 
allowing that the expansion is isothermal, we have A, B, D, C as the original vol- 
ume at 90 pounds in the first tank. This expands to E, F, D, I in the second tank, 
and so on to atmosphere after leaving the sixth tank. It is evident that the tri- 
angular areas A, T, E, etc., six in all, are the expansion losses, but when it is con- 
sidered that these expansions furnish the dynamic head that overcomes the ele- 
ment of time and pipe friction, we see that even if there is loss, it is necessary, 
and if the air had expanded along the isothermal line we would have been obliged 
to have added to our initial pressure and quantity to have overcome these re- 
sistances, consequently, as a pump, it has a high efficiency, for it utilizes about all 



Area Adiabatic : 18.66 
*' Isothermal : 13.41 y 
" Pump Card: 11. 10 / 


A I 


S 


11 

m 


T 


F 


V 




TT 




y^^. 


V 






Jf 


1 


^ ^J 




IV 








r 


FJ_^^ 


X 


■H 1 








w 




.sSSZL.Y 


A^t 


1 


iere 


r 




N 



s J I c n 

FIG. 234. — DIAGRAM OF MULTI-DISPLACEMENT PUMP USING EXPANSION. 



the expansion energy of the air. To calculate it from the card without plani- 
meter, we have as follows : 

The card being 7 inches long, 7 atmospheres high and i atmosphere to the 
inch, we have: 

M. E. P. isothermal — 28.89 pounds.^ 
. We know that Area of Card x Spring- Length = M. E. P. ; therefore, M. E. 
P. X Length-Spring = Area, or, in this case, 28.89x7-15 = 13.41 square inches. 

The card being lined to square inches, it is easy to add up the effective area, 
and we find it to be 7 + 7/2 -f t/z + 7/4 + 7/5 + 7/6-7XI-.05, the latter being 
the area R, Q, Y, or 18.15 — 7.05=11.10 net area. The curve area being 13.41, the 
efficiency of the pump = 11.10-13.41, or 82 per cent., and for the efficiency of the 
system with simple compression, we have as before, the adiabatic area 18.66, and 
the work area 11. 10 divided by this, gives 59 per cent, efficiency for the system. 
Allowing for it the same ratio of losses, viz., 7 to 9, as we did the Merrill, we 
have 59x7/9 = 413-9=^45 per cent., net, nearly the same figures we had before. 
With a compound compressor I should look for 50 per cent, efficiency in this sys- 
tem, and I hope the suggestion will prove interesting enough to encourage some 
one to try it. 



USE. 623 

We come now to what I deem the most interesting and useful class of com- 
pressed air pumps, viz., the motor displacement pumps, using more or less expan- 
sion, otherwise called compound, or multi-cylinder pumps. 

COMPOUND OR MULTI-CYLINDER PUMPS, 

Judging by results, these are very little understood, even by the people who 
build them, so far as their use of compressed air is concerned. The general idea 
has been that if the expansion of air produces such low temperatures that it fre- 
quently freezes a simple pump to a stop, it would be an unwise proposition to 
try further expansion in a compound pump, and consequently the compressed air 
users have practically avoided multi-cylinder pumps. 

I shall hope to show that even a triple or quadruple cylinder pump may be 
not only operated safely but economically with no further addition of heat than 
that supplied by the water itself. 

Before that, however, I shall speak of the phenomenon of freezing. This is a 
very simple matter, easily explained and easily prevented. The compressed air 
being used at full pressure in the pump cylinder, is then exhausted, and, doing 
its expansion work within and about the exhaust ports, reduces their temperature 
until ice is formed in the exhaust, which finally closes the opening. I believe the 
action to be cumulative, and on the same principle used in making liquid air, for I 
have noticed that when once the pump cylinder becomes quite cold the choking 
proceeds more rapidly, the idea being that the colder the air previous to exhaust 
the colder will be the exhaust, which in turn makes the cylinder colder and thus 
the cumulative action goes on rapidly. I have heard that makers have advised 
short ports and conically tapered ones, with no threads, to avoid freezing. I have 
seen pumps with steam injected and pumps with fires under them, and pumps 
submerged in a tank of water, all to avoid the freezing. Where it is not desirable 
to reheat pumps with steam or hot air, there are, to my mind, two simple methods 
of avoiding freezing. First, tap the discharge main with a quarter inch pipe, 
draw down the end of this pipe until the hole is the size of a knitting needle, in- 
troduce this small pipe well into the exhaust of the pump, and let a small amount 
of water continually discharge therein. It will keep the temperature of the metal 
above the freezing point, and thus prevent freezing. The loss of water is very 
small. A pump doing 10 H. P. actual work, and using 250 cubic feet of free air, 
weighing about 20 pounds, would use, I should judge, about 10 to 12 lbs. of water 
per minute, or i^ gallons would be ample for the work. Oi, if it is not desirable 
to waste this water, exhausting through a coil of thin pipe placed in a chamber, 
through which the suction or discharge water circulates, will furnish heat enough 
to the expanding air to prevent freezing. 

The second method for preventing freezing would be to use compound 
pumps, properly arranged. This you will note is exactly contrary to the generally 
accepted practice. Inasmuch, however, as a compound pump is so different from 
two simple pumps having the same sizes of cylinders and using the same pres- 
sures, and inasmuch as the temperature drop on the initial cylinder is about one- 
half that of an equivalent simple pump, it is evident that it will not freeze, and if 
the exhaust be carried through a copper coil over which the water which is being 
pumped flows freely, the air will becon^e about the san^e temperature as the ^yater, 



624 



USE. 



and it will, thus reheated, pass to the compound cylinder at the same temperature 
as it entered the initial cylinder, and, passing from this cylinder, it will exhaust 
without freezing, and the pumping economy will be advanced 30 per cent, or more. 
Each cylinder would thus dispose of about half the reduction of temperature. If, 
however, no water heater was introduced between the cylinders, the initial 
cylinder would discharge the air at a large temperature drop into the second 
cylinder. This gives a cumulative effect to the cooling at the exhaust of the sec- 
ond cylinder, and rapid freezing up would result. This has led every one to be- 
lieve compound pumps impracticable for cold air, but by the introduction of the 
water heated coil between the cylinders, without cost for the heat, the compound 
pump will not freeze and will be more economical. It is evident that the lower 
the range of pressures the less the range of temperatures and consequently the less 
liability to freezing. 

To return now to the compound, direct acting pump : Compound pumps of 
the better class can be given a mechanical efficiency of 70 per cent., which covers 







1 


/ 


^no> 








1 




/ 


/ 


1 




f 




F 


I> 




t 


^// 








s 


< -1-.85 


' *■ 


__---^^^ Afi:t 


o;:ph'i'i- 


w 


Cr 








' 






Jfl 




1 






i 




—a — 


///'/ A 


^ '/'/ 



FIG. 235. — DIAGRAM OF COMPOUND PUMP, WATER REHEATED. 



the losses in the air and water cylinders and the friction in the pipes, with an 
allowance for dynamic head. Their economy depends upon the character and 
amount of the reheating applied to the air. 
There are four general classes : 

1. Reheating with the water pumped. 

2. Extraneous heating before the initial cylinder. 

3. Extraneous heating before the compound cylinder. 

4. Extraneous heating before both cylinders. 

In the first class for mine pumping the temperature of the water may be gen- 
erally assumed to be 60 degrees, and the heater is a shell filled with copper tubes 
and preferably made a part of the suction pipes, the water flowing around the 
tubes through which the air is exhausted from the first cylinder to the second. A 
steam heater, of the Wainwright type, gives the idea, and about one square foot 
should be allowed to every five cubic feet of free air. As stated before, its action 
is to restore the compressed air exhausted from the initial cylinder to normal 
temperature, thus delivering it to the second cylinder at the same temperature as 



USE. 



625 



the first, just reversing the action of th^ inter-cooler during compression, and 
inasmuch as the cylinders use the air at practically full pressure, the expansion 
takes place in the reheater, and the diagram, 235, shows what takes place as far 
as economy is concerned. B, C, E, D is taken at 70 per cent, of the volume fur- 
nished to the pump to cover the mechanical efficiency. This expands to 2.65 times 
its volume (when the initial pressure is 90 lbs.), in the reheater, and F, E, H, G 
is the volume given the second cylinder. The areas = .7 x -(7-2.65) = .7 x 4.35 
= 3.045 + (1.855 X 1.65) = 3.06 = 6.1 square inches. It will be noted that the 
work in both cylinders is alike — 6.1-18.66=32.7 per cent., against 19 per cent, that 
we figured by the same method for the simple pump. A very large gain and 
costing nothing to maintain, the first cost of the heater being small. I cannot con- 
ceive of a more forcible argument in favor of compound pumps. 

For compound compression this efficiency will be increased to 37.5 per cent. 
If our simple pump did 135 foot gallons of work, then this style of compound will 



/ 










3 


. .. . 1 Y 


;■ ■ 



FIG. 236. — COMPOUND DIRECT-ACTING PUMP. REHEATED TO 300° BEFORE THE INITIAL 

CYLINDER. 



give 135 x 32.7-19 = 232 foot gallons for a cubic foot of free air compressed to 
90 lbs. gauge. 

In compound pumps where we have extraneous heating previous to the ad- 
mission of the air into the initial cylinder, let us suppose the heating to be to 300 
degrees Fah., this will be sufficient to increase the volume from 7/10 in our for- 
mer example to i, in other words, to offset all the mechanical losses in the pump, 
and the initial cylinder will be full of air at 90 lbs., and at 743 degrees absolute 
or 283 degrees Fah. When the air is exhausted from this cylinder into the low 
pressure cylinder there is an expansion ratio of 2.65 between the cylinders, pro- 
vided there is a small receiver between the two cylinders, the temperature will 
drop a ratio of 1.32, or, considering the losses by radiation, will reach 60 degrees 
again and will enter the low pressure cylinder in precisely the same condition that 
it did in the former case, and with the same volume, consequently we have no gain 
in this way of reheating, except for the initial cylinder, unless the heating be car- 
ried so that the cylinder will receive it at more than 300 degrees, which might not 
be practicable. In Fig. 236 we have added the area i, B, D, J to our diagram, Fig. 



626 



USE. 



235, and the area of useful work will be i x 4.35 + 3.06=7.41, and, the compres- 
sion area being 18.66, the efficiency is tW6= 40 per cent., against 32.7 per cent, in 
the former case, and for compound compression this will be 46 per cent., and the 
foot gallons of work will be 280 for each cubic foot of free air compressed to 90 
lbs. gauge. 

If, however, there be a reheating between the two cylinders to about 300 
degrees Fah., then the volume entering the low pressure cylinder will be increased 
about 1.43 per cent., and instead of 1.85 as in Fig. 236, it will become 2.65 and oc- 
cupy the area shown as K, E, H, L, as per Fig. 237. 

The useful area in this card will be 4.35 + 4.35 = 8.70, and it will be noted 
that the work is the same in both cylinders, and the final efficiency will be ys\% = 
46 per cent., and if compound compression is used it will become 53 per cent, and 
the foot gallons of work which it will perform will be 326. 

It will be noted that the points K and I are on the isothermal curve, which 
means that we have utilized completely the full pressure work within the isother- 




FiG. 237. 



-COMPOUND DIRECT- ACTING PUMP REHEATED TO 300° BEFORE INITIAL AND 
LOW PRESSURE CYLINDER USING FUEL PRESSURE ONLY. 



mal curve, using two expansions, and if three cylinders be used, and proportioned 
by the same rule, we make a still further gain and our diagram. Fig. 238, will give 
54 per cent, for simple compression and 62 for compound compression, and the 
foot gallons of work it will perform will be 383, and these figures are perfectly 
practical and rather under the mark. 

It is easy to see that more cylinders would add to the economy, but inasmuch 
as three are practical and four are too many, we may as well stop here, and for 
more economy on this system the reheating must be carried higher, and inasmuch 
as 400 degrees is perfectly practical and as easy to obtain as 300 degrees, this 
would add 16 per cent, to our percentage of card area, and would give 63 and 72 
per cent., respectively, and our foot gallons of work would be 444 foot gallons, 
and the dotted lines on the diagram will represent the shape of the card and show 
bow^it may extend over the isothermal curve. This I call the practical limit. 

In the diagrams shown I have always assumed that the second or third cyljn- 



USE. 



627 



ders are so proportioned that there is no increase of pressure by reheating, simply 
increase of volume. 

We have seen that a cubic foot of free air at 90 lbs. pressure will perform, 
under proper conditions, 444 foot gallons of work. This is 3,685 foot lbs., which 
may be decreased 5 per cent, as the cost of reheating, making net 3,500 foot lbs. of 
work. On account of the 70 per cent, efficiency of the compound pump, we gave 
it one cubic foot of free air in our calculation and called it 7/10. The air itself 
must be given credit for this, and if in the 70 per cent, efficiency pump it did 3,500 
feet of work it really was yielding up 15_2_2^ or 5,000 foot lbs. 

It takes 5,600 foot lbs. of work to compress this air in a compound compres- 
sor. The air has, therefore, shown in its work an efficiency of 90 per cent, as a 
motive power at 90 lbs. pressure, in triple, compound, direct-acting pump cylin- 
ders, triple reheated to 300 degrees, a result entirely different from what we are 
generally almost forced to believe. 

Fig. 239 is a copy of a pair of actual cards illustrating the principle of full 
pressure working. It will be noted that the expansion shown is small, and if the 



H. p. Area 3 32 




FIG. 238. — 3-CYLINDER REHEATED COMPOUND PUMP^ USING FULL PRESSURE ONLY. 



reheater had a little larger capacity the diagram would be rectangular. Unfor- 
tunately, at the time these cards were taken, the pump was throttled, and the air 
was wire-drawing from 70 lbs. to 50, so that its efficiency is diminished. The 
pump, however, was delivering 396 gallons per minute 390 feet high and consum- 
ing 600 cubic feet of free cold air at 50 lbs. pressure, and giving 250 foot gallons 
per cubic foot of free air, at 50 lbs. pressure, with an efficiency, referred to 50 lbs. 
of 65 per cent., referred to 70 lbs. of 52 per cent., the total energy from 70 to 50 
being lost in the throttling of the pump. It illustrates, however, our proposition 
and confirms our figures. 

I believe that it is the idea in general that the best result in compound pumps 
using compressed air is to get as much expansion within the cylinders as is pos- 
sible, and the highest efficiency which could be obtained in this manner would be 
when there is no drop whatever between the high and low pressure cylinder, and 
the air is expanded to atmosphere in the low pressure cylinder, as shown by the 



628 



USE. 



ideal card, Fig. 240. This would require heating to 454 degrees Fah., the tem- 
perature of adiabatic compression. 

The practical action of a once reheated compound pump Is as follows : The 
air enters the high pressure cylinder, we will say, at a temperature of 200 degrees, 
and at 100 lbs. pressure. This air operates at full pressure throughout the whole 
stroke, and there is no drop whatever in its temperature. The exhaust valve 
opens; there being a considerable space between the high and the low pressure 
cylinder, in the shape of pipes and clearances, and, if there be an intermediate re- 
heating, in the additional space for the reheater ; the pressure immediately drops, 
we will say, to 50 lbs., and the temperatures suffer in adiabatic proportion to the 
absolute pressures. 

This expansion from 100 to 50 lbs. does no work whatever and is entirely lost. 
The volume of air shrinks in proportion to the absolute temperature, and then 
passes into the low pressure cylinder, and immediately commences to expand 
therein as the piston commences to move. Here will be a case of adiabatic ex- 
pansion, for the temperature in the cylinder must drop as the pressures drop, and 



JULT 30, 1900. Tbmpebatures 

Between Heater and Throttle 248° 

Throttle and H. P. Cylinder. . 200° 

Exhaust H. P 78° 

Inlet L.P 289° 

Exhaust L. P 134° 



July 30, 1900. Temperatures 

Between Heater and Throttle 229° 

Throttle and H. P..... 196° 

Exhaust H. P 76° 

Inlet L P 283° 

Exhaust L.P ^ 133° 



Air Gau^e, 


70 Lbs. 




"Water Gauge, 


160 " 


No. 13. 


Stroke, 


141^ Lbs. 


W. H. P. H. 


Revs. p. m., 


24 


Spring 40 


H. P. Cylinder, 


16 inches. 





Air Gauge, 
Water Gauge, 
Stroke, 
Revs. p. m., 
L. P. Cylinder, 



72 Lbs. 

160 " No. 11. 

HVi Lbs. W. L. P. P. E. 
23 Spring 16. 

25 inches. 



^ 



FIG. 239. 



the expansion takes place adiabatically to the end of the stroke, where, with a ter- 
minal pressure, we will say, of ten lbs., it drops out into the atmosphere at a tem- 
perature probably a few degrees below that of the atmosphere. 

The M. E. P. of the expansion from 50 lbs, down to, say, 10 lbs, is not a very 
large proportion of the total possible expansion work of the air from 100 lbs. 
down to ID lbs., and this is still further reduced by the fact that while we have 
the expansive work in the low pressure cylinder we have also a variable back pres- 
sure on the high pressure cylinder, which means an unequal load on the piston and 
a consequent variable speed. 

An attempt has been made to realize the work of expansion between the two 
cylinders, but owing to the natural mechanical construction of the pump it is 
impossible to realize more than a small part of it, and I believe the correct method 
of operating these pumps is to do all the expanding between the cylinders and re- 
store the volume by reheating, and use only full pressure in the cylinders. We 



USE. 



629 



avoid any temperature drops in the cylinders and we have a constant pressure 
therein and a consequent constant speed and constant back pressure. 

In a compound pump the proportion of the low pressure cylinder to the high 
will then be larger than is in use at present, for the low pressure cylinder will be 
operated at its terminal pressure throughout the stroke ; in other words, the card 
will be rectangular. 

We believe that instead of using two cylinders, with a greater ratio of areas, 
that it would be better to use three cylinders and proportion the areas between 
them, so as to have the terminal pressure desired. In this way the drop between 
i'he cylinders would be small, and the opportunity to take advantage of double 
heating would be considerable, and the ideal situation, theoretically speaking, 
would be where a large number of cylinders would be in operation, one after the 
other, with only a sufficient drop between them to give them the necessary dynamic 




FIG. 240. — IDEAL COMPOUND CARD. AIR HEATED TO 454 FAH. 



head. The combined card would then represent a series of steps considerably 
overlapping any possible card that could be made by an adiabatic expansion. 

If it were possible ordinarily to expand without drop from the initial pres- 
sure, there would be no criticism of ordinary methods, but, inasmuch as a drop 
must be made, the question naturally arises, is it not better to make the complete 
drop and take advantage of the situation when the drop occurs and which is neg- 
lected when a combination is made of half drop and half expansion? The Com- 
stock offers every possible opportunity for this kind of a proposition. The tem- 
perature of the water is 120 degrees, and the pump and the water and the inter- 
coolers and the air and everything will always be at that temperature, except if the 
air expands in any one of the cylinders, and it is well known that air is such a 
poor conductor of heat that no matter if the cylinder walls be hot it will drop its 
temperature in expanding; in other words, the expansion in the cylinders would 
be adiabatic, whereas, if a complete drop is made and the temperature restored 
between the cylinders, and then it is used in the cylinders at full pressure through- 
out the stroke, it will approach nearer an isothermal expansion for the air than 
in any other kind of a practical method with direct acting pumps. 



630 USE. 

The economical expansion of air must ever be the exact reverse of the eco- 
nomical compression of air, and the ideal air compressor would be one of many 
stages with a small rise in pressure between each two stages, just sufficient to keep 
the air moving, and an intercooler to take out the small increment of heat for each 
stage, making practically rectangular cards between the stages; and the natural 
reverse of this, for the economical expansion of air, would be a multitude of cyl- 
inders with sufficient drop between them to maintain a circulation of the air, and 
reheaters between each two cylinders, making a practically rectangular card for 
expansion in each cylinder. 

As illustrating the principle which I advocate, attention is called to the di- 
agrams Fig. 241, which are from a compound pump with the air reheated before 
entering the initial cylinder to 165 degrees Fahrenheit. This pump is doing fair 
work, raising 450 gallons per minute 424 feet high. It receives air at 63 pounds 
gauge and 165 degrees Fahrenheit, takes air at practically full stroke, exhausts 
into the pipe connecting the two cylinders, drops to 35 pounds gauge and gradually 
expands, as back pressure against the high-pressure piston, until 12 pounds is 
reached. The low-pressure piston receives the pressure at 27^ pounds and the 
air is expanded to 11.5 pounds, and it then exhausts against 2 pounds back pres- 
sure into the atmosphere. 

Assuming the volume of the high pressure cylinder to be one cubic foot, and 
having no clearance, etc., inasmuch as we are about to make a comparative state- 
ment, we find that the foot pounds of work on the high-pressure piston is 6.797 
foot pounds, and on the low-pressure piston, 1,581 foot pounds, a total of $8,378.5 
foot pounds. 

Now let us consider another method. If we use the air at 63 pounds on the 
same high-pressure piston and let the exhaust make a complete drop to 11. 5, 
pounds, the work on the high-pressure piston will be 7,416 foot pounds, and if we 
reheat the air in the receiver to 165 degrees and make the low-pressure cylinder 
of such a size that after receiving the air at 11^ pounds it will exhaust at 2 
pounds, thus preserving the relation of the previous problem, the cylinder ratio 
will be 3.06 and the work on the low-pressure cylinder becomes 4,186 foot pounds, 
making a total of 11,602 foot pounds, or a gain of 40 per cent. 

Suppose we make it a triple cylinder pump and make each cylinder do the 
same work and reheat to 165 degrees before the first and between each two, and 
use the same two pounds back pressure, then the initial cylinder will take the 
pressure at 63 pounds and do 4>550.4 foot pounds, the intermediate will take the 
pressure of 31 pounds and do 4,450.4 foot pounds of work, and the low-pressure 
cylinder will take the pressure at 12.4 and do 4,550.4 pounds and exhaust at 2 
pounds back pressure, making a total of 13,651 foot pounds, or a gain of 64 per 
cent. The pump is now doing about 220 foot gallons of work. If we add 64 per 
cent, to this we will have 360 foot gallons. We claimed 383 in our former di- 
agrams, for higher reheating, which checks results quite nicely. The cylinder 
ratio in the above will be for equal work in the cylinders, the cube root of the ratio 
between initial and absolute pressures, 1.7, making the pressure 63, 31 and 12.4, 
respectively. The atmospheric pressure was in this case 13.5 pounds. 

Your attention is particularly called to the difference between steam and air 
practice, for here is a triple expansion, so called, operating with 63 pounds initial 



f9~r\^- 



USE. 



63t 



pressure properly. The number of cylinders that could be properly used would 
have to be determined by practice, the limit being when their mechanical de- 
ficiency offsets their economy. 

There are many places where it would be inadvisable to use fire or steam for 
reheating, on account of heat or annoyance or expense, and it is in such situations 
that what I term a water reheater will supply enough heat units to render the 
pumping economical. A general illustration is given in Fig. 241, which sTiows 



^J6 



'17 



JO- 



J4 



1 

< 


1 










-13 






















1 






w 






I 







FIG. 241. — DEVICE FOR WATER HEATING OF AIR. — PAT. JUNE 7, \l 



how the suction water may, in passing around corrugated copper tubes, render 
valuable service in heating the air. 

In actual practice the difference in the number of revolutions of the compres- 
sor to do the same work speaks immediately for the economy of the apparatus. 
In pumping muddy water through the reheater the deposit of mud on the tubes 
could be readily detected by noticing the increased air consumption. It is very 
evident that the more successive air cylinders on a pump, the less drop in pressure 
will be made from one cylinder to another, and, consequently, less dropping of 
temperature. It is for this reason that in a multi-cylinder pump water at ordinary 
temperatures, acting through a number of cylinders, will yield up as many and 



632 



USE. 



perhaps more heat units for useful work than a high temperature reheating before 
the first cyHnder. It gives more time for correction, and with air, which is a poor 
conductor, time is required. 

Referring to our last example, using three cylinders, it is evident that if the 
water was at 60 degrees Fahrenheit the only difference in results would be the 
increased volume due to the higher temperatures. This we counted as 1/5. De- 
ducting, therefore, 20 per cent, from 13,651 foot pounds, we have 10,921 foot 
pounds, which would be accomplished on the water-heating plan, which is more 
than was accomplished by heating the initial cylinder of a compound pump to 165 
degrees.. Please note that this heating costs nothing, and the extra cost of the 
pump should not be considerable. If by water reheating a triple cylinder pump 
will do 300 foot gallons per minute, the cost for pumping water would be one- 
Air 165° No reheating. 




20 Sprltirj 



FIG. 242. — CARDS FROM COMPOUND PUMP I4" + 24" CYLINDER. HEATED TO 165° BEFORE 

INITIAL CYLINDER. 

half what it would be in an ordinary direct-acting pump, which power saving 
would of itself soon pay the cost difference. 

COMBINATION OF DISPLACEMENT AND AIR LIFT. 

It seems proper under the head of air lift pump to speak of the Wheeler Pneu- 
matic Pump, which is a combination of displacement and air lift, and can be used 
in places where there is no proper submersion for the air lift. In fact, the sys- 
tem might be called an air lift system with artificial submersion, shown generally 
in Fig. 243. 

The pump has two displacement chambers and an automatic valve attached, 
similar to the Merrill pump, and the displacement action takes place similarly, one 
chamber filling while the other empties, the exhaust being into the atmosphere and 
the expansive work of the air being lost. The Merrill pump discharges from the 
chambers directly to the final point of delivery, while the Wheeler pump keeps the 
discharge pipe filled with water at a certain height, and an air jet at its lower 
extremity "air-lifts" this water to the final delivery. H. C. Behr, Esq., tested this 
pump during 1899, and his conclusions in his report are as follows : That the ef- 
ficiency of the machine, as tested, is such as to compare not unfavorably with the 
ordinary steam or air driven direct acting pumps of moderate size and as used un- 
derground in mines ; that the operating expenses could generally be expected to be 
considerably lower than for such pumps on account of the slight cost for repairs 
and the replacement of worn parts; that it should require less skill and experi- 
ence to operate and maintain this pump than a direct acting pump. The efiicien- 
cics found might be somewhat increased in cases where a very efficient compress- 
ing plant is available. The efficiency will not compare favorably with high-class, 
air-driven compound pumps reheated. The objection to the pump is that it is 



pp- 



» 



USE. 



633 



not capable of raising the water by suction, and is thus incapable of charging 
itself. It must be submerged, or the supply must be higher than the water 
chambers. 

The Wheeler device, Fig. 243, permits the displacement to take place with low 
pressures, and thus adds to the efficiency. The table marked Fig. 19 accom- 




-^.y 



FIG. 243. — A IS DISPLACEMENT CHAMBER RAISING WATER TO C, WHEN AIR FROM 
PIPES AT B COMPLETE THE LIFT. 



panics Mr. Behr's report. Test No. 21 shows the best efficiency, viz., 30 per cent, 
air pressure, 33.75 pounds work done; 4 horse power; water lifted, 1,271 pounds; 
quantity of air, 7.78 pounds per minute. Comparing this with the results ob- 
tained in the discussion of air lift and simple displacement pumps we have: Air 



634 USE. 

pressure, 33.75 pounds — 10 per cent, for dynamic head, equals 30 pounds for 
active pressure. The equivalent head is 70 feet, consequently the v^^ater v^^ill stand 
70 feet in the discharge pipe and the air lift will be 35 feet, giving a submersion of 
2 to I, and air lift pressure of 33.75 pounds. 

Referring to the tables of air lift experiments, tables marked Table 55, we find 
that 2 cubic feet of air to i of water will do the work. There was practi- 
cally 20 cubic feet lifted, making 40 cubic feet of air required at 33.75 pounds pres- 
sure, or 4.80 horse power. The displacement of 20 cubic feet of water at 30 pounds 
required 22 cubic feet of air at 33.75 pounds pressure. Allowing 10 per cent. 
clearance, which was 72 cubic feet of free air, this, at 12 horse power per 100, 
equals 8.64 horse power, 8.64+4.80=13.44 horse power, almost identical with re- 
sults shown in the table. There can be no question but that the economy of this 
system could be greatly enhanced by using the expansive force of the air that is 
lost in exhausting from the displacement chambers, and one of the easiest means 
of doing this is on the principle which I suggested for the multi-stage displace- 
ment pump, as illustrated in Fig. 233. 

CUMMINGS, OR TWO-PIPE, SYSTEM. 

This is a simple system, consisting in compressing the air to a high pressure, 
say 200 pounds per square inch, the idea being that full-pressure motions are more 
economical the nearer you approach full pressure. For instance, from o to 100 
pounds we observe quite an extended compression curve, while from 800 to 900 
pounds there would practically be no curve, but simply full pressure work, the 
part one wishes to utilize in direct acting pumps. 

Take the card No. i. Table 55, and it will be noted that the compression area 
is A, B, C, E only, the area. A, F, G, H, being always back pressure. The area 
of the compression is, therefore, 8 square inches; the work done is calculated at 
70 per cent., as with the other examples, and this area will be 3.04; 3.04-8 de- 
grees=38 per cent., and if reheating be used to 300 degrees and the exhaust be 
cooled off before returning to compressor, the efficiency will be 50 per cent., al- 
most double the efficiency of the ordinary direct acting air pump. If now we 
look at diagram No. 2, where we compress from 90 to 180 and exhaust at 90, we 
have an efficiency of 50 degrees cold, which would be increased by 7-5 if reheated 
to 300 degrees, or 70 per cent. These percentages are probably marred by fric- 
tions and leakages which I have no means of ascertaining, but I should judge 
these could be kept within 10 or 15 per cent., making the simple pump show an 
efficiency of probably from 50 to 60 per cent., with compound compression. 

These pumps can also be compounded with considerable gain, but it would 
easily form the subject for another paper. I wish to remark that I cannot under- 
stand why this system has not been pushed for compressed air station pumping. 
I believe it will be very satisfactory and economical, and some day will be ex- 
tensively used. It has one advantage over the Harris system inasmuch as the 
back pressure is constant, and ordinary pumps may be operated with it. The 
principal objection is the high pressure and consequent leakage and the double 
set of pipes and joints. This system should be regarded with high favor. 



USE. 



635 



TABLE 54. — RESULTS OF TEST OF WHEELER PNEUMATIC PUMP. 

By H. C Behb. 



F 


II. 


III. 


IV. 


V. 


VI. 


VII. 


VIII. 


IX. 


X. 


1 


0) 

If 

1^ a 

>< 


1^ 
Pa 

li 


If 
1 1 


ft'S 
aa 


Water.H.P, 


Efficiency Based on 
Comparison of Work Re- 
turned, with Least Work 
Theoretically Needed 
for Compression. 


11 

afM 

a 

st 


Total Efficiency Product 
of Columns VII and VIII, 
Multiplied by j%% for 
Efficiency of Compress- 
ing Mechanism. 


Operating. 


1 

p 

1 


i4 


Mo 

Us 

AM 




Lbs. per sq. in. 


Lbs. 


Lbs. 


Per Min. 


H.P. 


Per Cent. 


Per Cent. 


Per Cent. 


H.P 


5 


41.000 


12.270 


1,971 


18.00 


6.271 


42.48 


69.4 


25.02 


25.0 


14 


39-000 


12.050 


1,948 


18.50 


6.198 


41.75 


70.6 


25.05 


24.7 


13 


39.000 


9.137 


1,481 


15.50 


4.712 


44.00 


70.6 


26.40 


17.8 


1 


34.500 


13.106 


1,888 


17.00 


6.007 


41.91 


73-3 


26.08 


230 


% 


34,500 


9,079 


1,423 


15.00 


4.528 


45.52 


73-3 


28.36 


15.9 


21 


33750 


7.780 


1,271 


12.75 


4.033 


48.09 


73.8 


30.17 


13.3 


15 

1 


33500 


11.020 


1,716 


16.25 


5.460 


46.04 


73.9 


29.90 


18.2 


33000 


13.687 


1,935 


18.00 


6.158 


42.08 


74.2 


26.53 


23.2 


6 


30.375 


5.770 


785 


8.20 


2.497 


42.80 


75.8 


27.40 


9.1 


3 


29.500 


13.060 


1,668 





5309 


40.56 


76.3 


26.30 


20. 


22 


29.250 


9.810 


1,426 


14.50 


4.386 


44.86 


76.5 


29.24 


15.0 


20 


29.125 


7.650 


1,162 


11.00 


3506 


46.12 


76.7 


29.90 


11.7 


4 


27.250 


13.800 


1,633 


15.50 


5.196 


39.33 


78.0 


.26.07 


19.9 


17 


24.125 


10.080 


1,160 


13.00? 


3.690 


39.84 


79.5 


29.90 


13.7 


9 


24.125 


5.340 


730 


7.75 


2.323 


50.15 


79.5 


33.90 


6.8 


10 


23.'J50 


10.120 


1,133 


11.00 


3.605 


40.43 


79.8 


27.40 


13.1 


18 


19.625 


7.390 


608 


6.00 


1.935 


33.54 


82.2 


23.40 


8.2 


11 


19.500 


9.397 


834 


8.25 


2.654 


36.35 


82.3 


25.40 


lO.O 


19 


19.375 


7.600 


626 


8.50 


1.992 


33.89 


82.4 


23.70 


8.4 


7 


19.000 


9.780 


856 


7.80 


2.724 


36.35 


82.6 


25.50 


lO.O 


8 


14.500 


7.140 


350 


4.00 


1. 114 


24.14 


85.0 


17.44 


6.3 



'olumn Pipe 4 Inch Diameter, 
.ift, 105 Feet. 



Note — Test No. 16 was 
uncertainty of 



thrown out on account of 
speed counter observation. 



I 



636 



USE. 



TABI.E 55. — TABI.K OF KXPERIMEN 



2. 



4. 



8. 



9. 



10. 






o-S 






ftps 



0) d 

3 






oil 






fa 



ft-- 



O ei 
fa 

!^ O 

&5 



Of; 



O Pi^ 

+3 as 
(§0h 



59 
45 
30 
59 
46 
30 
22 
60 
35 
22 
60 
60 
38 
19 
34 
60 
41 
22 
60 
27 
22 
60 
30 
19 
60 

34 
18 
60 
60 
60 
28 
60 
60 



31-15 

27.86 

25.64 

30.69 

26.4 

24.78 

24.16 

24.1 

17.58 

16.17 

20.58 

18.75 

1529 

12.28 

12.35 
20.46 
15.80 
12.52 
22.13 

15-22 
14.52 
23.12 
17.46 
16.2 
17-05 
10.17 
7.46 
15-87 
31.66 
31.66 
25.28 
31.66 
31.28 



4.1 
3.8 
3. 
5.2 

5-1 
4.6 

4.25 
3.85 
3.15 
2.6 

3-2 
2.1 

2.75 

1.6s 

3.4 

4.5 

4.3 

3-74 

5. 

4.5 

4.4 

5-4 

5.2 

4.72 

2.8 

2.3 

1-25 

1-5 
4.1 
2.9 
4.1 
4.1 
41 



75.55 

75.55 

75.55 

35-53 

35.53 

35-53 

35.53 

54-7 

54.7 

54.45 

63.16 

70.66 

63.16 

63.16 

31.5 

2525 

25-25 

25.25 

20.25 

20.25 

20.25 

15.25 

15.25 

15.25 

36. 

36. 

36. 

41. 

75.78 

75-78 

75-78 

75-8 

75-8 



55.78 

55.78 

55.78 

55.5 

55.5 

55-5 

55-5 

36.33 

36.33 

36.58 

27.87 

20.37 

27.87 

27.67 

20. 

26.25 

26.25 

26.25 

31.25 

31.25 

31.25 

36.25 

36.25 

36.25 

15.5 

15.5 

15.5 

10.5 

55. 

55. 

55. 

55. 

55. 



77 

78** 

79° 

74° 

78° 

78° 

78° 

78° 

78° 

74° 

80° 

76° 

80° 

79° 

79° 

69° 

70° 

70° 

72° 

72° 

72° 

74° 

73° 

73" 

74° 

74° 

73" 

76° 

82" 

84° 

84° 

8i*» 

80° 



72.6' 

70.7" 

74° 

72" 

71.6' 

73-2° 

72.5' 

73" 

73° 

74° 

77" 

72° 

74.5° 

75° 

71.5' 

66° 

66** 

66.5' 

67.5 ' 

68° 

67" 

67° 

69° 

69° 

69.5° 

70"^ 

70° 

72^" 

70° 

71° 

71° 

70° 

70'' 



68° 

68° 

68° 

71.6° 

68° 

68° 

68° 

70° 

70° 

69° 

69° 

69° 

70'' 

71° 

69° 

67° 

67" 

67° 

69° 

69° 

69° 

68.5° 

69° 

69° 

69-5° 

70° 

70° 

70° 
108° 
110° 
114° 
116° 

82° 



.0799 
.1488 
.0824 
.3259 
.3105 
.2398 
.1968 
.1538 
.0931 
.0576 
.0968 
•0338 
.0663 
.0185 
.1126 
.2270 
.2026 
.1439 
.2954 
.2270 
.2146 
.3593 
.3259 
•25^1 
-0693 
.0424 
.0093 
.0146 

.1799 
.1691 

.0757 
.1799 
.1796 



USE. 



637 



H AIR lylFT PUMP. 



12. 


13. 


14. 


15. 


16. 


17. 


18. 


19. 


20. 


21. 


22. 


23. 


£ 


•sl 


.d ■^ 


«fl' 




M<j; 


MaJ 


Bi 


^ eb °^ 


;S:§i 


"g-iioJ 


d 


Id 


4. 


-K 


1^ . 






a 


^^. 


0^3 






a 

s 


•* . 


S^ w 


«j 


Sw w 


aw 


0, w 


0, w 


U M 


«M CI • 


S^M 


OCC5Q4J 


a 




0) 


^ 

tw 




0BO 








«53 




OS 


r 

a 


4^ 





0^0 

u 
bfl 

p:5 


w 




a> 


a 


«3^ 


fl 

So 

tf5 


. alii 
5S^a 




16,576 


850 


1.086 


2616 


832 


652 


80 


88 


8 


63 


2583 


33 


'76,4 


703 


.878 


1864 


481 


325 


39 


38 


5 


37 


1628 


38 


: 53,495 


389 


•552 


1 180 


159 


155 


19 


14 


I 


13 


1050 


33 


'3i,578 


724 


1.086 


2569 


1050 


458 


,80 


88 


15 


58 


2473 


28 


31,204 


690 


.846 


1842 


570 


400 


48 


48 


10 


68 


1834 


37 


•55-39 


533 


.552 


1155 


325 


155 


19 


14 


4 


33 


1083 


46 


P9,662 


437 


.405 


834 


160 


97 


II 


II 


2 


18 


736 


52.4 


'50,329 


526 


1. 104 


2269 


631 


s8o 


89 


86 


9 


12 


1933 


23 


^37,325 


318 


.644 


1072 


118 


190 


29 


28 


2 


14 


699 


30 


52,726 


196 


.405 


636 


36 


77 


II 


II 


5 


4 


340 


31 


'21,902 


382 


1. 104 


2046 


137 


281 


89 


86 


2 


44 


1021 


19 


42,962 


149 


1. 104 


1851 


401 


514 


89 


86 


6 


IS 


1260 


8 


11,988 


250 


.669 


105 1 


106 


194 


35 


34 


2 


12 


633 


24 


72,965 


70 


.350 


450 


8 


54 


8 


8 





I 


147 


16 


47,696 


222 


.616 


795 


80 


137 


28 


28 


2 


15 


508 


28 


31,285 


358 


1. 104 


2039 


618 


495 


89 


86 


15 


115 


1775 


18 


98,247 


320 


.754 


1 175 


280 


230 


41 


39 


7 


52 


969 


27 


93,286 


226 


•405 


528 


66 


65 


II 


II 


I 


12 


392 


43 


47,296 


374 


1. 104 


2147 


832 


537 


89 


86 


20 


152 


2090 


17 


39,061 


287 


.497 


748 


167 


no 


18 


17 


4 


32 


635 


37 


32,826 


272 


.405 


589 


118 


71 


II 


II 


3 


22 


507 


46 


11,183 


342 


1. 104 


2209 


926 


582 


89 


86 


25 


141 


2091 


16 


64,01 


311 


.552 


911 


352 


III 


19 


14 


10 


66 


883 


34 


44.906 


241 


.350 


550 


133 


59 


8 


8 


3 


25 


477 


44 


27,475 


156 


1. 104 


1800 


182 


398 


89 


86 


5 


34 


950 


9 


6,026 


93 


.616 


880 


Z7 


123 


28 


26 


I 


7 


315 


II 


9,461 


21 


.331 


288 


2 


36 


7 


7 





14 


73 


7 


16,575 


38 


1. 104 


1712 


38 


360 


89 


86 


I 


7 


619 


2 


09,577 


852 


1. 104 


2685 


836 


674 


89 


86 


9 


65 


261 1 


32 


44,054 


801 


1. 104 


2685 


792 


674 


89 


86 


9 


70 


2521 


30 


49.554 


359 


•515 


1091 


92 


161 


19 


18 


I 


7 


719 


33 


16,575 


852 


1. 104 


2685 


836 


674 


89 


86 


9 


65 


261 1 


32 


16,575 


851 


1. 104 


2666 


836 


674 


89 


86 


9 


65 


2610 


32 



638 



USE. 



AIR LIFT PUMPING. 

While the air lift system of pumping has been brought recently to the atten- 
tion of the public, it is not a new thing, there being records of its use more than 
100 years ago. 

The honor of putting the air lift system in practical shape is due to Dr. Julius 
Pohle, who came to San Francisco from Arizona, where he had been experiment- 
ing with several plants, one with a lift of 300 feet. Dr. Pohle established him- 
self at the office of Rix & Firth, who interested themselves to the extent of ex- 
pending considerable money in experiments to determine the efficiency of the 
system. A ten-inch well was sunk sixty feet deep on a piece of property belong- 
ing to the Mechanics' Institute, San Francisco. The bottom was cemented, a 
gallows frame 75 feet high was erected over it, and a tank and weir constructed 
over the well to measure the water flow. Air and discharge pipes were arranged 




FIG 244. — DIAGRAM ILLUSTRATING THE CUM MINGS SYSTEM. 



so that many different ratios of lift and submersion could be tried. The com- 
pressor had a compound air cylinder, actuated by a Corliss engine of 50 horse 
power. The well-known civil engineer, Mr. B. M. Randall, conducted the experi- 
ments, and they were made on August 27, 1899. The results showed efficiencies 
as high as 52 per cent. The records of this test were tabulated, and I have repro- 
duced them for this occasion, not only for the information the table contains, but 
as an interesting point in the history of air lift pumping, for it is the first record 
of results. 

Messrs. Brown and Behr tested the experimental plant referred to, and in a 
paper read before this society in 1890, stated that the greatest efficiencies were 
obtained when the submersion of the pipe was twice the lift, and at this an effi- 
ciency of 50 per cent, was obtained. 

Quite extensive experiments have been made in Germany, to determine the 
efficiency of the air lift, and their results fall somewhat short of the percentages 
obtained in this country. The efficiency was the ratio of work in discharged water 



USE. 



639 




TABLE 56. — EXPERIMENT IN ARTESIAN AIR LIFT PUMPING. 









1" 




.s 




.£j 




i 














^fe 




<«1 




<J 




m * 






<u 




.2 
1 





1^ 
^.1 


1 


1 



i 


1 


1 


s 

OS 




?? 


<a 





^ 
g 


1 


r 






1 

>-• 






^ 




<1 
.2 


Q 


09 


^ 


n 


m 


& 


<1 


w 


04 


G? 


w 


w 


K 


950 


5&8 


200 


6' 


180 


1H5 


73 


24 


33 


1,300 


11 


46 


.8-1 


050 


5&8 


200 


6' 


110 


135 


41 


165 


30 


800 


6 


36 


1.3-1 


950 


5&8 


200 


6' 


146 


135 


56 


20 


32 


900 


7 


35 


1.2-1 


700 


7 


20 


1 


100 


120 


38 


16 


30 


800 


6 


38 


1.2-1 



640 



USE. 

TABI^B 57. — TABLE FOR AIR I.IFT PUMPING. 






2:^ 












60 TO 100 LBS. PRESSURE. 



10 


12 


92 


108 


80-120 


200-175 


232-205 


12-17 


15-30 


3-2 


12 


15 


165 


195 


80-120 


350-310 


420-370 


22-32 


26-36 


3-2 


14 


16 


245 


288 


80-120 


525-465 


620-550 


35-45 


38-55 


3-2 



30 TO 60 LBS. PRESSURE. 



12 


12 


132 


152 


40-80 


330-285 


380-325 


12-18 


14-20 


3-2 


14 


15 


229 


270 


40-80 


570-500 


675-580 


22-30 


25-35 


3-2 


16 


16 


312 


368 


40-80 


780-670 


920-800 


30-40 


35-50 


3-2 



10 TO 30 LBS. PRESSURE. 



14 


12 


183 


216 


10-40 


640- 450 850- 540 


8-18 


10-22 


3-2 


16 


15 


293 


345 


10-40 


1000- 730 1200- 860 


13-30 


15-35 


3-2 


18 


16 


408 


480 


10-40 


1400-1000 1700-1200 


18-40 


21-50 


3-2 



to the indicated compressor work, and ranges from 45 to 30 per cent., with 
smooth pipes — a lift of 50 feet, and a submersion of from 4 to 3 to 3 to 2. 

The amount of water discharged increases with the quantity as well as the 
pressure of air, but the efficiency falls away very rapidly /^^hen the output is 
forced. A submersion of 50 feet and a height of discharge of 25 feet, with in^ 
creasing quantities of air, gave quantities of water from 4 cubic feet to 15 cubic 
feet per minute ; the quantity of air varied from 7.6 to 105 cubic feet per minute, 



r 
I 



USE. 641 



and the ratio of free air to the water lifted varied from 1.96 to 7.60 cubic feet of 
air to I cubic foot of water, the efficiency being in a like proportion. 

In another set of experiments, with lifts from 43 to 230 feet, submersion from 
92 to 400 feet, from 2.9 to 5 cubic feet of air was required per cubic foot of water 
pumped, and the pressures from 30 to 160 pounds. The quantity that can be 
handled is practically unlimited. 

It is safe to calculate on velocities in the pipe from 4 to 8 feet per second, 
and it will take from 2 to 3 cubic feet of atmospheric air per cubic foot of water 
pumped for heights from 15 to 50 feet and from 50 feet to 160, I should figure, on 
from 3 to 4 cubic feet of air per cubic foot of water. I believe for very low heads 
the air consumption may be still further decreased and 1.5 cubic feet of air will 
lift a cubic foot of water 20 feet high. 

Engineering News, Vol. 37, Page 140, gives some interesting data on air lift 
pumping at Rockford, 111. The pumping was done from 4 wells, 84 feet, 82.5 and 
59 feet from surface to water while being pumped and 7^ additional into a tank, 
with an air pressure of 76 pounds per square inch. The wells were close to- 
gether. A 2j^-inch pipe led from the reservoir to each well, and a iJ/^-inch pipe 
was continued in the well casing, with 225 feet submersion. The discharge was 
2,000,000 gallons per 24 hours. From the steam indicator diagrams, 124 horse 
power was used. The average yield was 1,401 gallons per minute, and the net 
work done was 24 horse power, or an efficiency of 20 per cent. A 14 x 22 duplex 
compressor made 96 revolutions to do the work. This would give about 600 
cubic feet of free air. About 200 cubic feet of water was pumped, or 3 cubic feet 
to I, a result which is average. The efficiency is low, because the compressor 
took too much power. In a compound compressor 600 cubic feet of air should 
be compressed to 76 pounds for an expenditure of not to exceed 100 horse power. 
This would make the efficiency about 25 per cent. The air pressure was excessive 
and was due, no doubt, to the small well casing, because with proper well pipes, 
50 pounds air pressure would have been ample. 

I have not yet succeeded in making any general rules for sizes and capacities 
for air lift pumping. There is generally a surprise waiting for you, no matter 
what you do. There should be some particular relation of all the quantities con- 
cerned that would give the best results, and yet for a considerable variation either 
way, in submersion, and air pressure, the quantity of water will remain the same. 
The relation between the diameter of the discharge pipe and the velocity of water 
seems to be a delicate one. I should think that 5 feet per second would establish 
a good proportion. The air pipe must be large enough to minimize the friction 
loss. The initial air pressure? will, of course, be that due to the submersion, and 
will decrease after the discharge begins, until with a 3 to 2 submersion the pres- 
sure will correspond to a head of about one-half the submersion plus the lift. In 
flowing artesian wells, the best results seem to be obtained by giving deep sub- 
mersion, small air quantity and high pressure. 

Sand may be cleared from a well by filling the air reservoir with air at a 
high pressure, then suddenly releasing it, the air pipe having first been given quite 
a submersion. The sand comes out in masses and can be seen distinctly. In the 
illustration submitted herewith the column of water measured over 100 feet above 
the mouth of the well. It will be noted that about 20 feet above the mouth of the 




FIG. 245. 



USE. 643 

well there seems to be a general radiation in all directions from one center of the 
water sprays. It would seem that a bubble of compressed air had been carried 
up there and then suddenly expanded. The efficiency of the air lift will naturally 
increase directly in proportion to the temperature of the water. 

The air lift has a special field of usefulness and will scarcely be given over to 
much competition with other pumps. When a large quantity of water must be 
brought out of a small casing, no other method would be so satisfactory. If an 
artesian well fails to deliver to the proper point by a few feet, no other system 
could make it deliver its water so efficiently. For example, at Alvarado one of 
the large artesian wells refused by about two feet to flow into the general cache- 
ment basin; nothing could be done but to pump it, and it would have required a 
centrifugal pump capable of handling 1,000 gallons a minute to restore the re- 
quired quantity. A one-inch compressed air pipe inserted 155 feet into the well, 
and consuming 6 horse power of compressed air, stimulated the well to complete 
action. 

The plain open air pipe seems to be the best manner of ending the air pipe in 
the well, and whether it point up or down is not material. Dividing the air into 
minute bubbles by fine perforations seems not to do as well as the open pipe. I 
have compounded the air lift into several lifts, one discharging into the other, 
with fair results, but it would be better to discharge each section into an open 
tank and let the water dispose of its air bubbles. 

The greatest general efficiency of the system will become apparent under con- 
ditions where the number of wells that can be operated by an engine plant do not 
yield enough water without lowering the surface of the water too far. Let us say 
that normally the water stands at 20 feet from the ground, and in order to get the 
quantity from six wells they are lowered to 80 feet. By sinking perhaps six more 
wells some greater distance away, and the air-lifting all twelve, the pumping may 
be done at a head of only 40 feet. This would be possible, of course, with pumps, 
but not practical. In general and within pumping limits of 120 feet, I shall con- 
clude that from 50 to 60 per cent, efficiency is possible, but 30 to 40 will probably 
be nearer the average plant. 

Table 56 is from actual experiments made last year, and Table 57 gives 
some general requirements for air lift pumping which may prove useful. 

MOTOR-OPERATED PUMPS. 

This class consists of pumps belted or geared or direct connected to any kind 
of engine. There is no doubt that with Corliss engines, coupled directly to 
pumps, the mechanical efficiency is as high as 85 per cent. Let us take an example 
on this basis, using compound compression, and the engines being cross com- 
pound, and double reheated, to 300 feet, or 7-5 increase of volume. The comt)ar- 
ison of curve areas, Fig. 246, shows that an efficiency of 88 per cent, should te 
obtained. This, it must be understood, is for a station pump, where all propor- 
tions are specially designed for the one object in view. 

No account in any of my calculations is taken of reheating. The expense is 
small, and, I should think, might be taken as 5 per cent, of the economy, conse- 
quently this sum should be deducted from all of my reheat ig calculations. It 



644 



USE. 



costs practically the same to heat to 300 or 400 as to 200, provided the reheater is 
close to the motor, where it should be. The amount of air required by engines 
per horse power will vary from 25 to 5 per cent., according to the amount of re- 
heating and amount of expansion used. 

All admit that the loss in the compressed air problem is one of heat. The 
air is all there; none of it gets away. All admit that if this heat can be stored 




FIG. 246. — DIAGRAM OF COMPOUND DOUBLE REHEATED AIR MOTOR FOR PUMPING. 

and a sufficient quantity added to overcome leakage and clearance, we should get 
back our original expenditure, less, of course, the mechanical losses in the motor. 
Inasmuch as in compound compression to 90 pounds the temperatures need not 

TABLE 58. 



RECAPITULATION. 
90 Lbs. Air Pressure on Main. 



Kind op Pump. 



Direct Acting Simple 

Direct Acting Simple 300 reheated 

Direct Acting Compound Water reheated 

Direct Acting Compound ] Cylinder Heated 300 
Direct Actiog Compound 2 Cylinder Heated 300 

Direct Acting Triple 3 Cylinder Heated 300 

Direct Acting Triple 3 Cylinder Healed 400 

Plain Displacement 

Wheeler Displacement 

Mnliiple Displace^ient 

Harris Displacement 

Merrill Displacement 

Camming System 

Compound Motor Pumps 

Direct Acting Triple Water Heated 

Pohle Air Lift 



Foot 
Gallons. 



135 
180 
332 
280 
326 
383 
444 
175 



^J^^V^y i Efficiency 



19 
24 
32 
40 
46 
54 
63 
22 



20 
28 
375 
46 
53 
62 
72 
25 



34^ for 34 lbs. pressure. 



320 

60 
175 

35 

50 to 
300 

30 



40 

to 70^ 
I 22 
to 70^ 



42 



46 
25 



48 



to 60^ heads less 



than 200 feet. 



USE. 645 

exceed 225 degrees at any time, what is there to hinder our returning this and 
much more besides, when we have 500 degrees at our service? I have used 430 
degrees in a Corliss motor with excellent results, and believe another 100 degrees 
could have been added. The whole question is one of temperature, and the suc- 
cessful solution lies in special and intelligent adaptation of the forces at our ser- 
vice. Too many have condemned compressed air without a hearing, and I hope 
these remarks may stimulate some one to give special attention to the pump prob- 
lem and give us some pumps worthy of the atmosphere which they now so gen- 
erously use. 

In conclusion, it may be stated that I do not wish to be understood as giving 
absolute values to the quantities mentioned in this paper. Others may find in 
their experience that I may have allowed too little or too much for mechanical 
efficiencies, or that I have assumed too high a standard pressure. This does not 
interfere with the comparative values of the various systems, which is the real 
point toward which I have desired to direct your attention. 



Editor of "Compressed Air" : — 

On reading an article in the last number of your useful little journal, 
entitled "Pumping by Compressed Air," I was somewhat surprised to see that you 
attributed the working of the Pohle Air Lift Pump and its kind to the air acting 
as a piston, forcing the water in sections to a higher elevation, on the same prin- 
ciple as that of a common chain and button pump. 

I believe this is the wrong conception of pumping water under the condi- 
tions in question. 

I have had occasion to experiment very largely in this direction, and before 
active work I adopted a different theory that was fully proven by later practice. 

This was that the air, mingling with the water after its discharge from the 
air pipe, lightened the water to the extent of its impregnation, and so creating a 
mixture whose equilibrium can only be established with the solid columns of 
water surrounding it by its raising higher. 

This height will be proportionate to the amount of air in volume contained 
in the water. 

This theory can be nicely illustrated by bending a glass tube in the shape of 
a letter "U" and placing soap-suds in one leg and water In the other; it will be 
seen that the lighter suds will rise to a height compared to the solid water in pro- 
portion as they weigh in bulk. 

Upon this theory I have obtained the best results in lifting water. 

I first, reasoned that if this was the correct theory, the slower the air tra- 
veled upward the longer I would have it to do the displacement act, and I accord- 
ingly constructed a jet on the end of the air pipe similar to the opening in a com- 
mon steam-whistle, so that I would divide the air into as small particles as possi- 
ble, knowing well that it required a longer time for a small bubble to travel upward 
than it did for a larger one. • • 

The results attained fully justified my theory. 



646 



USE. 



Comparison with an air nozzle of the Pohle type, with the same amount of 
opening, gave a difference of lo per cent, in favor of my construction. 

I will also say that there was no eduction pipe used; the air pipe was sim- 
ply lowered down in the 8-inch well to a depth of i6o feet, and the water was 
lifted about 30 feet. eugene biddisen. 

The Portland Gold Mining Co., 
Vicfor, Colo., July 30, '96. 



LIFTING WATER BY COMPRESSED AIR. 

It is only within recent years that moderately deep well pumping by means 
of compressed air has become at all common. Under favorable conditions the 
system possesses several decided advantages over all other methods. Among 




FIG. 247. — LIFTING WATER BY COMPRESSED AIR. — PROFILE OF POINT PLEASANT 

WATER WORKS. 



these may be mentioned the absence of all moving parts, in the way of valves, 
pistons, rods and packings necessarily located a hundred feet, or several times 
that distance, down in a well where they are difficult of access at all times, and 
which sooner or later become worn or broken, when they must be taken out to 
be repaired. All these parts are done away with in the air lift system. Nor 
does sand or grit affect the working of this system in any manner. There is not 
a valve or attachment of any sort whatever placed in the well, simply two ordi- 
nary pipes. The necessary machinery is located in the engine room, where it is 
readily accessible at all times. 

The object of this article is chiefly to illustrate two quite novel features 
in the adaptation of the system to pumping water from muddy streams flowing 
in deep channels. To make this entirely clear, a brief description of the air lift 
system will not be out of place. 



First, there must be an air compressor — that is, an engine that condenses 
or compresses air to the necessary pressure — discharging into a metal tank called 
the air receiver. To this a pressure gauge and safety or escape valve are 
attached, which are identical in all respects to those commonly found on steam 
boilers. From the receiver a small gas pipe is led to the well and thence down- 
ward to near the bottom, where it enters the water discharge pipe; or a series 
of air conducting pipes may be attached to the receiver and connected to a series 
of wells situated closely together or remotely at varying distances. 

Suspended in each well is a water discharge or conducting pipe, also 
reaching nearly to the bottom or as far down as may be desired. This pipe may 
be of any desired size, but is usually several times that of the air pipe in the pro- 
portion of 4 diameters to i, or 4 to i>4> depending on circumstances. 

The air pipe is usually arranged to follow closely along and outside the 
discharge pipe to its lowest extremity, where it is fitted with a return bend and 
nipple, as shown in illustration, Fig. 248. It will be observed that the air from the 
receiver is thereby discharged upward directly into the bottom of the water 
discharge pipe. It has been the practice of some engineers to attach a brass 
nozzle at the extremity of the air pipe. Various styles of these are offered, some 
being patented, for which the makers claim decided advantage; but it has been 
ascertained that in this case nothing is better than something (anything). A 
free discharge of air directly into the foot of the suspended discharge pipe is all 
that is necessary. 

The effect of discharging highly compressed air into the bottom of the 
discharge pipe is to displace some of the water in it, lessening the gravity of 
what remains until overcome by the greater pressure of the solid column of water 
outside of the discharge pipe within the well. Both the air and water in the sus- 
pended pipe are forced upward by this resisting pressure and discharged at the 
top of the well or outlet of the suspended pipe. It will therefore be apparent that 
as long as there is sufficient depth and flow of water into the well to constantly 
refill the discharge pipe, and air is supplied to reduce the gravity of that in the 
discharge pipe, the operation, as described, will continue. 

There is, however, one important condition to the successful operation of 
the air lift system. There must always be ample depth of water in the well to 
insure sufficient resistance at the foot of the discharge pipe to force the lightened 
column inside the discharge to the top of the well. This is termed "submer- 
gence." 

Well informed engineers who have made a study of the system say the 
submergence should be 50 to 60 per cent. By this is meant 50 or 60 feet of water 
to each 100 feet depth of total lift. That is, if the well is, say, 200 feet deep, and 
it is desired to discharge the water into a tank situated 50 feet above the top of 
the well, there must be not less than 125 feet (50 per cent, of 250) to 150 feet (60 
per cent.) of water in the well at all times. A less depth would probably render 
the system useless, as the resisting pressure would be insufficient. 

It is customary to discharge the water directly into a tank or receiving 
basin situated immediately above or closely alongside of the well, with very 
short, if any, lateral conveying pipes. 

During the past 12 months there has been constructed at Point Pleasant, 
W, Va., on the bank of the Ohio River, a water works employing the air lift 



648 



USE. 



system to obtain water from the river, in which this practice was radically 
changed. 

All the machinery was located above the highest known flood line, which 
is over 60 feet above the lowest river stage (U. S. zero gauge). The franchise 
granted the water company was for a combined water and electric light plant, 




FIG. 248.— AIR LIFT. 



USE. 649 

and specified that water was to be taken from the Ohio River, The most desirable 
site obtainable for the works was about a mile above the town, but the Ohio 
River Railroad tracks at this point were too close to the river bank to permit the 
erection of the works on the river side of the railroad. The power and pumping 
liouse had therefore to be located about 200 feet distant from the top of the 
bank, about 400 feet laterally from low water point in the river and (i'] feet above 
it, as shown in Fig. 247. 

To have constructed a pumping well of sufficient depth and size to accom- 
modate pumps to draw water from the river channel at zero stage and a tunnel to 
the river would have made the cost of the works so great that sufficient capital 
could not have been secured to erect them. Some other and less expensive sys- 
tem had to be adopted. Manufacturers of water works machinery were consulted 
and various plans and systems considered. Finally it was determined to adopt 
the air lift system, and a hydraulic engineer was employed to make specifica- 
tions and plans. He proved so unreliable or ignorant of what was required that 
his services were dispensed with. 

The Howell & Shanklin Construction Company, of Charleston, W. Va., 
were then invited to submit plans and specifications. These were promptly 
adopted, and a contract was made with them to erect the works entire, which 
were completed to the last detail just as planned and specified by them. 

The use of the air lift system would require wells deep enough to obtain a 
submergence sufficient to overcome the 67 feet bank lift, plus the depth of the 
wells and friction of about 500 feet of discharge pipe from the wells to the 
receiving basin placed obliquely up the river bank. Just here the algebraical x in 
the problem was found. 

At a meeting of the Central States Water Works Association, held in Cin- 
cinnati, September, 1899, the writer sought information regarding the application 
of the air lift system to such situations. 

When it was stated that it was the intention to take water from wells sunk 
in the channel of the Ohio River and discharge it into a basin situated as 
described, the discovery was made that the problem was not only new, but of very 
doubtful solution. There was no reliable information obtainable from that 
source on this particular feature of the enterprise. 

Later, an engineer, representing one of the oldest builders of air com- 
pressors and who has had many years' experience in this line, after a personal 
examination reported the situation to his firm, who declined to furnish machinery 
with any guarantee of success because of the probability that when the air 
reached the sloping pipe up the bank it would pass the water and escape, the 
water returning to the wells. 

Nothing daunted, the contractors proceeded with the works. Presuming 
that the wells would always be full if located and sunk at low water line, it was 
decided to make them no feet deep. The calculation was based on 60 per cent, 
submergence as being ample to overcome both lift and friction. 



650 



USE. 



Fig. 247 is an exact copy of a profile of the river bank made by the city 
engineer of Point Pleasant, and clearly shows the difficulty encountered. Careful 
soundings of the river channel were made, and it was found that there were 
several feet depth of sand and gravel forming the river bottom at this point. 
Well casing 10 inches inside diameter was driven to the rock, about 40 feet in 
depth. This casing was perforated with hundreds of ^-inch holes, commencing 
at about 10 feet from the top, and extending about 10 feet downward. After the 
lo-inch casings were in place lo-inch holes were drilled in the underlying rock 
116 feet deep and cased 8 inches inside diameter from bottom to top. This 
casing was also perforated similarly to the outer one, only the holes were larger 
— 5-16 inch. The space between the two casings was tightly calked at the top 
to prevent water entering the wells at this point. Four-inch discharge pipes and 




FIG. 249. — CAP AND GLAND FOR WELL HEAD. 



i^-inch air pipes were properly fitted and suspended in each of the wells, with 
their extremities no feet below the top of the 8-inch casing. 

Both pipes were suspended from a water tight cap, Fig. 249, resting on the 
top of the 8-inch casing shown in Fig. 248. It will be observed that no water can 
enter these wells except through the perforations in the casings, which are 10 
feet to 20 feet below the flowing water in the river. None can enter at the 
bottom. It was the desire to allow the river water to enter the wells only through 
the perforations after having passed through the strand strata mentioned, which 
would serve as a filter. Before proceeding further, I wish to state that this 
feature has proved successful beyond expectation. However muddy the river 
may be, the water taken from the wells is bright and sparkling at all times. 

Just when the wells were completed and the pipes in place, and extended 
up the sloping river bank a short distance, the river rose over the wells. The 
pump and air compressor builders were weeks behind promised delivery, and for 



USE. 651 

two months the wells stool unused as described. In the mean time, the reservoir, 
receiving basin and power house were completed and the work advanced as fast 
as possible. Just as soon as the air compressor was in place the air pipes were 
connected up and the wells tested before the discharges were extended to the 
receiving basin. One well was found with a deposit of sand in the bottom reach- 
ing 5 feet above the foot of the discharge pipe. Several unsuccessful efforts were 
made to force air into this well. The river having receded, the air pipe was 
disconnected at the top of the well and a ^-inch gas pipe coupled and lowered. 
It stopped 5 feet from the bottom. It was churned a few minutes and soon went 
down the remaining 5 feet. Again the air pipe was coupled and the air pressure 
increased to 90 pounds per square inch. The effect was almost startling, but 
gratifying. The obstruction was cleared out very quickly. No other system 
of pumping could possibly have accomplished the clearing out of this well of the 
sand deposit. 

The discharge and air pipes to each well are independent. That is, each 
well has a separate discharge to the receiving basin and a separate air pipe from 
the receiver. These are carefully graded and are not exposed at any point except 
where the discharges pass through the top of the walls of the receiving basin, 
and have open discharge. 

The power house is a good substantial brick structure immediately along- 
side the Ohio River Railroad. It contains the steam boilers, a 200 horse-power 
Corliss engine, electric dynamos, air compressor and forcing pump. These are 
all placed on separate and substantial foundations. No machinery is attached to 
the walls of the building. All the machinery, both pumping and electric, is belt 
driven from friction clutch pulleys on a line shaft. All the machinery is very 
substantial and capable of performing its duty without strain. The air com- 
pressor is 14 inches diameter by 18 inches stroke, with mechanically operated 
valves. It is speeded to 96 revolutions, and has a capacity of 312 cubic feet of 
free air per minute. The required working pressure is from 45 to 50 pounds, 
varying with different river levels. 

The discharge of water is not constant, however, but irregular or inter- 
mittent, as though the air and water formed alternate strata or volumes within 
the discharge pipes. It varies with the depth of water in the river, ranging 
from I volume of water to 8 volumes of free air to i to 6. As the river is con- 
stantly rising and falling and frequently is 25 to 40 feet deep over the wells, the 
pressure on the sand surrounding the wells is constantly changing and affects 
the capacity of them as well as the necessary air pressure to pump them. 

The reservoir is situated about i^ miles distant and at 225 feet elevation. 
It is built of vitrified paving brick laid in Portland cement with 18-inch concrete 
bottom and roofed over with slate. Water is taken from the receiving basin 
by belt driven triplex outside packed plunger pumps, 9 inches diameter by 12- 
inch stroke, operated at Z7 revolutions per minute, delivering about 22,000 gallons 
per hour. 



652 USE. 

As there is no demand in the town for electric current during the day, 
the works are operated at night only. Usually the air compressor is operated 
one night, and the following night the forcing pumps. The water received the 
previous night in the settling or receiving basin has about 12 hours to become 
cleared of any sand brought with it from the wells before going to the reservoir. 
This basin has a capacity of about 225,000 gallons; the reservoir about three 
times this quantity. The construction of the receiving basin is the same as the 
reservoir. The engine has ample power to operate all the machinery at the 
same time. Two men only are required to attend the combined plant. The 
entire plant, including power house, lot, reservoir site, rights of way, mains, 
hydrants, wells, lines, machinery, arc light, all included, cost $55,000. In addi- 
tion to the public and private consumption of water, two busy railroads are 
consumers. All customers are served by meter and therefore there is practically 
no waste. 

There can be no doubt that water taken by air in this manner is purified 
to some extent, the admixture of air serving to oxidize and destroy organic 
matter. Samples of the water taken last January are still bright and sparkling, 
have no odor and remain apparently unchanged. There probably is not 
another town of 5,000 inhabitants in the country that has a better or more 
complete combined water and light works. Certainly there is not another town 
of any size on the banks of the Ohio River from Pittsburgh to Cairo that has 
better water, if as good. 

The works have been in constant operation since January last and have 
been visited by many interested parties. The system demonstrated at Point 
Pleasant will beyond doubt be repeated elsewhere. That it is regarded as a 
paying enterprise we have but to repeat the president's statement made to the 
writer a week ago, "There is no stock for sale, and not a single share was sold 
at less than par." The pump and compressor were built by the Stillwell-Bierce 
& Smith-Vaile Company, of Dayton, Ohio. 

What has been accomplished at Point Pleasant can be done at hundreds 
of other small towns similarly situated where there is no water works. Here it 
has been demonstrated that bright, sparkling water can be obtained from a 
muddy, filthy stream without the use of chemicals or mechanical filters. 

Just use the filter nature has so abundantly supplied at the bottom of such 
streams, and by proper arrangement of the pumping system combined with an 
electric lighting system, thus economizing the operating expenses to a minimum, 
establish first-class water and electric service on a paying basis when neither 
separately would pay operating expenses. 

The air lift system is undoubtedly the simplest as well as the best of all 
known methods of serving such towns with good water. Nor is the system 
less applicable to larger towns, as well as to factory and domestic supply. 

Artesian wells, or wells supplied from land sources, generally yield hard 
water or water highly charged with mineral salts. The water at Point Pleasant 
is soft, pleasant and wholesome. The railway companies using it speak very 
highly of it. It is simply Ohio River water freed of filth and all objectionable 
matter that renders it so disgusting at many towns along the stream. 

Clark Howell, in The Metal Worker, 



USE. 
PUMPING WATER BY AIR. 



653 



While much has been said of the Air Lift and its advantages over other 
systems of pumping water, it is not always clearly understood what such an outfit 
consists of, and we therefore give the following illustration. 




FIG. 250. 









f 
$ 



If 



J 



As will be seen, the outfit includes an air compressor, which may be either 
steam-actuated or belt-driven; an air receiver to equalize the flow of air to the 
well, and the piping in the well. 

The compressor is located in the engine room, where it is always under 
the eyes of the engineer ; and as compressed air can be conveyed for miles with- 
out loss, the well may be any distance away. 

The air receiver may be placed either inside or outside of the engine room, 
whichever is preferable. If located outside, the pressure gauge can be attached 
to one of the walls of the engine room. 

The method of piping a well differs, we are told, according to its general 
conditions and the quantity of water to be pumped. No two wells are alike, and 
consequently the method of piping which might be applied to one would be un- 
suited to another. This, however, is not very generally understood. 

In the accompanying illustration the method of piping consists of using 
the well casing as the water discharge pipe and simply putting a small air pipe 
down in the well, with a special device attached at the bottom through which the 
air escapes. Another method consists of placing the air and water pipe alongside 
of one another in the well, connecting them at the bottom with an end piece. 
A third method places the water discharge pipe into the well, the air passing 
down through the annular space between the well casing and the water pipe. 
While each is different from the other, yet the principle as patented by the lale 
Dr. J. G. Pohle is the same — i. e., the water is raised by compressed air. 

The advantages of the air lift system appear numerous. At the Fort Madi- 
son, la.. Water Works, it pumps 3,000,000 gallons of water a day from a well 12" 
in diameter and only 100 ft. deep. At the Charleston, S. C., Water Works about 
300 tons of quicksand was raised with the water. This would not have been 
possible with any other pump. At the Ocean Grove, N. J., Water Works twenty 
wells are operated by one compressor; the wells are widely scattered and some 



654 USE. 



of them are almost half a mile away from the engine room. At the Asbury 
Park, N. J., Water Works it helps to purify the water by precipitating the iron 
with which it is strongly impregnated. 



COMPRESSED AIR FOR SUPPLYING WATER. 



By C. W. Wiles, Siipt., Delaware, Ohio. 

The system of supplying water from deep wells by an air lift or air com- 
pressor, is one not in general use in this country, and has to some extent been an 
experiment; but the results have justified the opinion that for moderately flowing 
wells, or wells having a head not more than 25 or 30 feet below the surface, being 
too low to draw from by ordinary suction pumps, the application of compressed 
air at some distance below the top has largely increased the supply of water. 

The water supply of The Delaware Water Company, at Delaware, Ohio, is 
taken from a circular well 25 feet in diameter, brick lined, and 24 feet deep, with 
an excavation of 5 feet in the rock. Connected with well is a gallery of an average 
depth of 18 feet down to the rock, 295 feet long by 7 feet wide, covered with slabs 
of stone and earth, by which water is gathered to further supply the well. With 
plenty of water in the gravel bottom this well furnished in abundant supply of 
good water for the city, but in the extreme dry season of 1895 the amount of 
water was so limited that steps were taken for further supply. 

A 6-inch well was bored through the gravel bottom 20 feet, and cased ; then 
through the solid rock of various kinds to a depth of 255 feet in all, a continuous 
flow of water was developed, to the amount of 65,000 gallons in 24 hours. This 
not being sufficient for the demand, an Ingersoll-Sergeant Air Compressor, 
Straight Line Class "A," with steam cylinder 12 inches in diameter, by 14 inch 
stroke, air cylinder I2^4 inches in diameter by 14-inch stroke, 116 to 155 revolu- 
tions per minute, capable of furnishing 213 to 285 cubic feet of air per minute, at 
50 to 80 lbs. pressure, was installed ; a receiver, 36-inch diameter, 6 feet high con- 
necting from which a 3-inch pipe conducted the air to the well; about 100 feet 
from the top of the well a i^-inch pipe takes the air 144 feet down into the well, 
ending in an inverted funnel to deflect the air upwards. 

With 40 lbs. of air pressure at the receiver the flow of the wells is increased 
to 500 gallons per minute ; this flow has been maintained at different times for 14 
hours continuously without any apparent diminution of the flow, the well requir- 
ing from 60 to 70 minutes to recover its natural flow after the air is romoved. 

The flow of water from this well is conducted direct to the large circular 
well from which it is taken by the pumps. 

The power required to develop this flow is 15 to 25 horse power, and is 
taken from the same boiler that operates the pumps, with a small addition to the 
amount of fuel. 

This method has proven very satisfactory and has given excellent results. 

The application of this method of raising water on a larger scale is in opera- 
tion at Indianapolis, Ind., where from some 27 wells of 8 inches to 10 inches in 
diameter, 18,000,000 gallons of water per day is supplied to the city. A similar 
plant to the one at Delaware, Ohio, is in operation at LaGrange, 111. 



USE. 655 

AIR JET PUMPS. 

During a recent trip to the Missouri-Kansas zinc mining district I made 
quite a study of pumps, and the idea of using air in this mine pumping service 
occurred to me, and abides with me still. I started in as a matter of curiosity, 
for there is a prevalence of curious old walking beam pumps in that locality, but 
in studying the causes for the existence of this old curious pump in such numbers 
I came to study the requirements of the mines, which lead to an impression that 
air might enter as a factor of some magnitude in this industry. The mine depth 
will average about one hundred feet — varying from forty to two hundred — and 
quite a variety of pumps are in use. The old walking-beam pump is nothing but 
a straight pipe with a working barrel and piston near the bottom end, and it has 
peculiar advantages during the process of shaft sinking which accounts largely 
for its continued use. It is provided with a slip joint below the working barrel, 
which can be extended as the shaft deepens — to about twelve feet — and then there 
is only a top joint to screw on Wlien the operation may be repeated. Also, it is 
very little in the way — only a pipe standing down in a corner of the shafts— and 
it is not so liable to get damaged during the firing of a blast, for it presents no 
working points to view, and a few pieces of plank stood up around it is all that is 
required in the way of protection. It seems that no modern pump has yet been 
devised that will meet such requirements and the result is that the old lift pump 
is put in for shaft sinking, and usually remains there for continuous service. 

Some years ago there grew up among some southwestern sawmills a prac- 
tice of using air for pumping under some peculiar conditions. There was plenty 
of water to be had — under ground — and the easiest, quickest and cheapest way to 
get it was to drive pipes, or bore wells. The depth of the water under ground 
was such that to suck it out with a surface pump was not satisfactory, and to 
put a pump, down to the water called for the digging of a shaft. A builder of 
air compressors conceived the idea of running an air pipe down inside of the 
well or driven pipe and forcing the water out with compressed air — and it worked 
to the general satisfaction of the users. 

Now, when I got to studying this mine pump question that using of com- 
pressed air to drive water up a pipe came to my mind and I began to make 
inquiries concerning its use— if it had been tried. It looked as if this ought to 
simplify the thing, even beyond that of the old walking-beam pump, but I was 
turned down in my ideas at first start by the theory that it requires something 
like sixty per cent, of the well to be filled with water before the air service could 
be made to do the work, or, in other words, if one wanted to pump water from a 
forty foot mine he would have to have a well pipe a hundred feet deep. Of 
course I knew a little something about this matter, and could understand that it 
would require a little water at the bottom of the well, but I did not like being 
stumped with the idea in such strong terms. I suggested that the pumping 
service could be divided into relays up along the pipe, and before leaving the 
territory I found that there was something being done in that line. A man was 
driving water out of a mine with air and said he could handle it all right with a 
depth of ten feet in the bottom of his pipe. 1 think his well was something like 
a hundred feet deep, and the way he did it was something like this : He had an 



656 









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USE. 657 

air jet at the very bottom of the pipe— piped down inside the main pipe— and 
about half way up he had another that would open when the water reached that 
point going up the pipe, and this one would then take up the burden of the work. 
The idea that is still clinging to me is something after this plan ; it seems 
to me that a series of air jets could be so arranged, with a line of small piping 
inside the main water pipe, that water could be lifted from any depth, and I offer 
the idea for study and experiment. A pump after this plan would be even less 
in the way, and more convenient in shaft sinking than the old lift pump that has 
clung on so long, but whether the idea is practical or not I am not able to say 
just now, and can only offer the matter herein as a subject for consideration. 
The valves along the line would seem to require some automatic appliance for 
their operation, etc., but it looks plausible. Taylor. 

The contribution above appears to be in the line of compounding what is 
known of the Pohle Air Lift Pump which ordinarily lifts the water in one stage. 
The idea has been suggested before and we show a sketch outlining the method. 
This system has been adopted somewhere, but we do not know just where, and 
are not in a position to say anything as to its economy. It can readily be seen 
where it would have advantage over the old Cornish or walking-beam pump, as 
it would not require packing or replacing of parts. The Pohle Air Lift system 
having none of these and consisting simply of two properly proportioned pipes 
without valves or barrels instead of the Cornish or walking-beam type of pump. 
An ordinary sinking pump of the Cameron type is frequently used and operated 
with compressed air. Such a pump is subject to wear because of grit or acid in 
the water just as is the Cornish pump. The Air Lift possesses many advantages 
in pumping water where the conditions admit its use. 



San Francisco, Cal., July 21, 1899. 
Editor Compressed Air : 

I notice your quotation of an inquiry by J. T. B., and reply by the National 
Engineer, in your July number regarding the operation of a proposed air lift. 
I do not know who J. T. B. may be, but if he follows the advice given he will 
fail to get water. Here are the corrections that should be made to the reply: 

The well will be better without the 5" casing advired. The well casing 
6", is better, by the difference in friction. 

The flow will never be steady, but intermittent. 

With the submergence given (125') the supply of air will have to be 
between 14 and 15 times the water flown. 

The reservoir pressure will be the submergence + friction of air pipe, i. e., 
125 lbs., X .434 + say, 5 lbs. or less than 60 lbs. It will take 6 lbs. to start it. 

If the well is operated singly, no receiver is necessary or advisable. 

Finally, the air will operate with an efficiency less than 20 per cent. This 
efficiency is entirely independent of compressor efficiency. G. S. D. 



658 



USE. 
WATER WORKS AT DIXON, ILL. 



The water supply at Dixon, 111., is derived from three artesian wells, seven 
inches in diameter, and from 1,630 to 1,800 feet deep. Two of the wells flow into 
a reservoir of 500,000 gallons capacity. When the reservoir is empty, these two 
wells flow at the rate of 566 gallons per minute, but when it is full and the well 
tubing submerged, the flow drops to 123 gallons per minute. 

When this amount of water, together with the flow of the third well, is 
sufficient for ordinary requirements, it was not adequate during the summer 
months, and to increase the supply at a minimum expense, it was decided to in- 
stall the air lift system. 

The air compressing plant was furnished by the Ingersoll-Sergeant Drill 




FIG. 252. — PUMPING PLANT AT DIXON, ILL. 

Co., of New York, and included a Class "A" Piston Inlet Air Compressor, having 
14" diameter steam cylinder, 16^" diameter air cylinder with 18" stroke. 

At a recent test of the two wells flowing into the reservoir, they were able 
to secure 1,261 gallons of water per minute by the air lift, with the reservoir 
empty, and 1,212 gallons per minute with the reservoir full and the well tubing 
submerged. This increase is equivalent to almost ten times the flow of the wells 
under the latter conditions. The compressor is operated at only 56 revolutions per 
minute. 

The accompanying illustration shows the engine room at the water works 
station. The large Gordon & Maxwell pumping engine shown in the illustra- 
tion has a capacity of 2,500,000 gallons in 24 hours, while the small compressor to 
the left, running at only 56 revolutions per minute, is pumping nearly four-fifths 
of this amount from only two wells. If connected to all three wells, the com- 
pressor would readily deliver into the reservoir all the water the large pumping 
engine could possibly handle. 



i 



r 



USE. 659 

SOME FIGURES ON THE COST OF PUMPING WITH THE POHLE 

AIR LIFT. 

The Pohle Air Lift Pump is one of the most valuable of the many applica- 
tions of compressed air, and though comparatively new, its developments have 
been rapid. It has been applied widely to the raising of sub-surface waters which 
lie below the reach of suction pumps, and in some instances it has replaced the 
suction pump where the conditions did not imperatively call for the air lift 
system, because of its many advantages. Many manufacturers located along the 
banks of rivers, lakes, etc., who are now obtaining their water by means of crude 
direct acting steam pumps or through the city or village pumping station, can 
reduce the cost of the water supply materially through the use of a pneumatic 
pumping plant. There are few figures available as to the cost of pumping under 
this system, and the following may be of interest. 

We will assume a manufacturing plant, say 1,000 feet away from the best 
location for wells, or from a surface body of water. In the latter case, the 
pneumatic displacement pump may be used, hung from piles or otherwise sus- 
pended in the water. The air lift may be used by drilling wells close to the edge 
of the water, or a better quality of water in sufficient volume is often obtainable 
from driven wells some distance away. 

With the air lift the plan of pumping involves the use of an air compressor 
located where the expense of attendance is least; an air receiver adjacent to thib 
compressor; a pipe line for conveying the air from the receiver to the wells; a 
number of wells drilled to a depth proportionate to the height of lift and the 
depth of the water strata below the surface; air and water pipes running down 
inside these wells representing the pumping apparatus proper; a tank located 
close to the wells and at such height that the water flows by gravity to the point 
of consumption through a distributing system of pipes carried beneath the reach 
of frost. 

In many cases the introduction of the air lift may be effected at little ex- 
pense, often involving the purchase only of an air compressor, a receiver and a 
small amount of pipe, but in the following it is proposed to estimate on a basis 
which will cover the greatest amount of expense likely to be incurred with a view 
of showing particularly that the interest and depreciation charges under the most 
extreme conditions are not under any circumstances likely to develop into formid- 
able figures. The following figures are all approximate and are intended to be 
in all items well on the safe side : 

Estimated cost of Air Lift Plant to raise 1,500,000 Gallons 
per Twenty Hours, or 1,250 gallons per minute. Total lift, 
seventy-five feet. 
Duplex air compressor complete ready for foundation and piping, 

estimated $2,500.00 

Air receiver 13500 

85 H. P. of boiler with feed pumps, etc., bricked up and ready for use, 

including building and value of ground so occupied, at $15.00 per H. P. 1,275.00 
Tank, say 19,000 gallons capacity (15' x 14' 6") including suitable timber 
frame work to bring tank 75 feet above water level 300.0Q 



66o ' USE. 

Two 12 inch wells, each 135 feet deep, cased, at $4.00 per foot 1,080.00 

450 feet jYs inch light casing (water discharge pipe) at 60 c. per foot in 

place 270.00 

500 feet of 3 inch casing (air pipe in wells) at 15 c. per foot in place. .. 75.00 
1,000 feet of 4 inch air line from receiver to wells at 23 c. per foot in 

place 230.00 

1,250 feet of 12, 10 and 8 inch cast iron distributing main, leaded joints, 
from tank to works, laid below frost (air line laid in same trench) 

at $1.00 per foot 1,250.00 

All pipe and fittings not covered in the above estimate, say 150.00 

Compressor, receiver and tank foundation, say 18,000 brick laid in 

cement at $12.00 per 1,000 216.00 

Excavation for foundations, say 75 cubic yards, at 33 1-3 c. per yard. . 25.00 
Allowance for ground space and buildings occupied by compressor and 

receiver 400.00 

Special automatic, governing mechanism 75-00 

Erecting and starting expenses of compressor plant 75-00 

Freights 100.00 

Royalty 400.00 

Contingencies, sundries, etc 164.00 

Total estimated cost of complete plant ready to run as above $8,750.00 

As before stated, this is intended to include everything which may be 
considered as a legitimate expense in this connection. In many cases the build- 
ings, boilers, tanks, wells, pipe lines, ground space and other items do not repre- 
sent a present expense, being already on the ground. From the above figures we 
may estimate the cost of operation as follows: 

COST OF OPERATION. 

Engineer, double shift, at $2.25 per day, $4.50; 1-5 time chargeable to 

pumping plant, per day $ .go 

Fireman, double shift, at $1.75 per day, $3.50, on the basis of one man re- 
quired for each 250 H. P. of boiler for 85 H. P., per day 1.19 

Fuel, 85 H. P., 20 hours, say 4^ tons at $2.00 per ton, per day 8.50 

Oil, waste and sundries, say .60 

Interest on investment of $8,750.00 at 5%, figuring eleven 25-day months 

or 275 working days per year, per day l.pi 

Deterioration, covering sinking fund, repairs, etc., providing for re- 
newal of complete plant every ten years, same basis as interest but 

10% per day 2.i8 

Insurance and taxes i % as above, per day .32 

Total estimated cost of pumping 1,500,000 gallons per day, 75 feet high 
under the above conditions 16.60 

Cost of each 1,000 gallons ($16.60 + 1,500), $0.01107. 
Kent, quoting the National Meter Co. as authority, gives the cost of water 
in the states as follows: 



USE. 66i 

Average minimum price per i,ooo gallons in 163 places, .094. 
Average maximum price per 1,000 gallons in 163 places, .28. 
With extremes ranging from 2^/2 c. to $1.00 per 1,000 gallons. 

As a usual thing, the water rate in most manufacturing cities in the Cen- 
tral States runs in the neighborhood of 8 c. to 10 c. per 1,000 gallons supplied. 
In some of the larger Eastern cities it runs up to 12^ c, and even higher for 
manufacturers, and in some cities of the second and third class goes as low as 
5 c. per 1,000 gallons. At 5 c. per 1,000 gallons, the yearly water bill on the 
above basis amounts to $10,625.00. 

And at the figure given above, 

01 107 4.566.37 



A yearly saving on the above basis of $6,058.63 

This equals a profit of 69 1-5% on the estimated investment of $8,750.00, 
or is the same as a dividend of 20% on an investment of $30,293.15. With the 
actual cost of the plant less than is figured above, as it would really be in the 
majority of cases, the saving would show still better. In many cases the opera- 
tion of the plant does not involve the extra expense of engineer and fireman, 
and these items may be deducted. In other instances the fuel cost, either through 
the use of high duty air compressors or through lower cost of coal, may amount 
to much less. The only other items which amount to much are those of interest 
and deterioration, and we have already seen that these have been taken on the 
outside extreme. In a plant pumping about 3,000,000 gallons per 20 hours 75 
feet high, where the cost of the fuel delivered is 85 c. per ton, but the other 
expenses are figured even more liberally than is shown by the above estimate, the 
cost per 1,000 gallons is about, .0084 cents. 

And in the same case, but pumping 50 feet high, about .006 cents. 

In another case involving the handling of about 15,000,000 gallons of water 
30 feet high every 24 hours, using compound condensing compressors, and with 
coal at $2.00 per ton, other figures being estimated on a very generous basis, the 
cost nets about $2.50 per million gallons, or about 2}/^ mills per 1,000 gallons. 
Jn many cases a belt compressor may be used, bringing the under-loaded fac- 
tory engine up to an economical load without involving any extra expense for 
attendance or fuel. Such plants can after be put in at comparatively little ex- 
pense and will frequently pay for themselves several times over in the first year. 
The cost of pumping does not run very high per 1,000 gallons, even in the 
smaller plants, and when used on a large scale, the system compares very fav- 
orably indeed with the best of other methods. In some cases water of inferior 
quality is being used at a considerable disadvantage because of its accessibility. 
In one instance river water highly impregnated with sulphur coming from coal 
mines above, resulted in an expense of $5.00 to $8.00 per day from the grooving 
and pitting of rolls in a steel working establishment. The effect on the boilers 
was very bad and represented an important item of expense in repairs and extra 
fuel burned. In such a case as this, it might be well to go off even a mile to 
sink wells in some desirable location, the superior quality of the water so ob- 
tained reducing in many ways the cost of manufacture. Again, with a copious 



662 USE. 

and inexpensive water supply, condensers may be attached to the main engine 
resuhing in a saving of 20% to 30% of the whole fuel bill. In some instances 
deep well pumps have been thrown out and the air lift installed, primarily be- 
cause of the thorough aeration of the water resulting in throwing off most of the 
sulphur and other objectionable qualities. Where river or other surface water 
is good the wells may be drilled close to the edge, the water flowing down from 
the top of the wells, and the system automatically adjusts itself to any variation 
of the river level. In many cases where there is a heavy strata of sand or gravel 
level with the river bed, this strata may be used as a natural filter by placing the 
wells some distance away and the quality of the water much improved. 

Where a part of the water only is used at a high elevation about the works, 
it is an easy matter to put in a supplementary air lift taking its supply from the 
distributing main and raising it in a second or compound lift to the point de- 
sired, thus avoiding the expense of raising the whole volume of water to the full 
height. The compressed air may in many instances be used to great advantage 
for other purposes about the works. There are already some 70 or 80 different 
applications of compressed air in railroad machine shops, and there is hardly a 
manufacturing business of any kind in which the use of compressed air would 
not reduce materially the expense in some important departments. 

Properly installed, little care from a competent engineer is required. The 
compressor may be arranged to be regulated by the water consumption so that 
the fuel consumed is proportionate to the amount of water used, thus leaving 
little for the engineer to look after except to see that the oil cups are kept filled. 
In point of durability the air lift stands by itself. There is nothing about the 
two plain open-ended pipes in the well to require attention until they are 
rusted through. A good air compressor requires no more expense in this direc- 
tion than any good steam engine. Using steam hot from the boilers with an 
economical rate of expansion the condensation is reduced to a minimum. It is 
a common sight to see a long line of steam pipes running down to a direct acting 
pump a considerable distance from the boiler. Authorities estimate that with 
fuel at $2.00 per ton, every 2" pipe uncovered costs Jfi.oo per year for condensa- 
tion. With air there is no condensation. The direct actmg form of pumps re- 
ferred to frequently require from 175 to 200 lbs. of steam per H. P. per hour, 
while an economical air compressor does its work on 15 to 40 lbs., according to 
type. The common form of water pump frequently consumes 50% of its power 
overcoming its own friction. The friction of a good air compressor is usually 
down to 10%, and may run down to 5%. A careful study of the system will 
prove very interesting, and it will often be found that it pays well to use the air 
lift even in those exceptional cases where the cost of the water is not materially 
reduced because of the other incidental features in economy. 

As the figures given may create the impression that the cost of pumping 
with a small plant may run disproportionately high, we will investigate in that 
direction also. In most small plants an inexpensive belt or steam actuated com- 
pressor may be used, entailing no additional attendance expenses and no extra 
boiler, building, or tank investment, and in some cases, there would be no addi- 
tional cost for well, piping, etc. Excluding tank, boilers and building, but making 
proper allowance for well, piping, steam driven compressor, receiver, foundation, 



r 



USE. 663 



freights, erection, etc., assuming that the tank and well are close to the work, we 
find that for a plant to pump 175 gallons per minute, or 252,000 gallons per 24 
hours, 75' high, the total investment is not likely to exceed $1,500.00. The in- 
terest, deterioration, insurance and tax charges, as above, aggregating 16% net on 

this sum per day $ .87 

A proportionate allowance for fuel at $2.00 per ton, attendance, oil, etc., 
should not exceed per day 2.50 

Total cost of pumping 252,000 gallons per day $ 3>37 

Cost per 1,000 gallons 01 1-3 

Cost of this amount of water at 5 c. per 1,000 gallons, per year of 275 

days 3465-00 

And at i 1-3 c. per 1,000 gallons 924.00 

Net saving effected per year with a plant costing $1,500.00 $2,541.00 

or a dividend of 169% on the investment. Certainly one had better borrow the 
money, even at a high rate of interest if necessary, rather than neglect such a 
saving as this. In many instances a surprising saving may be effected when the 
water is now being obtained by means of deep well pumps or other similar appa- 
ratus by throwing the outfit aside and installing the more economical Air Lift 
System. 

GEORGE R. MURRAY. 



USE OF COMPRESSED AIR IN A SALT WELL. 

In the fall of 1897, Messrs. Nuttall and Hubbell of the Buckley & Douglas 
Co., Manistee, Mich., conceived the idea of making an application of compressed 
air to salt wells for the purpose of pumping the brine. By employing two ma- 
chines, an air pipe was sunk to a depth of from 900 to 1,000 feet, and the results 
were of a very satisfactory nature. The success of the method being assured, the 
Buckley & Douglas Company immediately ordered an Ingersoll-Sergeant air com- 
pressor and began preparations for putting in the new system. The compressor 
was set up and put in running order about the first of July of last year. It has a 
steam cylinder twenty inches in diameter, a low pressure air cylinder twenty-two 
inches in diameter, a high pressure air cylinder nine inches in diameter, all having 
a common stroke of twenty-four inches. With this machine running at eighty 
revolutions per minute, 840 feet of free air is admitted through the intake pipe, the 
large cylinder compressing it to a sixty-pound pressure. After passing through 
the pipes and cooling, the high pressure cylinder continues the compression until 
it has attained a pressure of between four and five hundred pounds, thereby 
reducing 840 cubic feet to a volume of 30 cubic feet at a pressure of 840 lbs. to the 
square inch ; each cubic foot of compressed air contains as a result, 28 cubic feet 
of free air at that pressure. This pressure is sufficient to keep in constant flow 
night and day three of the two thousand foot wells, 260 gallons of brine being 
discharged every minute from each. If the company desires they would be able 
to supply the entire demand by operating but two wells night and dav. 



664 



USE. 



The firm has also adopted a novel application of compressed air tools at the 
Salt Block. The salt is dumped in vast storage rooms below their grainers or 
vacuum pans, from i6 to 20 feet deep. When the salt is packed it has been found 
necessary before to use picks, grub hoes, etc., to quarry and break up the salt, so 
as to pack it into barrels. The vacuum pan salt being very fine grain and contain- 
ing a large percentage of brine becomes very hard and compact, so that it is .ver3f 
difficult to break it up for packing. During the past season laborers were scarce, 
and they could not get men to break up the salt ready for packing. In this emer- 




FIG. 253. — 130 VER PISTON AIR DRILL OPERATING AUGER FOR BORING IN SALT BLOCK. 



gency, the arrangement shown in the cut was brought into play. A truck was 
made with a horizontal shaft, to which was attached a ten-inch spiral auger, six 
feet long, and operated by the No. 2 Boyer Piston Air Drill, furnished by the 
Chicago Pneumatic Tool Company. The operator advanced the truck to the base 
of the salt wall, and the auger would penetrate a depth of 6 feet in 45 seconds. 
The holes were drilled as closely together as possible, and in from one to three 
hours, the section thus undermined would fall and break up all ready for packing, 
so that it was then only necessary to shovel it into barrels and head them up. 
By the use of this machine two and one-half days in a week, it was found that 



USE. 



665 



thirty packers would do the work which had previously required sixty packers, 
and the most laborious part of the work having been removed, no further difficulty 
was encountered in securing men to pack the salt. 



IMPROVED PNEUMATIC DISPLACEMENT PUMPS. 

The application of air pressure directly upon liquids contained in submerged 
receptacles of suitable design as a method of pumping, is old and well known 
to Pneumatic Engineers as the "Displacement System." 

While from a theoretical standpoint the efficiency of the "Displacement 
System" is low, its adaptability, by which existing economical sources of power 




FIG. 254. 



may be utilized for the production of the required air pressure, irrespective of the 
relative location of the source from which the water is taken, the low cost of 
installation when compared with an isolated pumping plant of the usual type, and 
the remarkable low cost of maintenance more than offsets the low efficiency 
and renders the system desirable and applicable to many cases. 

The displacement types of pneumatic pumps shown by the accompanying 
illustrations, embody recent improvements upon the construction formerly 
brought out by the writer, many of which, installed during the past five years, 
pumping water under favorable conditions, are giving entire satisfaction to the 
purchasers. 



666 



USE. 



These early patterns consisted of one or more iron chambers adapted to be 
submerged in the liquid pumped, having liquid ingress and egress openings closed 
by suitable valves, and an air valve for controlling the supply and release of air 
pressure to and from the submerged chamber. 

The air valve was placed in the chamber or directly on top, below the water 
level, or outside of the chamber above the water level. In all cases the movement 




i 



FIG. 255. 



of the air valve was controlled by floats, within the water chamber, arranged to 
actuate the air valve directly, or connected with supplemental valves which gov- 
erned the main valve. 

The mechanical difficulties encountered with these early constructions, and 
the objections thereto are chiefly as follows: 

First.— The limited available actuating power of all kinds of floats suitable 
to be contained within the water chamber, rendering the pump inoperative if the 
air valves become clogged or stick. 

Second.— The very great tendency of closed floats to collapse or fill with 
water under high pressure. With open end floats, the excessive loss of air 



USE. 



667 



required to displace the water which enters the mouth of the open end float, until 
the air entrapped therein corresponds to the external working pressure. 

Third. — ^The possible disarrangement of the floats, or air valve mechan- 
ism, from the rapid influx or efliux of water. The injurious elements — sand, 
mud or sediment, and the chemical action of the water which causes the air valves 
to leak and stick. 

Fourth. — The inaccessibility of the working parts, requiring the removal 
of the entire pump to make repairs of however slight a nature. 

The improvements embodied in the writer's new type of displacement 
pumps consist mainly, of the entire elimination of floats, the removal of all valve- 



^^ag|^^bg|A 



FIG. 256. 



actuating mechanism from the water chamber, and the placing of a self-contained 
air valve above the water level, thereby avoiding the difficulties mentioned. 

Figure 254, is a sectional view through the chamber of a single-acting type 
of the improved pump, showing the water admission and discharge valves, and the 
absence of all other moving parts below the water level. 

The automatic air valve which is the subject matter of U. S. Patent No. 
609,943, August 30th, 1898, consists of a main air valve controlled by an auxiliary 
valve, both of which are driven by differentiated pistons on which the air pres- 
sure is applied. By this means the valve motion is prevented from hanging up in 
a central position. 



668 



USE. 



The movement of the air valve is predetermined and adjusted to the maxi- 
ninm filling capacity of the water chamber, which is so proportioned as to exceed 
the discharge capacity, thereby insuring complete filling of water chambers. 

Pliable cup packings held out by brass tension rings are used on the piston 
valves to prevent air leaking. These cup packings, working in composition cylin- 
der linings, are subject only to the action of compressed air, from which sufficient 
lubrication is obtained by the oil taken up during compression of the air. 

In practice it has been found that these cup packings are exceedingly dur- 
able, wearing for several years and remaining pressure-tight. Being accessible 
they are easily and cheaply renewed if necessary. 

The automatic air valve may be placed just above the water level or anv 
distance away from the water chambers, as shown by the bored well displace 




FIG. 257. 



ment type (Fig. 255). It is preferable, however, to place the air valve near the 
water level to avoid the loss of air required to fill the connecting air pipes above. 
When the water chamber is nominally submerged the velocity of influx will 
carry the water in the air pipes some distance above the water level, and to a 
still greater height by an increased submergence. With the bored well displace- 
ment type (Fig. 255), there is usually sufficient submergence to reduce the clear- 
ance loss very materially. 

The water chambers are made in various forms and sizes to conform to 
the conditions of the sources or wells from which the water is taken. 

The single-acting types are adapted for moderate service up to 50 gal. per. 
minute capacity. 

For heavier service the duplex types (Fig. 256) are recommended. 

Figure 257 represents a "combination plant" pumping from one or more 
wells by modified types of the well known 'Tohle Air Lift," discharging therefrom 
into a receiver well at the surface, from thence by a "Duplex Displacement Pump" 
to any desired point of delivery above the surface. 



USE. 



669 



With this combination water may be effectively delivered at distant ele- 
vated points, by a single Air Compressing plant, from bored wells having a sub- 
mergence only sufficient for the economical operation of the "Air Lift" in dis- 
charging at the surface. 

These pumps are manufactured by the Merrill Pneumatic Pump Co., 141 
Broadway, New York. F. H. Merrill. 



PNEUMATIC DISPLACEMENT PUMP. 

We give below a full description of the Pitcher and Sargent (Somerville, 
Mass.), Pneumatic Water Raising Device as an example of direct displacement 
pneumatic pump. 

When water of a considerable depth is to be raised vertically upward, the 
"Air Lift" system furnishes a most practical means. It is, however, very often 

W^ Tf:jR Elevator 




FIG. 238. 



670 



USE. 



necessary to convey water, horizontally as well as vertically, to some height from 
shallow wells, springs and lakes by means of power generated at some distance 
from their sources of water supply. In such a case the Pneumatic Direct Dis- 
placement system is most practicable. 

In this system air is compressed at the most convenient place, and then 
conducted to a displacement tank submerged in the water to be raised. This tank 




FIG. 259. 

is provided with an air inlet and outlet and a water inlet and outlet. Compressed 
air is admitted to top of tank and displaces the water driving it out at bottom 
through a conducting discharge. The tank is again filled automatically with water 
and the operation is repeated. 

The difficulty giving rise to different kinds of displacement water raising 
devices is in the mechanism for automatically filling the tank with water. To 
accomplish this, it is necessary to shut off the supply and open the exhaust for air 



w 



USE. 671 



while the tank is filling with water, and to shut the exhaust and open the supply 
for air when the tank has filled. 

This device involves the displacement principle and overcoming the above 
difficulty by a simple but effectual means. The cylindrical tank T (Fig. 258) is 
fitted to slide vertically in standards M, which are mounted properly on metal 
base. The standards bear two weighted levers W, which engage with lugs L on 
tank, V is an eighth turn three way valve which controls the compressed air 
supply and exhaust. The operation is as follows: compressed air enters at S, 
passes through flexible pipe F to top of tank, driving water out through flexible 
pipe D to reservoir. When the tank is full of air, its buoyancy overcomes the 
weight of levers W, it rises to dotted position, shifting the valve so that air sup- 
ply is shut off, and air in tank escapes through F, to free air at E. The weighted 
levers now hold tank up until it has filled with water through I. When full of 
water the weight of tank causes it to drop to original position and process is 
repeated. 

To work properly, the tank when submerged and full of water should 
weigh one-half force due to its buoyancy when full of air. The efficiency of a dis- 
placement pump is 100 p. c, when the volume of water raised is equal to the 
volume of air (at effectual pressure) allowed to escape. By adjusting the 
weights W on the levers in this device, you are able to so balance the tank that 
it will not fall until it has entirely filled with water, thus avoiding any clearance 
space in top of tank to be filled with air before the water can be forced out. In 
fact, the tank fills so quickly that the water rushes up the pipe F and out the 
exhaust E (provided the valve is near the surface of water) before the inertia 
of the tank and weights is overcome and the tank falls. Under this condition, 
and disregarding leakage, loss of power is minimum. 

Fig. 259 shows also the air compressor used with windmills, the plunger 
working from under side and attached directly to pumping rod of mill by side rods 
and cross heads. 



DRIVING PUMPS BY COMPRESSED AIR. 



BY WILLIAM cox. 

"Compressed air may be, and should be, much more extensively used than 
it has been hitherto for operating pumps." 

It must not be supposed, however, that any common steam pump, having 
attached to it a pipe supplying air under any hap-hazard pressure will perform 
satisfactory service. To insure such various details relating to the manifold 
operations to be performed must be carefully considered and duly taken into ac- 
count, so that from the variety of conditions presented, a harmonious whole may 
be evolved. And even then, when the installation, if it may be dignified by such 
a term, has been made with judgment and due regard to the exigencies of the 
case, high economy must not be looked for or expected, as the common direct- 
acting pump, no matter how driven, is and will ever be a waste producer. Taking 
the pumps, however, as they are generally met with, the object of this paper is to 



672 USE. 

present in as simple a manner as possible the conditions which must be fulfilled, 
so that with the material at hand, or easily secured, the best results may be ob- 
tained. 

In what follows the following nomenclature is observed throughout : 

Ds or Da=Dianieter of steam or air cylinder in inches, 
d=Diameter of water cylinder in inches, 
l='Lenglh of stroke in inches, 
n— Number of single strokes per minute, 
ps— Piston speed in feet per minute, 
1 X n 



12 

E=^Useful effect, efficiency or corrected capacity, 

G^Gallons of water required to be discharged per minute, (U. S. 

Gallons of 231 cub. ins.), 
P=Gauge Pressure of the air in pounds per sq. in., 
V=Equivalent volume of free air required, 
li=Head in feet to which the water is to be pumped, 
p=Resistance per square inch on the pump piston = 0.433 h. 

The first point which presents itself for our consideration is the quantity 
of water that is required to be handled, with the corresponding necessary diameter 
of (he water cylinder of the pump, so as to secure good results in this part of the 
system. The formula giving the theoretic discharge of any pump cylinder is : 

O = °\7*'^^'5'**^* X 1 X n 
' ~ ^^ 23I 
= o'oo34d" X 1 X n 
= oo4o8d'^ xps (1) 

By transposition wc have 

d~ = — - — — -- whence 
o"04o8p8 

''=^Nr- (^) 

and allowing for a piston speed of 100 feet per minute, which is very commonly 
assumed as reasonable, we have: 

fl=o-495 /gT (3) 

The following table, calculated from Eq. (i), gives the theoretical dis- 
charge of water cylinders of various diameters, in gallons per minute, the pistoi^ 
speed being assumed throughout as being 100 feet per minute ; 



USE. 

TABLE 59. 



673 



Diameter of 
Water Cylinder. 


Discharge. 


Diamete of 
Water Cylinder. 


Discharge. 


3 inches. 


16-32 c. ft. 


914 inches. 


368 22 c. ft. 


2H " 


25-50 " 


10 '• 


408 00 •• 


3 


36-72 " 


11 


493-68 " 


3K " 


49-98 '* 


12 


587-52 " 


4 


65-28 " 


13 


689-52 " 


4K " 


82-62 " 


14 


799-68 " 


5 " 


102 00 " 


15 


918-00 " 


5^ " 


12342 " 


16 


1,044-48 " 


6 


146-88 " 


17 


1,179-12 '« 


6K " 


172-38 " 


18 


1,32192 " 


7 


199-92 " 


19 


1,472-88 '• 


7K " 


229-50 " 


20 


1,632-00 " 


8 


261-12 " 


21 


1,799-28 " 


«^ " 


294-78 " 


22 


1.974-72 " 


9 


330-48 " 


24 


2,35008 " 



I 



By means of this table the size of the water cylinder required to discharge a 
given quantity of water, on a basis of a piston speed of 100 feet per minute, is at 
once approximately seen. Thus, to deliver 100 gallons a minute, a 5-inch cylin- 
der would be evidently required. 

It is well, however, to note that for pumps having but a short stroke, 100 
feet piston speed per minute is excessive, as it causes too frequent reversal of the 
valves, while for long-stroke pumps this speed may be somewhat increased. 

The above discharges are the theoretical ones, which are far from being at- 
tained in practice. It would be safer and more correct, therefore, to assume as a 
general rule that the capacity of the water cyli^iders should be increased by at 
least 20 per cent., to cover losses arising from looseness of the piston valves, etc. 
The simplest way of doing this is to add 20 per cent, to the required discharge, 
and then find in the table the size of the water cylinder for this increased dis- 
charge. Thus, in the above case, 100 gallons X 1.20= 120 gallons, for which by 
ilie table a s^/^-inch cylinder would be necessary. If it should be preferred to 
work this out directly by formula we have : 

20G 



d» = 



o o4o8ps 

\P8 



, whence 



(4) 



and for 100 feet piston speed 



d=o-54i/G. 



.(5) 



Having thus calculated the diameter of the water cylinder which will at the 
Kiven piston speed deliver the required quantity of water, we must next determine 
I he diameter of the air cylinder, and the working pressure of the air which will 
raise the required quantity of water to the desired height. 

The first thing to be done here is to decide upon a suitable pressure of the 
air. For several reasons high pressures are not recommended, the chief pne being 



674 USE. 

that of economy, seeing that, although a lower pressure will require a greater vol- 
ume of free air, yet the proportionate and absolute cost of the power necessary to 
operate a larger sized air cylinder (which consumes the greater volume of free air 
at the lower pressure) is considerably less. 

The steam or air pressure required to raise water to any given height is 
found by the formula. 

p_ pxd^ 



o'433h xd- 



.(6) 



transposing which, on the assumption that the pressure P has been previously de- 
cided upon, we have for the size of the air cylinder : 

P^,^o-433hxd^ ^^^ 

As in the water cylinder considerable losses occur, so in the air cylinder 
such are inevitably met with, owing to clearance, leakage, etc. Assuming these to 
be IS per cent, of the piston displacement, formula (7) becomes: 

j^^., ^ o-433hxd^xi-i5 
looP 
- O'Shxd^ ^g^ 

Taking the case already referred to, where it is required to deliver 100 gal- 
lons of water per minute, using a 5^'2-inch water cylinder, and assuming that the 
height to which it is to be raised is 80 feet, and that an air pressure of 20 pounds 
be used, we have by Eq. (8) : 

p^o_ o 5x80x5-5x5.5 
20 
= 60-5 
and Da=7"8 inches. 
It would, therefore, be reasonable, as well as safe, in such a case to select a 
pump having say 8 x 6-inch cylinders and 12-inch stroke. 

The next and last point, which is one of considerable interest, is the volume 
of equivalent free air required to do the work thus determined. For this purpose 
we have the formula: 

y_ o7854Da^xlxn ^^^, 
1728 ^ 
=o-oo545Da^ X ps X Wg (9) 

in which the first expression gives the required volume of compressed air, while 
the second one, W2, reduces this volume to its equivalent volume of free air, being 
a simpler form of expression for : 

147 ^ 

By this formula the value of W2 for 20 pounds pressure is : 
I + (0.068 X 20) = 2.36 



USE. ' 675 

and inserting this value in Eq. (9) we have for the example given : 

= 77.8 cubic feet. 
V = 0.00545 X 60.5 X 100 X 2.36 
Assuming, as before, a piston speed of 100 feet per minute and adding 15 
per cent, to the volume of free air required, to compensate for frictional and other 
resistances, we have : 

V=o-63 X Da^ X W3 (10) 

which gives 90 cubic feet of free air required to pump 100 gallons of water per 
minute to a height of 80 feet, the pressure of the air being 20 pounds per square 
inch, the diameter of the water cylinder 5^/^ -inches, the diameter of the air cylin- 
der 7.8 inches, and the piston speed 100 feet per minute. 

It must, of course, be understood that these formulas do not cover undue 
losses occasioned by friction in the delivery pipes, when these are either of too 
small diameter or considerable length. This point is an important one and re- 
quires equally careful consideration, so as to reduce this friction to a minimum. 
Space does not allow of this problem being gone into here, as to do it justice 
would require an article^to itself. 

From what precedes, it will be seen that the formulas required for solving 
problems relating to pumps driven by compressed air, are : 

For the diameter of the water cylinder Eq. (5). 

For the diameter of the air cylinder Eq. (8). 

For the volume of free air Eq. (10). 

It is frequently desired to know in a simple manner how many cubic feet 
of free air at a certain pressure would be necessary to pump a given quantity of 
water to a required given height, without, for the time being, considering the 
sizes of the air and water cylinders or the piston speed. That this can be done, 
although not generally so supposed, and that by a very simple formula, will now 
be explained. 

First : — Theoretically. 

Eq. (i) gives 

G=o-o4o8d2 X ps 



whence 

o*o4o8ps 



d=^ = — ^ 'lO 



Eq. (7) stands 

o-433hxd^ (7) 

Inserting the value of d^ as given in Eq. (11) in Eq. (7) we have 

w=°-:^. G (,3) 

P o'o4o8ps 
Again, we have by Eq. (9) 

T=o-oo545Da^ X ps x Wg (9) 

From equations (12) and (9) we obtain 

043311 xG 
'P X o"04o8ps 
and by cancelling and reducing 

V-o-o5784^-^xW, (13) 



V^o-oo545;^^^^"V xPsxW, 



676 USE. " ' 

the only quantities requiring to be known being 

h=the head in feet to which the water is to be pumped, 
G=the number of gallons of water to be pumped, and 
P=the pressure of the air to be used. 

Second: — With the various losses taken into account, as explained in the 
last article, 

Eq. (11) with 20 per cent, added gives 

0*0408x100 ps 

= t> (,4) 

0-034PS 
Eq. (7) with 15 per cent, added gives us 

Da^=^^^^^'sameas (8) 

Combining equations (14) and (8) we have 

°»-°-?%-^ -■■-■ ■ ^-' 

Again, equation (9) with 15 per cent, added gives us 

V=o'oo63Da^ X ps X Wg (16) 

and by combining equations (15) and (16) we obtain 



and by canceling and reducing 



^ o*5hxG _,- 

V=o-oo63-— ^^ X ps X Wj 

Pxo"034ps 



h X G ,^^ , . 

V = o-093-^ X Wg. (17) 



in which, as before, the only quantities required to be known are 

h=the head in feet to which the water is to be pumped, 

G==the number of gallons of water to be pumped, and 

P=the pressure of the air to be used. 
Let us now take the example given in detail in the last article, and see 
how nearly the results agree. We have given 

h=8o feet, 

G=ioo gallons, 

P=20 pounds, and 

W2 for P=20 pounds^ 2.36, 
we have therefore by Eq. (17) 

Q -Sox 100 

V— o"o X 2";6 

20 -^ 

=87 8 cubic feet of free air 

as against 90 cubic feet found previously. The slight difference is, however, ex- 
plained and fully covered by two or three items being taken in the former paper 
approximately, such for instance as the diameter of the water cylinder, which is 
5.4 inches by the formula, and not 5.5 inches, which was taken from the table, 
which allows a slight over-volume of delivery (3.42 gallons), 



USE. 677 

The solution of the problem by this direct method therefore fully agrees 
with the step-by-step one, and for a preliminary study of any case which may 
arise, is very much simpler. 

If it be found that such a quantity of free air is available, other details re- 
quired for making the installation a success, can now be obtained by means of 
equations (14) and (8), which give in a very simple manner the diameters of the 
water and air cylinders, based upon any suitable piston speed. 

Thus, by Eq. (14) and assuming a piston speed of 100 feet per minute, 
we have 

o-o34ps 

IPC 

~o"034 X 100 

=29-41, and 

d=5 4 inches. 



Then by Eq. (8) we have 



j^^,^o-5hxd^ 



P 

=ro*5 x8ox 29*41 

20 
=:58-82, and 
Da=7'67 inches. 

It is the writer's opinion that equation (17) will be found exceedingly use- 
ful by mining and other engineers who may have to figure upon the use of com- 
pressed air for driving common pumps. 

Another question which will also be of interest, although it may some- 
times be overlooked, is the question of power cost. As previously stated, high 
powers are not, when examined from this standpoint, recommended. 

The horse-power required by the air cylinder of a compressor is 

^ p^o7854d-xMpxps 

33000 

and the volume of free air compressed by the same is 

o7854d=^ X Ps 



(19) 



144 

The horse-power required therefore by the air cylinder to compress one 
cubic foot of free air is found by dividing Eq. (18) by Eq. (19) which gives 

p_ 0785 4 dg X Mp X Ps X 144 
~ o'7854d=^ xpsx 33000 

=-— (20) 

229 ^ ' 

The following table gives the mean effective resistance, or mean pressure 
Mp to be overcome by the air cylinder piston to produce various terminal pres- 
sures,* and the horse-power required by the air cylinder to compress one cubic 
foot of free air to the same terminal pressures, calculated from Eq. (20). 



* From C0MPRB88BD Air, by Frank RichardSy A. 8. M. E, 



678 



USE. 

TABLE 60. 



Terminal Pressure 
P 


Mean Pressure 


Horse-power per 
cubic foot of 






free air. 


20 pounds, 


144 


pounds, 


0.0628 


25 " 


17.01 




0.0743 


30 " 


19.4 




0.0847 


35 " 


21.6 


" 


0.0943 


40 " 


23.66 




1033 


45 " 


25.59 




0.1117 


50 " 


27.39 




0.1196 



Referring again to Eq. (17) we may transpose it and obtain 

P 



and if we substitute for 



hxG 
P 



V 



W. 



0*093 
the term X, we have 



o'G93W. 

h X G=V X X (21) 

The following table gives the values of W2 and 0.093 W2 for different pres- 
sures, with the corresponding values of X. 

TABLE 61. 



Pressure 






P 




Wo 


0-093 W 2 


X — 


P 






" 0.093W2 


5 pounds, 


1.34 


0.12462 


40.122 


10 ' 




1.68 


0.15624 


64.004 


15 




2.02 


0.18786 


79.846 


20 




2.36 


0.21948 


91.124 


25 




2.70 


0.25110 


99.562 


30 




3.04 


0.28272 


106.324 


35 




3.38 


0.31434 


ni.344 


40 




3.72 


0.34596 


115.620 


45 




4.06 


0.37758 


119.180 


50 




4.40 


0.40920 


122.190 



This table enables us to obtain in a very simple manner the volume of free 
air required to pump any given quantity of water to any desired height. Thus, 
to continue the example already referred to, 

h X G=8o X 100=8,000, 
and dividing by X or 91 (omitting decimals) we have for 20 pounds pressure 

^ _ 8000 

9^ 

which is practically identical with the solution already found by means of Eq. 
(17). 

If we now combine Tables 60 and 61, we obtain the following one, which 
will be often found useful: 



cubic feet of free air. 



USE. 

TABLE 62. 



679 



V X X 


P 


V 


H. P. 


= h X G 








9112 


20 pounds, 


100 cub. ft. 


6.28 


9956 


25 " 




7.43 


10633 


30 




8.47 


11134 


35 




9.43 


11562 


40 




10.33 


11918 


45 




11.17 


12219 


50 




11.96 



Taking the previous example, we have, therefore, for the horse-power re- 
quired by the air cylinder 

6-28x88 

= 5 '53 horse power. 

100 -' ^ ^ 

It has been stated that high pressures are not economical. Let us, there- 
fore, work out the foregoing example with an assumed pressure of 40 pounds, 
so as to be able to judge of the altered conditions. 

We have, therefore, in the first place, from Table 61 
h X G 80 X 100 
X "^ 115-6 
=69 cubic feet of free air. 
Now, by Table 62 we have 

10-33x69 . 

-= 7*13 horse-power. 

100 '^ 

We see, therefore, that although there is an economy of 88-69=18 cubic 
feet of free air to be compressed, yet the power-cost of doing the work is 7.13- 
5.53=1.6 horse-power greater. Other cases, if similarly worked out, would 
demonstrate the same fact. 
Formula (21) which is 

h X G=V X X 
shows 

I St. — For a given pressure, the volume of free air required varies directly 

as h X G. 
2d. — If the product of head into quantity of water is the same in different 
cases, the pressure will vary inversely as the volume of free air re- 
quired ; or the volume of free air required will vary inversely as the 
pressure employed. 

3d. 



h X C 
-For equal values of — :^j—, the pressure necessary will be the same. 



I 



V 

Thus, if V = 100, h = 100 and G= 100, then X = 100, which is equiva- 
lent to a pressure of 25 pounds, as per Table 61. 

• So also, if V = 100, h = so and G = 200, X = also 100, and consequently 
as per same table, the pressure required will likewise be 25 pounds. 

I trust that it has been clearly shown that the volume of free air required 
and the power-cost can be ascertained without any reference to the sizes of the air 



6So tJSE. 

and water cylinders, and that these are questions of detail to be afterwards con- 
sidered in accordance with the formulas given, when working out plans for an 
installation. 

Of course, the losses I have taken may vary from those stated, as much 
depends upon the pumps employed and the care used throughout in making the 
installation. The same method of treatment must, however, be followed in all 
cases. 

In connection with what I have already written, it may be desirable some- 
times to ascertain in a ready manner the ratio which should exist between the air 
and water cylinders so that the best results may be obtained. Equation (8) sup- 
plies this information in the simplest form. It is 

■n 2 _ o'shxds 
Da p — 

from which we obtain by transposition 

Da^ : d2=o-5h : P (22) 

or, to express it so that it may be easily memorized, 

Area of air cylinder is to area of water cylinder as half the head is 
to the pressure. 
or again, we have 

Da : d= /"^ : i/¥" (23) 

that is, 

Diameter of the air cylinder is to the diameter of the water cylinder, 
as square root of half the head is to square root of the pressure. 
Taking the example already given, where h=8o feet, and P=20 pounds 
we have 

Da^ : d2=4o : 20 
= 2:1 
or 

Da:d=i/'2 : i/l 

=1-414: 1 

It will be clear from what has been written in the first article that the 
FIRST point in every case to be carefully ascertained is the diameter of the water 
cylinder and the piston-speed, after zvhich the required diameter of the air 
cylinder can be easily found by means of the above ratio-formula. 

The diameter of the water cylinder depends upon the quantity of water to 
be pumped per minute and the piston-speed; or, in other words, the volumetric 
capacity of the water cylinder per minute is the sectional area of the cylinder 
multiplied by the length of stroke in inches, and the number of single strokes per 
minute. This product, which is the capacity in cubic inches, divided by 231, 
gives the capacity in U. S. gallons per minute. Reduced to its simplest form, 
this becomes as in Eq. (4) 



d=5-4^- 



ps 

In the above example we assumed G=ioo and ps=ioo feet per minute, so we have 



J I 100 

=5'4 inches 



ttSE. 



68i 



Given then, d=5.4 inches, clearly 



Da=- 



V 2 



or Da 



:5-4x 1-414 
:7"64 inches, 



which agrees with the result already obtained, if in place of Da=S.5 as pre- 
viously given, we take Da.=5.4 inches as above. It should be remembered that 
the diameter 5.5 inches was taken from Table 59, and is correct for 102 gallons, but 
a little too much for 100 gallons. Of course, cylinders are not made to decimal 
sizes, such as 5.4 inches, but to fractional diameters as 5^ inches. 

The following table gives the ratio of the diameter of the air cylinder to 
the diameter of the water cylinder for different heights to which the water is 
to be pumped, and for different air-pressures, the diameter of the water cylinder 
being taken throughout as i inch : 

TABLE 63. 
Ratios of diameter of air cylinder to diameter of water cylinder. 









PRESSURES 








Height, 
















Feet. 


















20 lbs. 


35 lbs. 


30 lbs. 


35 lbs. 


40 lbs. 


45 lbs. 


50 lbs. 


fiO 


1.12 


1.00 


0.91 


0.84 


0.79 


0.74 


0.71 


100 


1.58 


1.41 


1.29 


1.20 


1.12 


1.05 


1.00 


125 


1.77 


1.58 


1.45 


1.34 


1.25 


1.18 


1.12 


150 


1.94 


1.73 


1.58 


1.45 


1.37 


1.29 


1.22 


175 


2.09 


1.87 


1.70 


1.58 


1.48 


1.39 


1.32 


200 


2.24 


2.00 


1.82 


1.69 


1.58 


1.49 


1.41 


225 


2.37 


2.12 


1.94 


1.79 


1.68 


1.58 


1.50 


250 


2.50 


2.24 


2.05 


1.90 


1.77 


1.67 


1.58 


275 


2.62 


2.35 


2.14 


1.98 


1.85 


1.75 


1.66 


300 


2.74 


2.45 


2.24 


2.07 


1 94 


1.82 


1.73 


325 


2.85 


2.55 


2.33 


2.16 


2.02 


1.90 


1.80 


350 


2.96 


2.64 


2.42 


2.24 


2.09 


1.97 


1.87 


375 


3.06 


2.74 


2.50 


2.31 


2.16 


2.04 


1.94 


400 


3.16 


2.83 


2.58 


2.39 


2.23 


2.11 


2.00 


425 


3.26 


2.92 


2.66 


2.46 


2.30 


2.17 


2.06 


450 


3.35 


3.00 


2.74 


2.53 


2.37 


2.24 


2.12 


475 


3.44 


3.08 


2.82 


2.60 


2.44 


2.30 


2.18 


500 


8.53 


3.16 


2.89 


2.67 


2.50 


2.36 


2.24 



Ratios for intermediate heights and pressures may be obtained by interpolation. 

Example. 200 gallons of water to be pumped to a height of 125 feet, the air- 
pressure being 25 pounds. Piston-speed 100 feet per minute. 
We have in the first place 



Diameter water cylinder=5 4^/— 

\ 10 

=5'4x 1/ 2=764 inches, 



200 
100 



682 USE. 

Now, by Table 63, we find under 25 pounds pressure, in line with 125 feet 
height, the ratio 1.58 to i, so that the diameter of the air cylinder should be 
7.64 X 1.58=12.1 inches. 

In practice these two sizes will of course not be met with, so to secure the 
pumping of the required quantity of water we may safely select a pump with an 
8-inch water cylinder. Then, according to the ratio of 1.58 to i.o, we should 
have an air cylinder of 8 X 1.58=12.64 inches diameter. If a 13-inch cylinder 
could be had, it would about fill the requirements; but as such a combination is 
hardly likely to be met with, we should probably have to take a 12 inch, and try 
to force the air-pressure up to 28 pounds, which is about the interpolated value 
by the table for a ratio of 1.50 to i.o, or 12 to 8 inches. 

By following as near as can be the ratios set forth in Table 63, and slightly 
adjusting piston- speed and air-pressure so as to counterbalance any slight varia- 
tion of diameters of the cylinders, water may be pumped in any quantity to any 
height, with the least volume of free-air possible, in accordance with Eq. (17). 
Common pumps may then do their work economically (relatively), and com- 
pressed air will be looked upon as a valuable and not a wasteful agent. To re- 
peat an old saying, Use, but do not abuse. Of course, if the pumps are of the 
best, and in good condition, the various losses may be slightly reduced, and 
somewhat more favorable results may be obtained. 

Example. It is required to raise 200 gallons of water per minute to a height of 
125 feet, the maximum air-pressure being 30 pounds. 

The quantity of water being considerable, and requiring necessarily a fair 
sized cylinder, let us assume a piston-speed of 120 feet per minute. 

We have in the first place by Eq. (4) 

V ps 

=5'4a/ =6'97 inches, 

\ 120 

Now, by Table 63, we see that for 30 pounds pressure and a height of 125 

feet, the ratio of the cylinders is 1.45 to 1.0, which gives for the air cylinder 10. i 

inches, or say 10 inches for the air cylinder and 7 inches for the water cylinder. 

We then have for the volume of free-air required, by Eq. (10) 

V=o-oo63Da^ X Ps X Wo 

=0-0063 X 100 X 120 X 3-04 

= 229 "8 cubic feet. 

To verify this result, and to see how near it approaches the ideal, we have 

by Eq. (17) 

^j h X G ^,, 

V=o-o93-p- X Wo 

125 X 200 
=0*093 — — — X3-04 

= 235 cubic feet. 
Allowing for the decimals in the different equations, we see that the re- 
sults obtained by the two methods substantially agree. We may, therefore, say 
that for the case under consideration a better combination could scarcely be had 
than that found as above, namely 10 by 7 inch cylinders, 30 pounds air-pressure, 
and 120 feet piston-speed. 



USE. 



683 



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■^stwy^A*^ 



NORWICH SEWERAGE WORKS. 

Owing to its configuration and geological conditions it has been a mattei 
of some difficulty to provide Norwich with an efficient system of sewerage, and 
some of the most eminent engineers of our time have been consulted and engaged 
in trying to drain the city effectually. Up to the year 1865 the city was drained 
by over 300 different sewers, all of which delivered their contents into the river 
Wensum, with the result that it was polluted to an alarming extent. At this 
period the late Sir Joseph Bazalgette was called in to prepare a scheme for the 
drainage of the city. He proposed a deep main sewer on the southern side of the 
river, into which all the tributary sewers from both sides of the river were to dis- 
charge by gravitation to the outlet at Trowse, where the main pumping engines, 
which were to be capable of lifting 2^ million gallons of sewage per day to the 
sewage farm at Wittingham, were to be erected. These works were carried out 
in 1871. 



USE. 



685 



The difficulties in constructing the main deep outfall sewer were, however, 
very great, and when completed it was found to be so leaky that the quantity of 
water pumped at the Trowse pumping station was 5,000,000 gallons per day, or 
just twice the ultimate quantity provided for by Sir Joseph Bazalgette. The cost 
of pumping thus became very heavy, the coal consumption being about eight tons 
per day. 

All the attempts made to render the leaky sewer water-tight by lining it 
with cast iron tubing, &c., proved futile, and in 1887 the Corporation, on the ad- 
vice of Mr. P. P. Marshall, the then city engineer, decided on: — (i) The con- 
struction of a new main outfall sewer at a higher level than the old one, and the 
abandonment of the old one. (2) The adoption of the Shone system for raising 



'miemm^<9^ 




Li.EV'/RTiOH 
FIG. 260. 

the sewage of the low-level districts into the new main outfall sewer. (3) The re- 
drainage of the whole of the city on the separate system. The air required for 
working the ejectors is compressed by means of the water power which is avail- 
able in the river Wensum at the New Mills, where formerly two under-shot 
water wheels were worked, but which only gave about five horse power each 
The water-power now works two Victor turbines, which give 40 to 50 brake 
liorse-power each, one of which is sufficient to compress all the air for operating 
the various ejectors required to drain the low-lying parts of the city. The New 
Mills belong to the town, and as flour mills they were let to tenants for a mere 
nominal rent. By thus utilizing the Wensum river water, the working cost of the 
motive power for raising the sewage from the low-lying area becomes practically 
inappreciable. The ejectors at all the stations are in duplicate, and are placed in 
chambers of cast iron tubing, sunk below the level of the street surfaces. These 



686 



USE. 



chambers or stations were sunk in the same manner as cast iron cylinders used 
for bridge foundations are sunk. The bottom parts of the castings are provided 
with a strong cutting edge, to facilitate the work of sinking them. The soil was 
excavated from the inside of the pits sunk to contain them, and wherever neces- 
sary it was removed under air pressure, the entrance tube to the chamber being 
provided with an air lock. Heavy pumping, which might have proved destructive 
to adjoining properties, was thus avoided, and no difficulty was found in sinking 
the chambers in the water-logged subsoil to their proper depth. 

The ejector stations Nos. 2, 3 and 3A discharge into one of the inverted 
syphons which starts in Duke of York street, just above Bishop's Bridge, goes 







^/•v. .: :«.-_^. 



m 



FIG. 261. 



along Riverside avenue, under Foundry Bridge, along Prince of Wales street, 
Rosslane and Mountergate street, and finally debouches into the main outfall 
sewer in King street. All the sewage from the Thorpe district is discharged into 
this syphon through the sewers in Bishop's road. Gas Hill, Rosary road and 
Thorpe road. These four roads rise steeply from Duke of York street and River- 
side avenue, and four cast iron branches from the syphon pipes are carried up the 
roads to a manhole situated above the hydraulic gradient of the syphon pipe. The 
population of the gravitation area discharging into this syphon is 4780, and of the 
ejector area 5735 inhabitants. Ejector station No. 4 discharges into a second 
syphon, which conveys the sewage from the northern part of the city, viz., the 



USE. 



687 



Noncehold and Catton Wards, through three branches from St. Augustine street, 
Magdalen street and Bull Close street, meeting at Stump Cross in a 21-in. pipe, 
which is increased to 24-in. at the ejector station. This syphon pipe is flushed at 
frequent intervals from a flush tank of 3000 gallons capacity in Magdalen street, 
which receives the sewage from part of the Catton Ward, and discharges it 
through one of Shone and Ault's full-bore flushing syphons every time the 
tank is full, thus sending a powerful current through the syphon pipe day and 
night. 

The population of the gravitation area draining to this syphon pipe is 
25,180; that of the ejector district 12,026 inhabitants. The syphon pipe passes 
from Magdalen street, through Fye Bridge street, under the Fye Bridge, along 




PLAN 



FIG. 262. 



Wensum street and Tombland to the main outfall sewer in Prince's street. 
Ejector station No. 5 discharges direct into the outfall sewer in Benedict street, 
through an i8-in. main passing along Lower Westwick street and St. Margaret 
street. The total population of the area drained by the ejectors is thus 39,911 
inhabitants, and an additional area with a population of 29,960 inhabitants is 
drained through the inverted syphon pipes. The whole of the sewage goes, as 
already stated, through the new outfall sewer to the Trowse pumping station, 
where it is lifted to the sewage farm by means of large beam pumping engines. 

To ascertain the available water power at the New Mills, the water in the 
river Wensum was measured on May 9th, 1893, after a long period of dry 
weather. The mean sectional area of the river just above the Mills was found to 
be -So per cent, of this, and the velocity o -05256 ft. per second. The quantity of 



688 



USE. 



water per minute was therefore 57,700 gallons. The fall at the Mills is 6 ft. 6 in., 
and the total power of the water is therefore 113 :6 horse power. The old wheels 
barely gave out 10 per cent, of this power, and the engineers therefore proposed 
to have them removed, and to put down a pair of 48-in. Victor turbines. These 
turbines have been used extensively in the United States and Canada, and they 
have recently been used for a large electric installation at Worcester, where they 
have given excellent results. 

The Victor turbine is very simple in construction, strong and easily regu- 
lated. It gives nearly as high an efficiency with a greatly reduced gate opening 
as when working full power, and all the various parts are made to standard 
gauges, so as to be interchangeable and easily replaced. 

Each turbine drives a set of horizontal air-compressing engines, each set 
having two air cylinders 15-in. diameter, i8-in. stroke, and able to compress 650 




FIG. 263. 

cubic feet of free air per minute to a pressure of 18 lb. per square inch, when the 
turbine is using 30,000 gallons of water per minute. 

During heavy floods in the river, the total water below the mill rises to the 
level of the ordinary head water above, and then all the sluices must be opened to 
avoid the flooding of the upper parts of the town and the western suburbs. On 
such occasions there is no available water head for working the turbines. Pro- 
vision has therefore been made for driving the air compressors by steam by 
attaching compound steam cylinders to the tail rods of the air-compressing 
cylinders. The steam cylinders are 93^ in. and 145^ in. diameter, and arranged 
in such a manner that they can be readily connected up when a flood occurs. 
Steam is supplied to work the compressors from a Babcock and Wilcox boiler, 
heated with town refuse burnt in two furnaces constructed by the Horsfall Refuse 
Furnace Syndicate. These works adjoin the air-compressing station, and form 
part of the New Mills property. Before the Victor turbiqe was substituted for 



p^ 



USE. 



689 



the old water wheel, nine sluices were provided, the largest being 6 ft. by 4 ft. 6 
in. deep, with a combined area of 182.5 square feet. They were, however, very 
difficult to open, and when heavy floods occurred some of the smaller openings 
became choked by debris. Sir John Hawkshaw recommended, in 1879, that they 
should be enlarged, and in the new works connected with the Victor turbines 
care was taken to provide large sluices of modern design. The waste water 
sluice is of the well-known Stoney type, 14 ft. 3 in. wide, 8 ft. deep, and in addi- 
tion to this two sluices have been provided behind each of the turbines, 12 ft. 6 in. 



NORWICH 



REFERcNCE. 
Cjtctor Statioifs. 
Sypfiort Pipes. 




>PUMPlMa STATION 



FIG. 264. 



wide by 5 ft. high, giving a total sluice area of 239 square feet, without reckoning 
the port area of the turbines themselves. 

As the new buildings fronting the direction of the flow of the river are 
narrower in their width than the old buildings, there remains ample room for 
further extension of the sluices hereafter, if those now provided should prove to 
be inadequate during periods of heavy floods. 

The compressed air is conveyed from the compressors in the air-compress- 
ing station to Lower Westwick street through a 9-in. cast iron socket pipe, and 
from that point the air pipes are gradually reduced in size to correspond to the 
volumes of air to be conveyed by them to the various ejector stations. 

Two air receivers, 7 ft. diameter, 20 ft. high, are provided in the engine- 
house, and all the compressed air passes through these, being thereby cooled and 



690 



USE. 



dried before it enters the air mains. It is estimated that the cost of the whole 
scheme will be £164,000, and the works are being carried out by Mr. A. E. Collins, 
the city engineer, Messrs. Shone and Ault, of Westminster, being the consulting 
engineers for the Shone ejectors and machinery in connection therewith. The 
contractors for the Shone ejectors, air-compressing machinery and turbines, air 
and sealed sewage mains, were Messrs. Hughes and Lancaster, of Westminster 
and Ruabon. Contracts for the sewers in the various districts have been placed 
with Messrs. Monk and Newell, of Liverpool, and Messrs. B. Cooke & Co., of 
London. 

TABLE 66. 

Tabular Statement Showing Detailed Particulars Relating to Ejector Stations, 

Norwich Sewerage. 



Ejector Station. 



a. Populationof district, present 

b. Population of district, future 

c. Number and size of ejec- J 

tors ( 

d. Quautitj-^ofsewagedischarged 

per minute, present 

e. Quantityofsewagedischarged 

per minute, future 

f. Ground level at ejector sta- 

tions 

g. Invert of lowest sewer at sta- 

tion manhole 

h. Delivery levels of sewage 

mains (centre of pipe) 

i. Total dead lift 

k Total pipe friction in feet . . . 

1. Total dynamic head 

m. A ir pressure required 



No. 2. 


No. 3. 


No. 3a. 


No. 4. 


No. 
Westwick 


No. 7. 
Carrow 


Foundry 


Bishops 


Barrack 


Fye 


Street, 


Bridge, 


Bridge. 


Bridge. 


Street 


Bridge. 


near New 
Mills. 


Colemans' 
Works. 


2910 


1425 


1400 


12,026 


18,150 


4000 


4110 


2165 


2160 


12,026 


23,550 


8000 


Two of 


Two of 


Two of 


Two of 


Two of 


Two of 


250 gals. 


150 gals. 


150 gals. 


500 gals. 


1000 gals. 


300 gals. 


196 gals. 


89 gals. 


88 gals. 


780 gals. 


1184 gals. 


250 gale. 


271 gals. 


136 gals. 


135 gals. 


780 gals. 


1521 gals. 


500 gals. 


900 


10-19 


9-00 


10-00 


12-40 


14-7 


-5-50 


-2-60 


-4-00 


-4-25 


^-86 


-12-16 


4 5-75 


+5-75 


- 5-75 


48-00 


-f 10-92 


- 0-91 


1577 


11-27 


12-67 


18-00 


21-53 


18-26 


2-91 


11-26 


17-54 


1-38 


1-97 


0-93 


18 68 


22-53 


3019 


19-38 


23-50 


1919 


9-00 


10-00 


14-00 


900 


11-00 


9-00 



Total. 



39,911 
52,011 



2587 gals. 
3343 gals. 



The particulars of the various ejector stations, with the population of thv 
ejector districts, are shown in the table above. 

Our illustrations, taken with the preceding article, are self-explanatory.— 
The Engineer. 



PNEUMATIC CESSPOOL EXCAVATOR. 
A pneumatic apparatus for emptying cesspools has been invented by Eng- 
lish manufacturers and is now in use at Pokesdown, England. It consists of a 
tank for sewage and a dome and connecting pipe for producing a vacuum in the 
tank. The tank is mounted upon an ordinary four-wheel truck and can be drawn 
"by a horse. A smaller portable truck supports a vacuum pump. Two men can 
work it and produce enough power to create a vacuum in the tank. The pump 
is connected to the dome by means of flexible pipe, and the gases arising by the 
exhaust of the air are forced to an upright boiler shaped stove and burned. The 
vacuum, of course, causes the material to rise from the cesspool and the tank is 
filled and carried away. None of the material i§ brought to view or comes in 
contact with any of the machinery, 



USE. 



691 



HANDLING WATER BALLAST IN SHIPS BY COMPRESSED AIR. 

Among the recently discovered uses for compressed air is that of handling 
the water ballast of ships. As is well known, modern vessels are provided with 
an inner water tight floor or bottom, usually placed four or five feet above the 
keel, forming with the shell a double bottom which strengthens the vessel, and 
makes it safer against leaks. 

The space between the bottoms is divided into a number of compartments, 
into which water is flowed for use as ballast. 

In order to trim ship it is necessary to vary the amount of water ballast or to 
shift it from one compartment to another. This has hitherto been done by means 




FIG. 265. 

of ponderous ballast pumps attached to a reservoir or "header" and connected by 
pipes with the various tanks. 

In Figs. 265, 266 and 267 we illustrate a system of ballast handling that dis- 
penses with the pumps and controls the ballast entirely by compressed air. This 
system is the pioneer of its kind, and is described in a patent issued Nov. 20, 1900, 




prntiC^^ 



FIG. 266. 



to George B. Wilcox, of Bay City, Mich. The system consists in omitting the ordi- 
nary ballast pump by which the water ballast is usually controlled, and using an 
air compressor to force air into the tank to be emptied, thus displacing the water, 
which flows out into the water header and thence either into another tank or 
overboard, as* desired. 

A compressed air reservoir or header similar to the water ballast header is 
provided, and each tank is connected to the air header by means of an air pipe. 
Suitable valves permit the discharge of air into the tanks in any desired combi- 
nation. Owing to the high velocity of the air a large volume of water can be 
displaced by means of a small air pipe. 



692 



USE. 



The advantages of this system are that the water ballast can be shifted at will 
from one tank to another without pumping any water overboard and without tak- 
ing in harbor water. The location of the air compressor is not confined to the 
line of the discharge pipe as ballast pumps must be. With this system the ballast 
water does not pass through pump valves, but has a free flow and the frictional 



If 



c5auk n*^4. 




FIG. 267. 



resistance of valves and the danger of blocking them by refuse is eliminated. An 
air compressor is very much lighter for a given capacity than the ordinary ballast 
pump, and will work with about ten times tlje economy of the ballast pump, be- 
sides being available for operating deck hoists, capstans, ash hoists, repair tools, 
etc., when it is not being used for handling the water ballast. This system is the 
subject of the first patent ever granted for a pneumatic ballast handling system, 
and will doubtless soon come into general use. 



r 



USE. 693 

PUMPS VS. COMPRESSORS FOR SHOP USE. 



We had thought that everybody was convinced of the fact that air for shop 
use cannot be economically compressed in air-brake pumps, but if the May meet- 
ing of the Central Railroad Club is correctly reported in the Buffalo papers (and 
these reports are usually official), a committee submitted a report on air-brake 
testing plants in which they advocated the use of pumps instead of compressors, 
on the score of economy, and in the discussion that followed, Mr. Higgins, of the 
Lehigh Valley, and Mr. McKenzie, of the Nickel Plate, were the only dissenting 
parties. 

Unfortunately for the committee, if their opinions are correctly quoted, it 
can easily be proven that it is economy to replace even a single pump with a com- 
pressor, and, in testing plants adjacent to shops where air can be used for other 
purposes also, thus requiring the capacity of several pumps, their use instead of 
compressors is extremely wasteful. 

Comparisons between the large steam-air compressors and pumps have been 
made in the past, but we are not aware that any attempt has been made 
to show the relative economy of pumps and small steam or belt com- 
pressors. For that reason it may be well to inquire into the matter. Two 
years ago the writer made some tests of 8-inch brake pumps in which it 
was found that for every pound of- steam passing through the pumps there was 
on the average about 2.25 cubic feet of free air compressed to 70 pounds pres- 
sure. For every 1,000 cubic feet of air compressed there is therefore required 445 
pounds of water, and if the evaporation of the boiler supplying the steam is taken 
at 8, the coal required is 55.6 pounds. The capacity of one 8-inch pump with 80 
pounds of steam is about 1,000 cubic feet per hour, and if we assumed that the 
pump ran the equivalent of 10 hours per day for 300 days in a year, the annual 
coal consumption is 55.6 X 10 X 300, or 83 tons. As it is seldom that a single 
pump is of sufficient capacity for a yard or shop, and as even the smallest belt 
compressors are usually of the capacity of two such pumps, we will first make a 
comparison on the basis of 2,000 cubic feet of free air compressed per hour, requir- 
ing two pumps consuming 166 tons of coal per year. It might here be remarked 
that as the speed of pumps vary considerably with slight differences of pressure, 
it may reasonably be urged that one pump might be made to do this work if higher 
steam pressure were used ; but if this is done the coal consumption is not altered 
materially, nearly the same amount of steam passing through one pump instead 
of two. 

In considering compressors of small capacity, those driven by belts must 
not be overlooked. We find by investigation that in this type about 2.8 horse 
power is required at the belt for each 1,000 cubic feet of air compressed per hour. 
If the shop engine consumes 35^ pounds of coal per horse power per hour and the 
loss in transmission by shafting, belts, etc., is 40 per cent., the coal per horse power 
at the compressor becomes 3.5 ^ .6 = 5.8 pounds, and for compressing 2,000 cubic 
feet of air it is 2.8 X 2 X 5.8 = 32.4 pounds. For a year of the same number of 
hours as before, the consumption is 32.4 X 10 X 300 = 485^ tons. 

In a steam compressor the horse power per 1,000 cubic feet of air com- 
pressed, including the internal friction of the engine, we will take as 3.2, though 
it will vary somewhat with the construction of the compressor. In one having 



694 



USE. 



only 2,cxx) cubic feet capacity per hour, a horse power cannot be expected on less 
than 4y2 poiuids of coal with the evaporation we have assumed, and it might easily 
be more. Taking it at that figure, the annual consumption would be 3.2 X 2 X 4.5 
X 10 X 300 = 43 tons. 

Now a belt compressor of 2,000 cubic feet capacity per hour and provided 
with an automatic regulator or governor, can be bought for from $200 to $250, 
and a steam compressor of that capacity will cost in the neighborhood of $350. 
Two brake pumps, even if they are not new, will represent an investment of from 
$100 to $200, according to their age. The comparison between the two types of 
compressors and the pumps might be summarized in tabular form thus : 

TABLE 67. 





Value of 
invest- 
ment. 


Coal con- 
sumed in 
tons, per 
annum. 


Cost of 
fuel, per 

annum, 

at $1 per 

ton. 


Saving 

per 
annum. 


Saving 

capitalized 

at 6 per 

cent. 


Two second-hand pumps 


$100 
225 
350 


166 tons 
43 " 


$166 50 
48 50 
43 00 






One belt compressor 


$117 
123 


$1,958 
2,050 


One steatu compressor 





From the columns showing the annual saving and the same capitalized at 6 
per cent., it will be seen that if the air-brake pumps were to be had for nothing it 
would still pay to buy the compressors if they cost less than $2,000. Perhaps a 
more striking way to view it is that if a road were offered two pumps and a 
bonus of $1,500 with them, their use to be confined to pumping air for shop use, 
it would be wise to refuse the offer and to purchase a compressor at market 
prices. If only one pump were needed it would still pay to buy a compressor of 
the size mentioned above, and the saving per year in fuel would still be more than 
$50. 

We think the above figures are fair and not in the least exaggerated. If 
anyone is disposed to quibble over some of the items, let him consider what the 
comparison would become according to his own figures if coal were at the same 
time taken at, say, $2.00 per ton, a price which many pay for it. 

The figures seem to prove conclusively that though the air-brake pump 
is admirably adapted for the service which it was designed and is almost beyond 
criticism when on an engine, it is in the wrong place when compressing air for 
shop uses. If managers, purchasing agents and others who wield the blue pencils 
that occasionally disfigure requisitions, could be made to realize these facts, there 
would be more compressors purchased, for many officials in the mechanical de- 
partments who know the wastefulness of pumps cannot induce their managements 
to purchase compressors. 

Before closing, we might make a brief comparison between a compressor, 
with a capacity of about 18.000 cubic feet of free air per hour (a favorite size with 
some roads), and pumps of the same capacity. On the same basis as the previous 
comparisons, but assuming that the compressor can furnish a horse power on four 



USE. 



695 



pounds of coal, the annual fuel bill for the compressor would be $346, and of the 
pumps $1,500. This is not an ideal case, for we know of one company that had 
ten air pumps in its shops and now has in their place one large duplex compressor. 
The latter almost pays for itself in one year, with coal at only $1 per ton. — 
American Engineer. 



COMPRESSED AIR IN THE FOUNDRY. 



PAPER READ AT THE FOUNDRYMEN's CONVENTION, HELD IN PHILADELPHIA, MAY 12, 
1896, BY CURTIS W. SHIELDS. 

Compressed air has long been known as an ideal medium for power trans- 
mission, but its introduction into the arts has been slow, because of the general 
lack of knowledge of the subject, due in a measure to the limited experience had 
with it. 

It has been looked upon as being an expensive power at b^t — too much 
of a mystery and something to be avoided rather than encountered and mastered. 

In many cases cheap and badly designed air compressors are put in use, 
and where such machines have been designed to occupy a small space or to be 





FIG. 268. 

light in weight, compressed air is sure to cost a great deal to produce, and this 
has stood in the way of the general introduction of compressed air more than 
anything else. 

Only recently inventive genius has been turned toward the development of 
labor-saving machines which would use compressed air as a motive power. 

Since compressed air is now produced economically, owing to the many 
recent improvements made in the design and construction of compressing ma- 
chinery, the up-to-date plant without its air compressor in the power house is 
the exception. Devices for using air are being placed upon the market in rapid 
succession, and its field of usefulness has broadened until now it is practically 
indispensable in a great many operations, and its economic value is recognized. 

Under the ordinary conditions existing in foundries a belt-driven com- 
pressor is usually more favorably considered than one driven by steam. 

The ordinary shop engine of a good type gives better results for the 
amount of steam used than if the steam was used to drive a small compressor 
direct. ' 



696 



USE. 



A belt compressor fitted with a proper regulator absorbs only enough 
power to meet the demands of the work performed, and being run in connection 
with other machinery, its effect on the coal consumption is not noticeable. 

However, in many cases a steam-driven compressor is preferable, because 
a high class steam-actuated compressor uses steam almost if not quite as eco- 
nomically as a shop engine, and whatever loss there may be is more than made 
up for by the advantages of a steam-driven compressor. With them all shafting 
and belting are avoided, and the machine can be located in the engine room, 
where it can be under the care of the engineer. If installed in the foundry the 
dust and sand have a very appreciable effect upon the bearings and moving parts, 
and no matter how carefully housed, your compressor cannot be as well taken 
care of as though it were in the engine room. Frequently, when- a foundry has 
no steam power, the compressor can be located in a neighbor's engine room, and 




FIG. 269. 



power rented to operate it, as the air pipe can be run any desired distance quite 
readily and at small expense. 

Transmission of power by compressed air has the advantages of certainty 
and regularity in action; simplicity in machinery, freedom from the possibility 
of fatal accidents, and the assistance given to ventilation and in cooling the shop 
— these last being considerations of much importance in many cases. Works 
employing this method do not require the supervision of a specially qualified ex- 
pert, and the chances of interruption by accident through negligence are cer- 
tainly less than in any other form of power transmission. 

When we come to the question of laying out the piping for a foundry, it 
is well to keep this simple rule in mind. The head necessary to drive the air 
through the pipe is as the square of the velocity, and to obtain the best results 
the flow of air through the pipe should not exceed 20 ft. per second. If this is 
borne in mind, air can be conveyed almost any distance with little or no loss. 

The receiver should be placed in any convenient place, and should be of 
not less capacity than the rating of the compressor in cubic ft. of free air per 
minute. 

It is preferable to have the inlet pipe from the compressor enter the re- 
ceiver near the top and the outlet near the bottom, and at right angles to the 



USE. 697 

inlet. A drain cock at the lowest point should be provided, and a pressure gauge 
safety valve on the top is a great convenience. 

Too frequently no attention is given to leaks in the air pipes, as the air 
is not visible and causes no discomfort in its escape. Leaks, however small, 
should receive prompt attention if anything like economical results are desired. 

Leaks in air pipes are fortunately easy to find, because of the hissing noise 
caused by the escaping air. This point is an important one in comparing pneu- 
matic with electric transmission of power. 

Leaks in electric wires are hard to discover, and are usually found after 
some damage has been done. The current may be led away through the cross- 
ing of other wires, moisture, or frame of building if of iron, and occasions an 
unseen, though none the less undesirable, loss. 

A little thought and attention given to the elimination of turns and angles 
in the pipe mains will amply repay for the trouble. It is a great economy to lead 
the air mains centratly and then run smaller connections to points adjacent and 
convenient to place air is to be used. , 

If this is done, short lengths of hose pipe can be attached wherever most 
convenient for connection to hoists, sand-sifter, or other apparatus, or the air 
can be used for the same purposes that the bellows and brush are employed. 

The application of the air hoist to cranes may be made in an almost end- 
less variety of ways to meet the requirements of foundries. The most common 
types are simple cylinder hoists either vertical or horizontal, or in combination 
with a low pressure hydraulic system. In many instances direct acting hoists 
may be readily applied to hand-power cranes already in use, without in the least 
interfering with the gearing, and at a very small expense. 

In an air-hoist the power and load are brought together in the most sim- 
ple manner. A boy, with this aid, can lift a given load a dozen times while a 
gang of several men are operating a chain block or windlass. There is no noise, 
no jar, and the load is always balanced. In foundries where an overhead traveler 
cannot be installed, air hoists suspended from trolleys running on an overhead 
track answer very satisfactorily; and if hose couplings similar to those used in 
connection with the ordinary air brake are provided, by simply detaching the 
hose connection after load is raised, the hoist may be run on the overhead track 
to any desired part of the establishment. 

This is especially valuable in conveying flasks outside of foundry to stor- 
age sheds, patterns to pattern shop, or finished castings to machine shop. 

. Nearly every foundryman is conversant with the value of air-hoists in the 
foundry for lifting flasks and copes, drawing patterns and conveying cores to 
ovens. 

Few of us realize how cheap an air-hoist is to operate, apart from its con- 
venience and speed in handling loads. It has been estimated by Mr. Frank 
Richards that at 100 lbs. gauge pressure compressed air costs 5 cents per 1,000 
cubic ft. of free air. 

In a very, interesting article recently published, this gentleman figures the 
cost of operating a hoist as follows : "Suppose we have a hoisting cylinder 6 
inches in diameter, with a piston rod or hoisting rod i inch in diameter and 



698 



USE. 



capable of lifting 4 feet or more. Then, using air in the cylinder at an effective 
pressure of 90 lbs., the lift of the hoist will be (6''-i^) x .7854x90=2475 lbs. 

"If this weight is lifted, say 4 feet, the volume of air used will be: 
(6^-1'') X .7854 X 4-^i44=.7636 cubic ft. To this we add 30 per cent, to cover 
all possible contingencies : .7636x.229=.9926, and we will call this i cubic ft. The 
one loss that seeins to be inevitable, and which is included in our 30 per cent, 
allowance, is in taking up the slack of the hoisting chain, or other means of 
attaching to the load, before the hoisting actually commences, so that a certain 
portion of the cylinder must be filled with the compressed air, besides the actual 
4 feet of travel for the lift. As the air in the cylinder is up to a pressure of 90 
lbs. or 7 atmospheres, the volume of free air used will be seven cubic ft., and the 
cost of this will therefore be 7/1000, or .007 x.05=$o.ooo35, and this is all we 
have to pay for lifting more than a ton a height of 4 ft. A hundred of such 
hoists will be made, of course, for $0,035, or 3% cents. The accompanying table, 
which might be greatly extended and still not cover all th^ actual conditions of 
service, will be found of interest especially in the id^a that it conveys of the 
cost of air hoisting. It is probable that many persons will be surprised at the low 
figures." 

In connection with the low cost of air, it is to be remembered that the 
hoists are also simple and cheap. 

TABIvK 68. — AIR HOIST TABLK. 

A Table of the lifting capacities of direct acting air hoists, with volume of free air per lift, and 
cost of air per single lift and per 100 lifts, with a maximum lift of 4 feet, and a minimum 
pressure of 90 lbs. air furnished at 5 cents per 1,000 cubic feet of free air. 



^. 

U V 


re 


e1 


4^ . 


u 


u w 




PI 

it! (d 


an 


^ -2 !« 


'^ 


° 8 


.20 


W ^ 


i.^ 


^ .i: 


S p. 


1 s 


Q 


< 


6< 





a 


2 


3.05 


274 


74 


$0.000037 


10.0037 


3 


6.87 


618 


1.67 


.000084 


.0084 


4 


18.22 


1099 


2.97 


.000149 


.0149 


5 


19.09 


1718 


4.64 


.000232 


.0232 


6 


27.49 


2474 


6.68 


.000334 


.0334 


7 


37.42 


3367 


9.09 


.000455 


.0455 


8 


48.87 


4398 


11.88 


.000594 


.0594 


9 


61.85 


5566 


15.03 


.000752 


.0752 


10 


76.36 


6872 


18.56 


.000928 


.0988 


11 


92.39 


8315 


28.46 


.001123 


.1183 


18 


109.96 


9896 


26.73 


.001337 


.1337 



FRANK RICHARDS. 



Air used in combination with a low pressure hydraulic system gives 
the best results for heavy loads. By interposing the water between the elastic 
medium air and the load, we eliminate that element of danger which otherwise 
would be present in handling vessels of molten metal, as. in foundry practice, and 
also obtain a sort of elastic positiveness which is so essential and desirable. In 
the actual work of molding, as in lifting copes and molds, drawing patterns and 
moving cores, the men are enabled to do about 50 per cent, more work and do 



USE. 



699 



ii easier and better, when equipped with a hydro-pneumatic hoist. Included in 
this percentage is the saving in repairs and the danger of losing castings. These 
hoists more nearly approach the old-fashioned hemp rope cranes in their elas- 
ticity, as the compressed air behind the water seems to impart this peculiar 
quality. All danger of the liquid freezing is overcome by using a non-congealing 
compound or a little glycerine, wood alcohol or chloride of magnesium added 
to the water. 

In addition to operating movable hoists, air has proven its value for con- 
veying pig iron to the top of the cupola, and for breaking up scrap by lifting a 
heavy weight which is dropped some 15 or 18 ft. This pig-breaker broke three 




FIG. 270. 



half pigs into three pieces each in one minute, and can easily break twenty tons of 
pig while a man is breaking up one ton by the old sledge method. A portable 
pneumatic drilling machine for boring holes to weaken stiff castings is used to 
advantage in connection with this breaker. 

The product of a molding machine can be greatly increased if the handling 
of the sand in shovels is done awa}"^ with. This is accomplished by an air jet 
which at 60 lbs. pressure will lift 100 lbs. of sand per minute 20 ft. high. A 
quarter-inch nozzle will use go cubic ft. of free air per minute doing this duty. 
By elevating the sand to a bin overhead and then conveying it in a chute or pipe 
directly over the molding machine, much time and labor can be saved. 

A simple slide in the pipe forms a ready means of regulating the amount 
of sand served to the machine for each mold. 



700 



USE. 



In a foundry where the air pipes have been led as previously indicated, and 
hose connections located at convenient points, the portable pneumatic sand-sifter 
is indispensable. In this machine a small amount of air operates a rotary motor 
which drives gearing connected to the sieve. Air admitted through an ^^ inch 
opening at a pressure of 70 lbs., developes sufficient power to do the heaviest 
work. 

Recent observation of a molding machine in operation at the foundry of 
the Ingersoll-Sergeant Drill Company of Easton, Pa., gave the following figures : 

On rock drill cylinders, three helpers operating a duplex machine can turn 
out 22 per day. It formerly took four molders to make this output. 

In other words, to do the work by hand now being turned out with the 
aid of the molding machine operated by compressed air, would cost 100 per cent, 
more than is being paid now. 

On rock drill steam chests, same machine, operated by two helpers, pro- 
duces 66 molds per day. Formerly it required three molders to equal this num- 




FiG. 271. 



ber. In this case it would cost 125 per cent, more to turn out the same product 
by old method. 

The economy of the sand blast for cleaning castings was quite as marked 
as that of the molding machine. On a flask 30" x 14" x 5", made without using 
any facing, no difficulty was experienced in cleaning 6 sq. ft. of surface per min- 
ute. A box bed plate, weighing 1,700 lbs., was cleaned in one hour by the blast, 
while another bed plate made from the same pattern, took three hours to clean 
by hand. With the blast the casting was cleaned so that the chipper did not 
have to do any cleaning as he had to do when blast was not used. Neither 
brushes nor files will get around fins and risers as the blast does. 

A very difficult casting with cores that are almost impossible to get out 
by hand, was cleaned in 45 minutes by the blast, as against 2 hours and 40 min- 
utes by hand. 



USE. 



701 



In this same foundry they formerly melted about 5 tons of iron per day 
and employed 14 molders, 8 core makers, and a cleaning and chipping gang of 7. 

They have practically doubled their plant and now pour 10 to 12 tons per 
day and employ 27 molders, 12 core makers and a number of labor-saving devices 
to increase their output, but the same cleaning gang of 7 men, with the addition 
of a sand blast, take care of the product, and the cleaning is done in a much 
better manner than previously. 

The sand blast not only effects a great saving in the actual cost of the 
castings, but a further saving through the removal of the oxide which is so 
destructive to tools in the machine shop. 

This saving on tools is most apparent where the work is milled, as cutters 
can be run at an increased speed. The sand blast applied to the tumbling barrel 
is an improvement worthy of notice. 

Aside from the economical features connected with the use of the sand 
blast, it cleans the castings far better than by hand, and where a casting has in- 




FIG. 272. 



tricate steam or air passages, it is of the greatest importance to be able to thor- 
oughly clean these inaccessible parts. 

Associated with the sand blast the pneumatic chipper shows to good ad- 
vantage. 

These tools were formerly too delicate and complicated for foundry uses, 
but recent improvements have so simplified their construction that they now have 
only three pieces in their entire make-up, and but one of these is a moving part. 

Dark foundries have found the Wells, Lucigen, or some similar light of 
great use where a cheap intermittent light was needed. In these lamps com- 
pressed air forces oil through a nozzle forming a spray, which when ignited give? 



702 USE. 

a flame about 5 inches in diameter and 30 inches long, and of about 1,000 candle 
power. 

The air is used at a pressure of from 10 to 30 lbs., and one gallon of oil 
and 60 cubic ft. of free air per hour suffice to operate the lamp. 

These hydro-carbon burners are very useful for skin-drying large molds 
as well as for lighting. 

Breaking test bars from each cast is another use to which air has been 
applied. 

A comparatively small air compressor of proper construction and design 
will furnish sufficient air for all the needs of a foundry of ordinary size. 

An illustration in point is a foundry running 4 cranes of 20, 10, 8 and i 




FIG. 273. — WOI.STENCROFT PNEUMATIC CHIPPER. 

ton capacity respectively; a sand blast, 2 pneumatic chippers, i duplex molding 
machine and for blowing out and dusting molds in process of construction. 

In addition, the machine shop uses air for testing small engines and blow- 
ing out cylinder ports and inaccessible parts after machining, to get rid of oil 
and chips, and for bench dusting and copying letters* in the office. 

Air at 60 lbs. pressure for all these uses was supplied by a 14 x 16 x 18 
compressor, running at 120 revolutions per minute and furnishing about 500 
cubic feet of free air per minute. 



COMPRESSED AIR AND ITS ECONOMIES IN THE FOUNDRY. 

Perhaps in no other operation in the foundry is air used to such good 
advantage as in hoists and cranes. By using direct acting hoists suspended from 
trolley tracks and using detachable air hose couplings, a casting or other weight 
can be readily conveyed to any part of the foundry, or carried outside the foundry 
building to the machine or pattern shop, or in fact to any point around the estab- 
lishment that may be desired, thus covering a field vastly wider than is possible 
with a traveller alone. 

The great economy of an air hoist is well illustrated in the following 
record of actual work performed in the foundry of Messrs. Russell & Co., of Mas- 
sillon, Ohio. 

In making wheels for their traction engines, a molder and helper formerly 
made one mold per day of a wheel 16 inches face by 66 inches diameter. During 
the entire operation of molding and pouring, 104 hoists and lowers were neces- 
sary. With the old crane it took these two men from five to six minutes to turn 
a flask when assisted by a laborer on the windlass. Now, with the air hoist, the 
laborer is done away with, and they turn a flask in two minutes. This saves in 



Ii 



USE. 703 

time alone 52 times 3J^ minutes, or three hours per day, and the molder and helper 
make two 58-inch by 12-inch wheels in addition to the large wheel, which formerly 
constituted a day's work, in the time saved in moving by the air hoist. 

In this same foundry a test of one of their jib cranes gave the following: 

Area of piston, 452.39 square inches (24 inches diameter). 

Height of lift, 6 feet. 

Hoist, 2 feet to i foot of piston travel. 

Weights lifted, 2,000, 4,000, and 5,000 pounds. 

Main air receiver gauge, 100 feet from crane, registered 63 pounds pressure. 

Gauge on hoisting cylinder, 30, 40 and 45 pounds for the respective hoists. 

It was found that it took ten pounds pressure on hoisting cylinder gauge to 
overcome all the friction of the chains wrapping around the sheaves, as well as 
the packing in the stuffing box of piston rod and the frictional resistance of the 
piston against the cylinder walls. 







Deducting 4523.9 lbs 






as being amount 


Weight lifted 


Preesure on 


required to over- 


6 feet. 


Piston. 


come all resistance 

except 

load, we get 


2,000 lbs. 


6785.85 lbs. 


2261.55 lbs. 


4,000 " 


9047.80 " 


4523-9 " 


5,000 " 


10178.77 " 


5654.87 " 



The excess of 261.55, 523.9, and 654.87 lbs. in the respective cases, is, no 
doubt, due to the fact that the chains are hugging the sheaves tighter under the 
loads than when empty; and this increased friction must be overcome at the ex- 
pense of pressure. The ten pounds required to overcome the load and frictional 
resistance of the chain, chain block, etc., in the crane itself, is not altogether 
wasted, for the space in the cylinder between the piston and the head on the lifting 
side being once supplied with this amount, is then ready to do useful work. A 24- 
inch cylinder with piston moved 3 feet, would contain 28,275 cubic feet of free air 
if the gauge on the cylinder showed 30 pounds, or two atmospheres pressure, and 
ten such hoists would use 282^ cubic feet of free air. This amount of air would 
not cost over one and one-half cents. With compressed air at five cents or less 
per 1,000 cubic feet of free air delivered at 100 pounds pressure, this is vastly 
cheaper than a gang of men, on a windlass, with the molders standing idle an 
indefinite time. The frictional loss in direct air hoists has been shown by tests 
made by the Whiting Foundry Equipment Co. not to exceed 15 per cent. A lot of 
12 hoists taken at random showed a varying loss of from 9.2 to 23 per cent., aver- 
age 12.9 per cent. loss. Another lot of ten averaged 14.65 per cent. loss. 

Mr. Chas. O. Heggem, the well-known compressed air expert, uses com- 
pressed air for breaking test bars, and at the same time automatically recording 
the shrinkage and deflection. The pattern for the test bars is 24^^ inches long, 
and in the case of a bar tested, the register showed a shrinkage of 9-64 in. to the 
foot; deflection, ^ in. in 24 inches; and the bar, which was i in. square, broke 
under a pressure of 1,375 pounds. 

In view of the great variety of ways (more or less unsatisfactory) of test- 
ing the qualities of iron as expressed last May at the meeting of the founcjrymen 




704 USE. 

in Philadelphia, Pa., it would appear that the majority of foundries using air could 
adopt Mr. Heggem's idea with advantage. 

Compressed air cranes have many advantages over those electrically driven 
for foundry work, as the dust and heat which materially affect the efficiency of 
electric motors have no appreciable effect on the air motors. 

Few if any of the compressed air driven machines that have been intro- 
duced for foundry work serves a better end than the sand blast. By its aid, cast- 
ings that were hitherto cleaned with the greatest difficulty can now be cleaned 
in a remarkably short time, and with a tithe of the exertion formerly necessary. 
For instance, a casting which was made with a core that was almost impossible 
to get out satisfactorily, and which took 45 minutes to clean by hand, was cleaned 
by the sand blast in 16 minutes. Six and one-half minutes of this time was occu- 
pied by chipping out a fin to allow the blast to reach the core. 

The waste sand from a sand blast can be used to advantage in making cores 
when mixed with the core sand in proportion of about i to 4. 

Another important use of compressed air is in connection with the molding 
machine. 

By its use the expense of stripping plates is entirely done away with, and 
by using an air jet to blow sand from the pattern instead of using a bellows and 
brush, much time is saved. The use of air permits the molding machine to be 
moved to any part of the foundry, and it is decidedly cheaper to bring the mold- 
ing machine to the sand pile rather than wheel the tons of sand to the machine. 

A deeper draft is possible using air than can be obtained with a steam- 
actuated machine. In general, a molding machine operated by compressed air 
is portable, independent of any foundation, and can be connected to the air main 
by a hose and used in any part of the foundry, which is not possible when using 
steam. It makes molds without the use of stripping plates, in fact uses ordinary 
split-wood or metal patterns fastened by wood screws to the pattern plate. This 
is accomplished by the use of an automatic rapping attachment which frees the 
pattern from the sand, without any amplitude of motion in the pattern, while it 
is being drawn. This compressed air molding machine weighs and costs but little 
more than a hand machine, and has all the advantages in point of output and size 
of flasks of power machines. Observation of an air-actuated molding machine 
operated by two helpers at $1.50 per day each, showed that on certain work, con- 
taining 12 small cores per mold, they put up 50 molds per day. Formerly it took 
four helpers, at the same wages, to make 50 molds by hand per day, thus gaining a 
saving in wages of 50 per cent. 

In another case, on new work, the first day two helpers at $1.50 each per 
day, turned out 35 molds. The best record on this work for a molder working by 
the piece was 7 molds per day. 

The product of a molding machine can be greatly increased if the handling 
of the sand in shovels is done away with. This is accomplished by an air jet 
which at 60 lbs. pressure will lift 100 lbs. of sand per minute 20 feet high. A 
quarter-inch nozzle will use go cubic feet of free air per minute doing this duty. 
By elevating the sand to a bin overhead and then conveying it in a chute or pipe 
directly over the molding machine, much time and labor can be saved. 

A simple slide in the pipe forms a ready means of regulating the amount 
of sand served to the machine for each mold. 



USE. 705 

After deciding to adopt compressed air as a labor-saving aid in the foundry, 
the most important points for consideration are the type or style of compressor to 
install, and its size or capacity. Only too frequently, confined space, together 
with a disinclination to expend more than will barely suffice for present needs, 
act as a handicap and incline the founder to decide upon a plant that "will do 
somehow," rather than one that his cold, unbiased judgment would dictate as be- 
ing best suited to his needs. It is the exception to find a plant too large even for 
present needs, for while starting out with the best intentions to allow for a 
reserve, the ingenious foundrymen originate so many little labor-saving shop 
kinks that before long there is a demand for more air, and the engineer is told to 
"speed her up a few turns." 

When it is decided to use air hoists, cranes, molding machines and other 
air-actuated machinery, it is imperative to bear in mind that if the air supply 
stops through breakdown or insufficient capacity, the whole foundry is practically 
at a standstill. If there is no air to operate the hoists, the men cannot handle 
their work, and great loss ensues. 

It is clearly of the utmost importance that the source of air supply must be 
adequate to all reasonable demands and must be of such staunch and durable de- 
sign and construction as will insure its ability to easily meet the increased duty 
when called upon to "speed up a few turns." These "few turns" usually mean 
about 20 per cent, increase, and it is only the very best high duty compressors 
that will survive such a test. 

It is an open question, which must be largely decided by the individual 
conditions in each foundry, whether a steam driven or belt compressor is most 
desirable. When there is shafting already in the foundry and a good dust-tight 
room can be provided, it is perhaps cheaper to put in the belt driven type. The 
steam compressor has its advantages, however, as it can be located in the engine 
room under the supervision of the engineer, and the necessity for shafting and 
belting obviated. As the best steam-actuated compressors now use steam very 
nearly if not quite as economically as the majority of shop engines, low efficiency 
cannot be urged against their use with the same force as formerly. 

The steam machine can be run at a speed to suit the requirements of the 
foundry by regulating the throttle. Curtis w. shields. 



A MODEL COMPRESSED AIR FOUNDRY PLANT. 

The value of compressed air for operating small motors on isolated and 
moving apparatus, especially when power is used for perhaps a minute or so in 
every ten, is beginning to be appreciated in this country as it should be, and hardly 
ci week passes that does not record some valuable addition to the list of new appli- 
cations of this nature. 

This progress would be much faster but for the fact that usually a change to 
air power involves a considerable outlay for new machinery and the discarding of 
I he old type, which may be in good or perfect condition. 

A neat avoidance of this objection is shown in Fig. 274, which illustrates a 
foundry crane in the works of John J. Radley & Co., structural iron manufac- 



7o6 



USE. 



turers, New York City. This was originally made to be operated by hand, but to 
it has been attached an air motor without changing the original gearing in the 
least, so it may at any time be operated either by hand or air. 

The motor is reversible and of the direct acting piston type. Its economy 
in the use of air is best illustrated by stating that the air compressor is stopped at 
the end of the day's work, with the air receiver (which is in this case a large 
boiler) fully charged, and sufficient air is thus stored to draw all their castings in 
the evening without running the compressor. 

These progressive Founders are, we believe, the first to successfully apply 
this method to every-day shop practice ; and the fact that they have proven this 




FIG. 274. — COMPRESSED AIR MOTOR ATTACHED TO FOUNDRY CRANE. 



possible should effectively remove the objection that has sometimes been raised, 
that it is "so hard to keep air from leaking away." If they do not use any air in 
the evening, they find nearly the same pressure on the gauge in the morning as 
when the compressor was stopped, which shows that joints can be made tight and 
that compressed air is favorable to keeping them so. 

This little motor, which weighs less than 200 pounds, easily lifts 8,000 pounds 
ten feet per minute, and by changes in the gearing can be made to lift almost any 
load, in use it is protected by a sheet-iron case to keep out dust. 



USE. 



707 



These motors are used on traveling cranes for lifting the load and for 
moving the traveler along the track, and are well adapted to any light derrick 
work. For many purposes they are preferable to straight lift hoists, because they 
are not limited in the height of lift; use air only in proportion to distance load is 
lifted; hold load in constant position; do not jump up when part of load is 




FIG. 275. — CYLINDER HOIST ON FOUNDRY CRANE. 



removed, as in pouring molten metals ; will do delicate mould work safely, and 
can be placed in close quarters where a cylinder hoist could not be used at all. 
For operating any light machine where it is inconvenient to get a belt, they should 
be very useful. 

Fig. 275 shows another air crane in this same foundry, which embodies some 
original ideas of the owners, the chief one being the method of connecting the 



7o8 USE. 

ropes; one end of the hoisting ropes is connected to a Whiting Foundry and 
Equipment Co.'s Cylinder Hoist, carried out to the lifting sheave and back to a 
hand windlass on the mast. This windlass works on one end of the rope, or the 
air cylinder on the other end; so this, too, is either a hand or air crane at will. 
The ladle suspended on this crane is also of the improved Whiting make. 

These people also use a Haeseler Portable Compressed Air Breast Drill for 
boring test holes in cast iron columns. 

Ample power for all these appliances is furnished by lo-inch belt-driven air 
compressor, which when air is not being used, automatically unloads itself, taking 
power only in proportion to the work being done in the foundry. 

This entire compressed air equipment was furnished by the Ingersoll-Ser- 
geant Drill Co., Havemeyer Building, New York City. h. m. perry. 



THE USE OF COMPRESSED AIR AT A BLAST FURNACE PLANT. 

When "A" Furnace of the Maryland Steel Co., Sparrow's Point, Md., was 
blown in for its second blast (November, 1895), a compressed air plant was put 
in, and has been used with much success during the past year. Compressed air 
is used for the tap-hole drill, the tap-hole "gun," the transfer-table at the scales, 
the turn-table on top of the furnace, and for lifting the rails of the turn-table in 
running off the empty cars. 

The compressor (a Rand direct-acting steam air compressor) and the re- 
ceiver are set up in the pump-house, and are cared for by the pump man. The 
air-pipe from the receiver to the furnace is about 500 feet long; there the pipe 
branches to the different machines. Last winter the air first passed through a 
coiled pipe heated by a coke fire near the scales, in order to keep the moisture in 
the condensed air from freezing. The piping at the furnace is so arranged that 
steam can be used for all the machines in case the compressor breaks down, and 
on the transfer-table hydraulic pressure also can be used. The pipes and valves 
are so arranged that air or steam can be used on any or all the machines, and so 
that all the pressure can be put on any one machine. 

The tap-hole drill is a Little Giant rock drill so mounted as to swing into 
place and drill out the tap-hole without any hard manual labor. This arrange- 
ment is the device of Superintendent David Baker, and is described by him in 
Trans. Amer. Inst. Min. Eng., vol. xxi. The supporting crane has been much 
changed since that description was written, and now consists of the simple and 
light crane shown in the photograph. The crane is fastened to one of the col- 
umns at the side of the tap-hole so that the drill can be swung back out of the 
way when not in use. The air-pipe is connected by swing joints and an expan- 
sion sleeve, which can be seen in the photograph (the drill is in place ready to 
open the hole, the "gun" is loaded and ready to swing into place). 

Formerly steam was used to run the drill, but it has several disadvantages 
which air has not. Great care had to be taken to prevent the condensed steam 
from dripping into the iron trough and perhaps causing a "boil." The escaping 
steam would make it hot for the men, and the clouds of vapor would often pre- 



USE. 



709 



vent them from watching the work well. A hose for the exhaust was necessary, 
and this made another part to care for, and it was sometimes burned. In cold 
weather there would be much conde'nsing and loss of power. Compressed air does 
away with all these difficulties. 

The tap-hole "gun" is Mr. S. W. Vaughen's patent device for shutting the 
tap-hole by power, thus saving much hard, hot work for the men, and doing away 
with the necessity of taking the blast off the furnace after each cast to shut the 
tap-hole. 

An illustrated description of an early form of this gun is given in the Iron 
Age, Nov. 21, 1895. The gun shown in Figs. 276 and 277 has a "breech" for load- 
ing, a compact valve, and a simple and adjustable mounting. It is made of cast 
iron and consists of two cylinders and a piston rod with a piston on each end. The 
air end of the gun is an ordinary air-cylinder operated by a hand valve. The 
clay "barrel" is open at the "nose" end, and has a "breech" at the other end (see 
Fig. 277). The gun is suspended on a crane fastened to the column opposite the 




FIG. 276. 



drill. The crane is similar to the drill crane, and the air-pipe has swing joints 
and a rubber hose connection to allow freedom of motion. 

The gun is loaded with about 35 clay balls before the cast, and when the 
iron is all out of the furnace the gun is swung around and clamped into place 
and the whole charge shot into the tap-hole at once. By reversing the valve the 
piston is brought back; the breech is opened, the clay barrel loaded up again and 
more clay shot into the hole till it is completely shut up. 

Here the air has the same advantages over steam as in the drill. About 
65 to 70 pounds air pressure is needed for the drill and gun. If at any time there 
is not enough pressure to run the drill well, a signal is given from the furnace 
to the pumpman, and he sets the escape valve of the receiver for higher pressure. 

In order to have rapid handling of the ore, limestone, and coke, buggies 
which have four wheels, run on tracks, and hold from 1,500 to 2,300 lbs. of stock, 
at the scales, a transfer table is placed between the scales and the elevator. When 
the empties come down they are run off from the elevator onto the transfer 
which is run to one side ; then the loaded cars on the scales are pushed across the 



710 



USE. 



transfer, which is provided with seven sets of rails running crosswise, onto the 
cage of the elevator. This transfer is operated by compressed air, and is provided 
with water cushions at either end to permit rapid running and to take up the 
shock. At present the compressed air is obtained from the regular blast main of 
the furnace, which averages lo or 12 lbs. pressure. When the blast is off the 
furnace, hydraulic pressure of 26 lbs. is used in the same cylinder, but it is too 
slow for regular work. At first the transfer was run by air at 60 to 70 lbs. 
pressure from the compressor, using a smaller cylinder which can now be used in 
case of any break-down of other parts. 

The turn-table on top is a part of the filling arrangement necessary to give 
an even distribution of the stock as it is dumped into the furnace. It has a track 
on each side holding two buggies at once, so that two buggies are dumped on one 
side, and the next two buggies on the other side. On every other "charge" the 
turn-table with the loaded buggies on it is turned about 75 degrees, and then the 







FIG. 277. 



stock is dumped. Air from the compressor is used for this table, and has proved 
more suitable than steam, especially in cold weather. 

The two tracks which extend across the turn-table are arranged so that 
the back ends can be raised by pistons working in compressed air cylinders. 
When the ore is dumped the rails are raised, and the empty buggies run back 
onto the cage with a little help from the men. Air from the compressor runs 
these lifts also. 

'i'he blacksmith's forge, in a shop near the pump-house, is ordinarily run 
by blast from the furnace blowing engine; but if the furnace is stopped for any 
reason, blast for the forge can be taken from the receiver of the air-plant. 

Thus the air compressor has become a valuable machine at the furnace. 

The trouble from condensed moisture in the different machines was largely 
due, I think, from the fact that the compressor takes its air directly from the 
pump-room which is always warm and moist. I here suggest that much better 
work would be done if the air were taken directly from outdoors. 

RALPH H. SVVEETSER. 



I 



USE. 711 

BRIEF HISTORY OF LIQUID AIR. 

As the subject of liquid air and low temperature is receiving so large an 
amount of attention and thought in the scientific world to-day, a brief history of 
its production may be considered timely. Prior to 1877 air was thought to be a 
permanent or incondensable gas, but it was liquefied simultaneously by Messrs. 
Pictet and Cailletet at that time though at an enormous expense. About 200 
years ago the lowest temperature thought to be obtainable was produced by a 
mixture of snow and ice and was used by Fahrenheit in establishing a zero for 
his thermometric scale. Since that time scientists have reached a temperature 
some 400 degrees below the lowest point ever reached by Fahrenheit. Of the 
three known methods for producing cold, the first, i. e., by the rapid solution of a 
solid, was used entirely up to 1820 and yielded a temperature of 50 degrees below 
zero centigrade. The other two methods are the rapid evaporation of a volatile 
liquid and the rapid expansion of a cooled and compressed gas. By a combina- 
tion of pressure and refrigeration, Faraday in 1823 liquefied all except six of the 
existing gases, but it was not until 1869 that it was discovered that these gases 
must first be cooled to a critical temperature. By subjecting hydrogen to an 
enormous pressure and at the same time lowering its temperature it was found 
possible to liquefy it. Hydrogen has a critical temperature only ss degrees c. 
above the absolute zero of temperature. From the experiments performed, the 
conclusion was drawn that solids, liquids and gases were but different forms of 
matter through which any substance could be made to pass by the addition or 
withdrawal of heat and pressure. The liquefaction of air economically and in 
large quantity has only recentl}'^ been accomplished. — The Engineer. 



LIQUID AIR. 

The subject of liquid air has of late attracted considerable attention, and in 
view of some erroneous statements which have become widely circulated, a few 
remarks in correction of such errors would seem timely. 

Ordinary atmospheric air is nothing more or less than the super-heated 
vapor of a liquid, and the boiling point of air at about this liquid, is 312° F, 
This is probably the most reliable temperature of the boiling point of liquid air, 
being that obtained by Wroblewski, and quoted in Prof. De Volson Wood's ther- 
modynamics. Much lower temperature can be obtained by evaporating liquid air 
in vacuum. 

It should be noted that the boiling point of liquid air is lower than the 
boiling points of either of its principal constituents. Although some very credi- 
table work of investigation in the subject of liquid air has been done in Europe 
by Dewar, Wroblewski, Olszewski, Pictet, Cailletet and others, comparatively 
little is definitely known of the chemical and physical properties and effects. 

The physical effects of the low temperature of liquid air vary, but in 
general makes all substances very hard and brittle. While in the case of some 
metals the tensile strength is increased, the elasticity seems to have been destroyed. 
Heavy sheet iron becomes so brittle that it may be readily mapped in pieces with 



715 USE. 

the fingers, and the fracture exhibits a finely crystaline structure. Gum rubber, 
meats, vegetables and other substances become hard and brittle enough to be 
broken in fragments by the hand. Ice, at this low temperature, crumbles into 
small pieces, and resin under slight pressure falls down in the form of a powder. 
Oils are readily solidified. 

It would seem that some substances are brought almost to the point of 
disintegration, and the above examples are merely cited to give a slight idea of 
the various effects which this low temperature has upon the physical properties 
of matter. 

Chemical affinity at this low temperature is apparently destroyed, and sub- 
stances which combine violently at ordinary temperature have no effect upon each 
other in liquid air. From the laws of electricity, we know that if a conductor 
were immersed in liquid air the low temperature would cause it to have practi- 
cally no resistance. 

It has been stated that the flesh, if immersed in liquid air long enough to 
come in contact with it, would be burned, the same as if it were exposed to a 
high temperature. This is erroneous, for while the nervous sensations are the 
same, the two effects are quite different, the high temperature producing a burn 
and the low temperature a freeze, which when produced by such a low tempera- 
ture, is much more painful than a burn. 

It has been stated that "a handkerchief of silk, linen or cotton, saturated 
with liquid air, will be charred and destroyed just the same as if it were put in an 
oven and browned, though no change of color is apparent." This is also erron- 
eous, as the fibre is merely frozen by the low temperature, and if allowed to re- 
main undisturbed and return to the normal temperature again, is not harmed in 
the least. But, if when in the frozen condition it is crumpled up and crushed, 
the fibre will be broken and destroyed. The statement that the vapor of liquid 
air when mixed with atmospheric air in certain proportions can be used for illu- 
minating purposes seems to have been given considerable credence. The vapor of 
liquid air is nothing more or less than cool atmospheric air, and how two quan- 
tities of air mixed together will produce illuminating gas, is not plain to the 
writer. 

In all the articles that have been written concerning liquid air, the work of 
Charles E. Tripler, of New York, has been entirelj'^ ignored, and this is surpris- 
ing, in view of the fact that he has devoted his entire time for the last twenty 
years to this line of investigation, and has brought the apparatus to a greater 
state of perfection than any one else, and developed the subject to the point of 
commercial practicability. 

During the past summer Mr. Tripler took a can of liquid air from New 
York to both Washington and Boston, starting with about four gallons in each 
instance. After being in transit eight or nine hours, not over twenty-five per 
cent, was lost in either case. 

The apparatus accredited to Prof. Linde and described in the August num- 
ber of Compressed Air, ia identical with an apparatus patented by Mr. Tripler 
five years ago. But, while with this apparatus of Prof. Linde's it takes five hours 



USE. 7t3 

to obtain liquid, with Mr. Tripler's apparatus liquid air can be obtained in less 
than an hour from the time of starting. In a subsequent article the writer hopes 
to be able to give data concerning the properties. of liquid air. 

W. H. DICKERSON. 



LIQUID AIR.* 



I 



By Walter H. Dickerson, M. E., '96. 

Through the kindness of Mr. Charles E. Tripler, of New York, the Alumni 
Association was afforded an opportunity at the mid-winter meeting of witnessing 
some experiments with liquid air. It has been the good fortune of the writer to 
have been associated with Mr. Tripler for nearly a year past, and as a member 
of the Alumni Association, it was with pleasure that he came before them as Mr. 
Tripler's representative, and endeavored in the limited time available to give them 
some account as to the production of liquid air, its principal characteristics, and 
some idea of the great possibilities attending its practical application on a com- 
mercial scale. 

A few remarks at this point upon the conditions necessary for reducing 
gases to the liquid state, will probably aid the reader to more clearly understand 
the matter that follows. 

All matter is capable of existing in three states, gaseous, liquid and solid, 
due to its temperature, pressure and volume. If we compress a gas, we increase 
its density, but as long as the temperature is above a certain point, it will not 
liquefy. If, howeyer, we reduce the temperature of a gas to a certain point, it will 
liquefy at a certain pressure and at a less pressure if the temperature is carried 
lower. This temperature, at which a gas begins to liquefy, is known as its 
critical temperature, or point. All gases possess a definite fixed critical tem- 
perature, at or below which they will liquefy, and above which, they cannot be 
liquefied, regardless of the pressure applied. Air at the ordinary temperature, 
has been compressed under fully 4,000 atmospheres of pressure per square inch, 
without liquefying. Oxygen gas, at 17 degrees centigrade compressed by 4,000 
atmospheres per square inch, reaches a density of 1.25, but is still in the form of a 
gas. The following is a table prepared by Prof. Dewar in the London Engineer, 
giving the density of some gases, at the temperature of 15 degrees centigrade, 
and at a pressure of 3,000 atmospheres per square inch : 

per square inch. ^^ ooiling point. 

Oxygen 1. 1034 1. 124 

Nitrogen O.8259 0.885 

Air 0.8820 .94 

Hydrogen 0.0879 

Thus, we see that it is possible to have a gas denser than its liquid. The 
limiting density of hydrogen is 0.12. The existence of "critical temperatures" 
was discovered by Dr. Andrews, of Scotland. All liquids possess, below their 

♦ Reprinted from 7%.? Stevens Indicator. 



714 



USE. 



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USE. 715 

critical temperatures, definite fixed boiling points, for definite fixed pressures. 
In the case of air the boiling point under atmospheric pressure is — 191* Centigrade 
or 312° Fanrenheit. At this point, gaseous air liquefies and remains in the liquid 
state at ordinary atmospheric pressure, so that air can be changed into a liquid 
form by cold alone. A glass of liquid air, exposed to the atmospheric air, will 
receive heat from the warm atmosphere, which will tend to evaporate it, but the 
portion that evaporates, by absorption of heat energy, keeps the remaining liquid 
cool; consequently, a jar of liquid air will take a considerable time to evaporate. 

Mr. Tripler has been engaged in researches in high pressures for the 
liquefying of gases, for a number of years, having spent all his time and a great 
deal of money in this work. During his researches, he devised a simple and 
economical apparatus for the liquefaction of gases. Although Mr. Tripler's name 
has not been before the public until very recently, outside of a limited circle inter- 
ested in his work, his investigations have developed many important results. 

The work of the European scientists, in the practical liquefaction of gases, 
has been chiefly in the following direction: 

Starting with a very easily liquefiable gas, as carbon dioxide, the cold pro- 
duced by the evaporation of its liquid, was used to refrigerate and liquefy a less 
easily liquefiable gas, under high pressure (such as ethylene for example) and 
the evaporation of the liquid ethylene, was in turn used to refrigerate and liquefy 
one of the so-called permanent gases such as oxygen. As the reader can readily 
conceive, it was an elaborate and necessarily expensive plan, as all these gases had 
to be compressed to a high pressure. 

But, with the apparatus devised by Mr. Tripler, all that is necessary to 
produce liquid air is gaseous air, under a pressure from 2,000 to 2,500 pounds pres- 
sure to the square inch. The liquefying apparatus proper consists simply of a 
series of coils of pipe arranged in several concentric cylindrical compartments 
in two large "liquefiers." The coils of pipe, which are capable of withstanding 
high pressures, terminate in a specially designed expansion valve and 
an orifice. The high pressure air entering the liquefier, passes through 
the coils until it reaches the expansion valve and orifice. Here, the 
air is expanded in the expansion chamber to very nearly atmospheric pressure. 
The air in expanding from the high pressure of 2,500 lbs., is reduced in tem- 
perature, and this cold expanded air in passing over the coils from which 
it has just issued reduces the air under high pressure therein contained to so low 

REFERENCES FOR DATA GIVEN IN TABLE 69. 

Lines 2, 4, 7, 9, 10, 11, 12, 13, 15, 16 and 17 are given by Olszewski in 
Philosophical Magazine, February, 1895. 

Lines i, 3, 6 and 8 are given by Prof. Linde in London Engineer, Nov 13, 
1896. 

Line 18 is given by Olszewski in Philosophical Magazine, 1895. Calculated. 

Line 19 is given by Olszewski in Annalen der Physik und Chemie, 1896. 
Calculated. 

Line 5, Critical temperature, given by Ansdell in Proceedings Royal Society, 
Vol, 29, p. 209, 1879. Other data on this line given by P. Villard, Comptcs Rcndus, 
Vol. 120, p. 1262, June 10, 1895. 



7i6 USE. 

a temperature that it is in part liquefied. With this apparatus, liquid can be drawn 
off within fifteen minutes from the time of opening the expansion valve. The 
method of continuously cooling the incoming air by passing the cool expanded 
air back over it, as above described, was discovered by Mr. Tripler, in the winter 
of 1889 and 1890. 

Within the last year or two, certain men in Europe have claimed this appa- 
ratus as original with them, but their claims as inventors of this apparatus are 
easily disposed of by the fact that the apparatus, which they are at present using, 
is almost identical with that which was patented in England by Mr. Tripler over 
five years ago, and also by the fact that the patent examiners have given him a 
priority of three years over all others in the use and application of apparatus 
involving the principles referred to. 

It is a significant fact that, with the apparatus first brought out by these 
claimants, it required 17 hours to produce liquid air, but the time has recently 
been reduced by them to two or three hours. Another significant fact is that these 
same claimants did not bring out their apparatus until after Mr. Tripler had filed 
his applications for patents in England. 

Mr. Tripler was assured a few years ago by certain scientists, that it would 
be impossible to produce liquid air according to his idea. Notwithstanding these 
discouragements, he has by patient persistence, accomplished it, and demonstrated 
that his method was effective. 

The power plant for the production of high pressure air, in Mr. Tripler's 
laboratory, consists of an ordinary tubular boiler, and a three stage straight line 
Norwalk compressor. The principal dimensions of the compressor are as follows : 

Diameter of steam cylinder 16 inches. 



Diameter of piston rod 2 

Stroke of piston 16 " 

Diameter of intake air cylinder io)4 " 

Diameter of piston rod, head end 2^ " 

Diameter of piston rod, crank end ii| " 

Diameter of intermediate cylinder 6| *' 

Diameter of piston rod i^f " 

Diameter of high or 3rd stage air cylinder 2^ ** 

Stroke of all air pistons 16 " 

Steam pressure carried is from 85 to 90 pounds per square inch. 

The cylinders are arranged in tandem, all on the same bed, and are in the 
following order: Steam cylinder, intake air cylinder, intermediate air cylinder 
and high or third stage air cylinder. The steam end is a simple steam engine, with 
adjustable cut-off Meyer valves. 

The air is led to the compressor through a pipe, which extends above the 
roof of the building, in order to get clean air free from dust. Before entering 
the compressor, the air passes through a washer, which washes it free of dust and 
saturates it with water. The air enters the intake cylinder, which is double acting, 
where it is compressed to about 65 lbs. pressure to the square inch. It then passes 
through an inter-cooler, and is reduced to the ordinary atmospheric temperature, 
by means of water circulated through the pipes in' the inter-cooler. It then enters 
the intermediate cylinder, which is single acting, and is compressed to about 400 
pounds pressure. From here, the air is discharged into the second inter-cooler, 



USE. 717 

where it is again cooled by means of the water circulation to the ordinary atmos- 
pheric temperature. It then enters the high pressure or third stage air cylinder, 
where it is compressed to the discharge pressure of from 2,000 to 2,500 pounds 
pressure per square inch. After passing through an after-cooler, to reduce its 
temperature again to that of the atmosphere, the air passes through a separator, 
where all the moisture, oil, dirt, etc., are removed from it, and from there passes 
to the storage tubes. 

From the storage tubes the air under high pressure passes to the liquefying 
apparatus and in from twelve to fifteen minutes from the time of starting, liquid 
air can be drawn off from the apparatus through a discharge pipe at the bottom. 

The present apparatus will produce from two to three gallons of liquid air 
per hour. 

The facility with which the liquid is handled and transported is rather re- 
markable, considering the temperature condition necessary to maintain it in its 
liquid form. It has been transported in three and four gallon quantities to Lynn, 
Mass.; Philadelphia, Baltimore and Washington, with a loss, from evaporation, 
of from 25 to 30 per cent. The receptacle in which the air is carried is nothing 
more or less than a large tin or copper can insulated with about three inches of 
hair felt. 

As noted in Table 69, the critical temperature of air is — 140 degrees Centi- 
grade and the corresponding pressure is 39 atmospheres. The boiling point at 
atmospheric pressure is — 191. 4 degrees Centigrade. Its density is .94. The spe- 
cific heat and latent heat of evaporization of liquid air are unknown. The liquid 
is perfectly transparent and slightly tinged with blue. Both the oxygen and 
nitrogen of air liquefy simultaneously, but do not evaporate in the same relative 
proportions. The nitrogen, having a lower boiling point than the oxygen, evap- 
orates more quickly, so that the liquid after a time becomes substantially liquid 
oxygen. 

There are three methods in measuring these low temperatures — namely, 
the hydrogen thermometer, the thermo-pile or thermo-electric couple, and the 
platinum thermometer. The correct reading of these thermometers all depend 
on the assumption that the laws which govern their actions at ordinary temper- 
atures, hold good at these extremely low temperatures; consequently, the tem- 
perature determinations based on these assumptions can only be taken as approxi- 
mately correct. 

In using the hydrogen thermometer to measure temperature as low as that 
of liquid air, it is open to the criticism that such temperatures approach the crit- 
ical point of hydrogen, and this introduces a great chance of error. In using the 
thermo-pile or thermo-electric couple, it is calibrated at ordinary temperatures, 
and a calibration curve plotted. Assuming that the curve conforms to the same 
laws throughout a wide range of temperature, the curve is exterpolated to cover 
low temperature readings. The instrument readings are taken at the low tem- 
perature and plotted back upon the exterpolated portion of the curve and the 
temperature then determined. The platinum thermometer is probably the most 
reliable of the three, and has been used by most of the European investigators in 
the greater part of their researches in low temperatures. It consists of simply a 
fine pure platinum wire, sometimes bare, and sometimes sealed in a small glass 
bulb, and intended to be placed in the liquid, the temperature of which is to be 



I 



7i8 



USE. 



measured. In using it, its resistance-temperature curve is plotted, a given resist- 
ance corresponding to a definite temperature. The resistance-temperature curve 
of pure platinum, for ordinary and high temperatures, is very nearly a straight 
line, and produced, passes through the origin of co-ordinates, a point correspond- 
ing to zero resistance and zero temperatures. The resistance of the thermometer 
being determined, it is plotted on the curve and the temperature deduced. The 
temperatures thus deduced, depending as they do on an assumption, are always 
expressed as platinum-Centigrade, or platinum Fahrenheit, degrees. When the 
liquid air is dipped up in an ordinary glass tumbler, it boils at first very violently, 
but, after the tumbler has given up its heat and has had its temperature reduced 
to that of the liquid, the liquid air boils gently. 

TABLE 70. 

Specific heats of air calculated by Prof. Linde. Published in London Engineer, 

November 20, 1896. 







PRESSURE IN 


\TMOSPHERES. 






1 


10 


20 


40 


70 


100 


Temperature+100° C 


.2372 
.2375 
.2380 
.2389 
.2424 
.2467 


.2389 
.2419 
.2455 
.2585 
.3105 
.4147 


.2408 
.2465 
.2572 

.2844 
.5048 


.2446 
.2512 

.2785 
.3697 


.2512 

.2773 
.3319 
.8461 


.2583 


0« 


.2986 


_ 50C C 


.4124 


—lOQo C 




— 150° C 




_170o C 









The production of liquid air and oxygen at the Royal Institution of London, 
was a very expensive process, and Prof. Dewar, in searching for a vessel suitable 
for holding the liquid gases and preventing their rapid evaporation, devised the 
vacuum bulb. This consists simply of two bulbs, or vessels of glass, one within the 
other, having an annular space between the walls, and joined in a common neck at 
the top. In this annular space, a very high vacuum is formed, which prevents the 
heat from being conducted from the outer to the inner wall. If the wall of the 
inner bulb or vessel is silvered with mercury, nearly all of the radiant heat will 
be reflected, and the amount of heat that will enter the liquid contained in the 
inner bulb, will be reduced to a minimum. It has been suggested by Mr. Tripler, 
that this bulb, out of courtesy to Prof. Dewar, should be called the Dewar bulb 
or globe. Liquid air when placed in a Dewar bulb, remains in a quiet state, evap- 
orating very slowly, a tumblerful requiring about four or five hours to entirely 
evaporate. If the Dewar globe is unsilvered, the perfect transparency of the liquid 
is shown, as is also its bluish tinge. As the evaporation progresses, the liquid 
becomes richer in oxygen and the bluish color becomes deeper. The change of 
the relative proportions of oxygen and nitrogen in the liquid, due to evaporation, 
and the consequent change in density, is very nicely shown by the following 
experiment : 

If, in a large glass jar or flask, filled nearly full of water, a dipper of liquid 
air is poured, the liquid at first will float on top of the water, because the specific 



USE. 



719 



gravity of pure liquid air is less than that of water. The liquid coming in contact 
with the water, causes rapid evaporation of the air, and in a moment or two, the 
air becoming very rich in oxygen, its density becomes greater than that of water, 
and it dives down into the water in the form of large globules. 

Some idea of the very low temperature of liquid air, may be gathered from 
the experiments showing the ease with which all liquids, having a low freezing 
point, are solidified. 

Both absolute and 95-per cent, alcohol are easily frozen and form a white 
transparent solid. Absolute alcohol solidifies at between — 202° and — 203° Fahr. 
and just before reaching the solid state, becomes very viscous, reminding one of a 
heavy nil. Whiskey is easily solidified, and when frozen, looks like brown sugar. 



f 




FIG. 278. -TUBES EXPI^ODED BY MEANS OF COTTON WASTE SATURATED BY UQUID AIR. 

All the organic liquid reagents and the acids are readily reduced to a solid state 
by means of liquid air. Prof. Dewar has discovered that, if reduced low enough 
in temperature by means of the vacuum pump, liquid air is apparently reduced to a 
solid, but when the solid mass is placed in a strong magnetic field, the oxygen is 
sucked out towards the poles in the form of a liquid, leaving little doubt that the 
apparently solid mass is but a magma of solid nitrogen, containing liquid oxygen. 
Liquid oxygen has never been solidified. 

Some idea of the low temperature that can be obtained by evaporating 
liquid air in a vacuum, is shown by the following experiment: A large test tube 
filled with liquid air is connected at the top with the vacuum pump. When a 
vacuum of about fifteen inches has been reached, the atmospheric air commences 
to liquefy on the exterior of the tube, and trickles from the bottom in a small 
stream. After this condensation has progressed for a few moments, the liquid in 



720 USE 

the interior of the tiil^e is reduced by evaporation to almost pure liquid oxygen, 
and when the vacuum has been raised to 28 or 29 inches, the liquid air on the ex- 
terior of the tube is reduced to a solid state. 

The effects of very low temperatures upon the physical properties of metals 
are very striking, and open up a wide field of investigation for scientists. 

Metallic mercury solidifies at — 39° Fahr. If a proper mould is made, a 
hammer head of mercury can be cast on to a handle by means of liquid air, form- 
ing a hammer with which nails can be driven into boards. Solid mercury when 
hammered is affected very much the same as ordinary lead. It has also been 
found that a bar of solid mercury possesses considerable tensile strength. Pure 
mercury exhibits a fibrous structure, the fibres extending in vertical unbroken lines 
from the bottom of the mould to the top. When amalgamated with a slight per- 
centage of tin, the structure becomes granular. 

Sheet iron and steel, which at ordinary temperatures are pliable, become so 
brittle when reduced to the temperature of liquid air, that they are as easily broken 
as is thin china-ware. Seamless steel tubing, when reduced to this low tempera- 
ture, slivers into long fragments when struck with a hammer. Tin, with slight 
impurities, also become brittle and may be easily broken. 

If the fracture of these metals is examined, it is found to be very granular. 
While the pliability of iron and steel is greatly reduced at low temperatures, the 
tensile strength is greatly increased. Copper, aluminum, pure tin, cadmium, silver, 
platinum and gold, are all apparently unaffected, and are as pliable at the low 
temperatures as at the ordinary temperatures. 

The following table contains some approximate results regarding this sub- 
ject, obtained by Professor Dewar: 

Tension in tons Percentage of ■ 
per sq. inch for elongation for 
a temp, of a temp, of 

15 C. -180C. 15 C. -180 C. 

Copper 22.3 30.0 6.8 13.4 

Iron 34.0 62.7 8.2 4.7 

Brass 25.1 31.4 35.5 32.2 

German Silver 38.3 47.0 10.7 20.4 

Steel 35.4 60.0 29.4 19.5 

The effects on other substances at low temperatures, are as remarkable as 
those upon metals. Resin and paraffin, when frozen in liquid air, are easily re- 
duced to a fine powder, by the pressure of the fingers. Rubber tubing and sheet 
rubber become so brittle, that a light blow will shatter them into fragments. Com- 
mon ice, if placed in the liquid, becomes very granular, and is reduced to small 
fragments by pressure of the hands. Bread, soaked in the liquid, becomes hard, 
and can be crushed like a piece of dry toast. Meat becomes as hard as a stone, 
and has a ring, when struck, like porcelain. An onion, after being frozen in the 
liquid air, shells off in pieces, which, when shaken up in the hand, sound like 
broken china. 

Pictet discovered that chloroform, when treated with liquid air becomes a 
more powerful anaesthetic and also that a patient after being under the influence 
ot chloroform so treated, experiences no bad after-effects upon revivmg, as is the 
case when the ordinary chloroform is used. 



w 



USE. 721 



With liquid air, it is possible to perform some very interesting experiments 
in combustion, as in the liquid, we have oxygen in a very concentrated form. If a 
piece of smouldering wood Is held over a glass of liquid air, that has become richly 
oxygenized by the partial evaporation of the nitrogen, it will burst into a flame 
instantly. A newspaper, soaked in the liquid and ignited, burns vigorously. Hair, 
felt and wool, which will burn only when held directly in a flame, will blaze vio- 
lently, when saturated with the liquid. Cotton waste or cotton batting, treated in 
a similar manner burns with almost explosive violence, and in a manner similar 
to gun-cotton. If the cotton waste is partially saturated with oil and then treated 
as above, the burning is still more violent. In experimenting with cotton waste, a 
small piece which could be easily enclosed in the hand, was soaked in turpentine 
and then saturated ■ with liquid air and placed unconfinedly on the floor, upon 
being ignited it produced a surprisingly heavy detonation, breaking all the glass- 
ware on a table that stood several feet away. Another experiment will serve to 
show 'Still further, the violently explosive nature of this substance when saturated 
with liquid air. About one-half ounce of cotton waste saturated with oil and with 
liquid air, was placed in the end of a ^-inch wrought iron pipe which was 20 
inches long, and open at both ends. On igniting the cotton waste a violent explo- 
sion took place, bursting and curling the heavy pipe as if it were so much paper, 
for a distance of ten inches. 

Steel and iron may also be burned in the richly oxygenized liquid. The 
following experiment will afford a striking illustration : If a steel writing pen be 
securely fastened to a match, and the match ignited and then held over the liquid 
air, it will burn so intensely that the pen will also become ignited and burn vio- 
lently with a beautiful scintillation, throwing off globules of the molten metal 
which, as they fall, will be fused into the glass vessel containing the liquid. If an 
ordinary electric light carbon is heated on the end with a blow-pipe until it glows, 
and then immersed in the liquid, it will burn and be consumed very much as the 
carbon in the arc lamp, giving out a brilliant light and generating a large quan- 
tity of ozone. By means of liquid air, steel may be fused into ice ; this is shown 
by the following beautiful experiment : 

A glass beaker is partially filled with liquid air, and immersed in a vessel of 
water ; in a few minutes, a thick coating of Ice is formed on the exterior. If the 
glass beaker is then emptied of the liquid, and warmed by pouring water in it, the 
coating of ice can be slipped off and you have an ice-tumbler. Filling this partially 
full of liquid air, and burning a thin strip of steel, as in a former experiment, the 
steel will be fused into the walls of the ice-tumbler in the same manner as it was 
fused into the glass. 

The expansive properties of liquid air are very nicely illustrated by the three 
following experiments : Fill a large test tube with the liquid, and close up the end 
with a cork, through which projects a long glass tube. A very small amount of 
heat, even the heat of the hand will drive the liquid up through the tube, to a con- 
siderable height in the air, giving a good illustration of a geyser. If a heavy piece 
of copper pipe, closed at one end, Is clamped In a vise, and two or three spoonfuls 
of liquid air poured in, and a wooden plug is driven tightly in the open end, the 
expansion of the air from the liquid to the gaseous state, will almost instantly 
force the plug from the pipe, with a loud report. 



722 USE. 

An ordinary tea kettle, filled with liquid air, boils in the same manner in the 
atmosphere, as though it were filled with water and placed over a hot fire; placing 
on a hot stove increases the ebullition very slightly, but pour a tumbler of cold 
water in it, and it boils furiously, and the water in a few minutes will be reduced 
to ice. This experiment has suggested itself as being the 20th Century revision of 
"Watt and his Tea Kettle" in an open fireplace. 

The property of certain bodies to phosphoresce and the cause of phosphor- 
escence, is a subject about which very little is known. Liquid air enables us to 
gain some information regarding this subject. Such substances as ivory, celluloid, 
kid leather, feathers, blotting paper, etc., will not phosphoresce at ordinary temper- 
atures, but upon being immersed m liquid air, and reduced to its low temperature, 
and then exposed to a strong calcium, or arc light, will phosphoresce in a beautiful 
manner, as long as they remain at the low temperature. Tungstate of calcium, 
which is used for coating the fluorescent screens in the fluorescope, when reduced 
to temperature of liquid air, loses its fluorescent property entirely. A set of phos- 
phorescing tubes, such as are used in physical laboratories to show phosphor- 
escence, lose their phosphorescent properties entirely when reduced to the temper- 
ature of liquid air. A vacuum, or "Dewar" bulb, filled with filtered liquid air, can, 
in connection with the electric lantern, be used as a lens to focus the heat rays 
and with this lens paper may be burned. 

Another series of very interesting experiments, are those which show the 
destruction of chemical aflSnity at low temperatures. Metallic sodium combines 
instantly with water at ordinary temperatures, but if the metal is first cooled in 
liquid air, and then thrown on the water, it will float for several seconds until 
v/armed up before combining. Nitric acid and metallic sodium may also be mixed 
at the temperature of liquid air without combining. A battery consisting of sodium 
and carbon with a concentrated caustic soda solution between them, was placed 
ill liquid oxygen. The spot of light on the scale of the galvanometer, to which the 
battery was attached, came to rest at zero, showing that there was no chemical 
action taking place between the elements of the couple. Liquid oxygen has been 
reduced to such a low temperature by evaporating under the vacuum pump that a 
splinter of wood, with a glowing spark on the end, will not burst into a flame when 
immersed in the liquid. The above experiments in the destruction of chemical 
affinity, with the exception of sodium and water, were all performed by Prof. 
Dewar. 

Atmospheric air is a very good electric insulator, and in the liquid state is 
pioportionately more so. The same amount of energy will produce a spark in 
liquid air of only one-sixth the length that would be produced in the atmos- 
phere. 

With liquid air in connection with a strong electro-magnet the magnetic 
properties of liquid oxygen can be shown. If the pole pieces are brought com- 
paratively close together and liquid air poured over them, the liquid nitrogen 
will run off, while the liquid oxygen will cling to and form a bridge between the 
poles. An electric conductor, when at a low temperature, will offer less resist- 
ance to the passage of electric current than when at a high temperature. Pro- 
fessor Dewar has found that with pure metal conductors the resistance varies 
ahnost directly as the temperature. But with conductors made of alloys the re- 



r 



USE. 723 



sistance is very little affected by a reduction in temperatures. It was also found 
that the strength of a magnet was much increased when reduced in temperature. 

Another interesting electric fact is that when liquid air is poured into a 
warm metal can, the can becomes charged, acting like a Ley den jar, and from 
which a good-sized spark can be drawn. 

In the foregoing matter the production of liquid air has been briefly out- 
lined, and some experiments described which show its characteristics. 

As an agent in scientific research it opens up a wide field of investigation. 
In this direction valuable data has been obtained by the European investigators. 
Profs. Dewar and Fleming, in particular, have obtained a large amount of data 
relating to the physical properties of matter at low temperatures, and especially 
the electrical properties. 

As a refrigerant, liquid air is almost perfect, being pure, clean and harm- 
less ; from it any desired temperature may be obtained. 

For motive power purposes it offers a very desirable agent, the amount of 
power obtained being governed by the amount of atmospheric heat admitted to it. 

While possessing no power in itself, except as heat is applied, yet, when 
mixed with certain substances, an explosive is formed, which has been said by 
one of the most eminent authorities on high explosives to be more powerful than 
dynamite or gun-cotton. 

Results of much importance may be looked for from the application of 
liquid air in the practical electrical field, because of its properties of lowering the 
resistance of a conductor, and increasing magnetic strength of a magnet, and 
also because of its perfect insulating qualities. 

The Pictet chloroform experiment offers a suggestion of what may be ex- 
pected from its application in industrial chemical work. 

In concluding this article no more fitting sentiments could be expressed 
than those uttered by Mr. Tr-ipler during a recent demonstration of this sub- 
ject. 

"Can it be possible that a power so manifest, fully a hundred times more 
powerful than that of steam, shall lie dormant, as steam did for centuries, without 
an effort to utilize it? 

"Shall we allow the rays of the sun to pass by us without an effort to 
utilize them, when we have here shown a manifestation of power from those rays, 
more abundant than Watt had with his tea kettle boiling on the fire? 

"It has been my privilege to bring this problem one step further toward its 
ultimate success, and I can now see clearly its solution. It requires only the me- 
chanical appliances to place in the hands of the present generation the greatest 
force of the age." 



St. Paul, Minn., Jan. 16, 1899. 
Editor Compressed Air : 

On page 713 of this cyclopaedia on "Liquid Air," reference is made to Prof. 
Dewar's table of the density of some gases at a temperature of 15" Centigrade, 
and at a pressure of 3,000 atmospheres per square inch. 

Will you please have the kindness to explain how these very high pressures 
are obtained, and what materials are used for this purpose? 



724 USE. 

Thanking you in advance for your information, and always thankful for the 
useful information to be found in your CoMrRESSED Air. Frederick Thede. 

Such pressures as 3,000 atmospheres pressure per square inch could be 
obtained by multiple or stage compression, just the same as 3,000 lbs. per square 
inch is obtained, only the compressor would need to be of special construction to 
suit that high pressure. Or it could be obtained by compressing the gas, say to 
5,000 lbs. pressure per square inch, and then connect the storage tube or flask to 
hydraulic pump and piunp in water until the gas had been compressed to required 
pressure. Either steel or bronze tubes or flasks made the proper thickness of wall 
to withstand such pressures would answer perfectly well. Care should be taken, 
though, that the metal is of dense enough grain to prevent escape of gas through 
metal itself. 



LIQUID AIR. 

We have been asked from time to time to express our opinion on liquid air, 
its usefulness, its commercial value, and whether or not we recommend persons 
taking stock in the several liquid air companies which have been organized. The 
province of this paper has been to publish in its columns descriptions of liquid air 
generating apparatus and various interesting experiments made with this extraor- 
dinary substance. We have also published opinions, ideas and theories on the sub- 
ject, because we believe that liquid air being now an accomplished fact should be 
understood and the various ideas and suggestions agitated so that out of so many 
things we may be directed to something practical. Thus far we simply know that 
liquid air may be produced in large quantities by an air compressor and an expan- 
sion installation, and that the cost of producing it has been considerably reduced 
during the past year or two. When produced its properties establish its identity, 
and through its extremely low temperature we have been able to perform certain 
interesting experiments, which are in some cases valuable, from a scientific point 
of view ; but it does not follow that liquid air is going to do what its promoters 
have proclaimed. 

We are by no means sure that it is going to make money in the present 
generation, and yet we would not be surprised to learn that some one has found 
a practical application in its use. Such application, in fact, as may yet give it a 
commercial value. 

Things that are new and of great value to mankind are slow in reaching 
practical results. A period of 75 years elapsed after the discovery of the electric 
arc before electric lighting reached a point when it became commercially valuable. 
Magneto electricity was brought to a point of great interest in science, and yet 
it was not until 50 years afterwards that dynamos and electric motors were used. 
The industry of refrigeration is now a large one, made commercially useful be- 
cause of the liquefaction of ammonia gas, and yet ice was first made artificially 
in 185 1 at Apalachicola, Florida, by Dr. Gorrie, and by means of compressed air. 

We may say at present that liquid air is simply a substance of great 
scientific interest, yet it would be quite unwise to prophesy what the future may or 
may not bring forth. This very uncertainty has unfortunately been worked upon 






USE. 725 

by promoters of schemes to sell stock. The fact that some remarkable results are 
being accomplished with this substance and its great novelty, are used for building 
up an easy foundation for the smart promoter who has issued stock and sold it 
on nothing but possibilities. The promoter is always attracted to things theatrical, 
and wins greater success in such a field than on lines of common, safe business 
practices. It is simply necessary to make a demonstration of liquid air, and pre- 
pare some wonderful experiments to make it pay, because the public is not 
scientific or technical and falls readily into surprise and error in the great possi- 
bility of a thing, which is so new and mysterious. It is a "get rich quick crowd" 
which falls into such a trap as this, and we are glad to say that in our judgment 
such schemes can only flourish in a short period of time. The reaction will 
surely come, and liquid air will remain as it is, simply a scientific experiment of 
great interest and value. Over all this there is a possibility of some good coming 
out of it. There are so many men at work upon it seeking to grind something 
out of it, that it is but natural to expect results 'if it be within the limits of 
possibility. 



THE LIQUEFACTION OF AIR. 



ITS COMMSRCIAL VALUE. 

An interesting demonstration of the liquefaction of air was given in 
University College, Dundee, Scotland, recently. The proceedings took place in the 
chemistry lecture room, and there was a large attendance of members of the 
society and friends. Professor Waymouth Reid, who presided, said it was a tradi- 
tion of the society that as soon as any important scientific discovery was made it 
was practically demonstrated to the public of Dundee. In conformity with this 
time-honored practice this lecture had been arranged to show how air could be 
reduced to a liquid form. Professor Kuenen would give the necessary explana- 
tions. Unfortunately the college could not supply him with the apparatus, but 
they had been able to secure the services of Mr. W. Hampson, London, one of 
the experts of the Brins Oxygen Company, who had brought the apparatus he had 
himself invented to Dundee. The apparatus to be used had been made for Dr. W. 
R. Lang, of Glasgow University, who was also present, and who had kindly con- 
sented to it being employed that evening. (Applause.) 

AN INTERESTING IMAGINATION. 

Professor Kuenen said the subject of liquid air had been brought promi- 
nently before the public of late, chiefly in connection with magazine articles, 
originating largely from a country which, among its qualifications, was celeb>rated 
for an enterprising imagination that scorned to be hampered even by truth or by 
probability. (Laughter.) Apart from the attractiveness of the subject of the 
lecture, he was supported by the chairman, who with his usual generosity had 
offered himself as an object of experiment without imposing any limiting condi- 
tions. (Laughter.) That afternoon he offered to drink liquid air, but he would 
not be asked to do that . (Laughter.) He was also supported by Mr. Hampson, 
whose ingenuity as an inventor was equal to his skill as a demonstrator. (Ap- 



726 ■ USE. 

plause.) While Mr. Hampson was preparing his apparatus, he (the Professor) 
would make a few remarks on the principle on which the production of liquid air 
was carried out. If a quantity of air at an ordinary temperature was compressed 
into about 800 times as small a volume there would be produced a very dense gas, 
so dense that it would resemble ordinary liquid in regard to the way in which it 
acted on light — it would refract light as a liquid; and it would be acted on by 
electric and magnetic forces in the same way. At the same time it would not be 
liquid air, because they would not have that condition in which the lighter portion 
was separated from the heavier portion by means of a liquid surface. If carbon 
dioxide was pressed into a cylinder it separated into two layers — there was a liquid 
and a vapor part. It was more than a century ago since the first gas — ammonia — 
was liquefied in that way, and in the course of this century — he meant the nine- 
teenth century — (laughter) — all the other known gases had been liquefied, and 
two important facts had been discovered in the process — first, that the lower the 
temperature the more easy wmild the gas be liquefied by compression, and, second, 
that gases which resisted liquefaction by pressure might be liquefied by a suffi- 
cient lowering of the temperature. Carbon dioxide at 20 degrees C. required a 
pressure equal to 50 atmospheres to liquefy it ; but if the temperature was reduced 
to freezing point (32 degrees Fahr.) it would only require 35 atmospheres to 
liquefy it. There were seven gases — called the permanent gases — which could 
not be liquefied by compression, but they cculd be liquefied by reducing the temper- 
ature. The temperature which they must get below before gases could be lique- 
fied was called the critical temperature. Air could be liquefied if the temperature 
was reduced below 220 degrees Fahr. The boiling point of a substance was the 
temperature at which one atmosphere was sufficient pressure to keep the substance 
in a liquid state in an open vessel, and the boiling point of air was — 314 Fahr., or 
346 degrees below ordinary freezing joint. The next question was — How to 
reduce the temperature of air to that low degree? It could either be done by 
cooling it from the outside or by making it cool itself. People thought that by 
taking exercise or doing work they could get warm, but it had been shown that 
heating was only a secondary effect of doing work, and they could make the gas 
cool itself by making it work. It had been shown by Joule and Lord Kelvin that 
when air was allowed to fall from a high to a low pressure it cooled itself. But 
that would not be sufficient to bring it down to — 192 degrees C, which was the 
boiling point of air, and Mr. Hampson had combined that principle with the prin- 
ciple of cooling by expansion. The general working of the system was that the 
air was first compressed into a cylinder at 150 atmospheres, and by means of a 
copper tube it passed into an exhaust cylinder, in which by expansion it cooled 
40 or 50 degrees. In the exhaust cylinder there were over 100 yards of stout cop- 
per tubing, through which the compressed air passed, and as it flowed into the 
cylinder and expanded -and cooled the temperature got lower and lower by the suc- 
cessive action of each quantity of incoming compressed air, till it reached — 192 
degrees C, when the air passed into a liquid form. It was then drawn off from 
the apparatus by means of a Dewar vacuum tube and placed in an open vessel for 
experimental purposes. The nitrogen in the air was more difficult to liquef^han 
the oxygen, and by exposure to the ordinary air the nitrogen returned more 
rapidly to its original state than the oxygen ; so that after a short time the liquid 
was almost wholly pure oxygen. The liquid air now produced was the first that 



f 



USE. 727 

had ever been seen in Scotland, and they might be proud that it had been first 
produced in Dundee. (Applause.) As matter of fact, there had never before been 
such intense cold in Scotland, even in the glacial period. (Laughter.) 

Mr. Hampson then carried out a number of experiments by means of the 
liquid air, such as have beeen referred to frequently in this journal. 



LATENT HEAT OF EVAPORATION OF LIQUID AIR. 



k 



BY WALTER H. DICKERSON, M. E.^ '96. 

During May, 1898, the writer, in connection with Professor D. S. Jacobus,* 
made some determination of the latent heat of evaporation of liquid air at the 
Stevens Institute of Technology. 

As a result of the investigation the latent heat of evaporation at atmos- 
pheric pressure was found to be 123.0 British thermal units per pound 

The method of determination was as follows : 
. A large mercury mirror Dewar vacuum bulb was employed to contain the 
liquid air. The vacuum bulb consisted simply of two glass bulbs, one within the 
other, and joined in a short neck. 

These bulbs have, between the walls, an annular space of about one-half 
inch, which is exhausted to a very high vacuum. If a drop of metallic mercury 
is originally introduced into this vacuum space, it will be changed into vapor 
when the vacuum is formed. On filling the inner bulb with liquid air, the mer- 
cury vapor in the vacuum space will be condensed on the surface of the inner 
bulb and a mercury mirror formed. The vacuum space prevents ingress of heat 
to the liquid air by direct convection and the mercury mirror intercepts the radiant 
heat so that the rate of evaporation in this form of containing vessel is very 
low. 

The vacuum bulb was filled with liquid air and weighed, and the rate of 
constant evaporation due to the heat of the atmosphere determined. A small bar 
of metal of known weight and temperature was then introduced into the liquid 
air and after it had acquired the temperature of the liquid, it was withdrawn and 
the bulb weighed again, the length of time the metal bar was in the liquid air 
being noted. Then, knowing the initial and final temperatures, specific heat, and 
weight of metal bar, and also the weight of the liquid air evaporated, the latent 
heat of evaporation of the liquid air could be calculated. 

No means were at hand to determine the temperature of the liquid air and it 
was therefore taken as the boiling point at atmospheric pressure and temperature, 
given by Prof. Dewar and others as — 312° F., or — 181.4° C. Although the 
liquid air used was slightly richer in oxygen than the ordinary atmospheric air, 
the error due to the difference of temperature from this cause was considered 
well within the error of other observations and was therefore disregarded. 

There were three determinations made, with a different metal in each 
instance. The three metals used were iron, copper and aluminum, each in the 

* It is very generous of Mr. Dickereon to mention my name as I di<l not assist him, except in 
placing apparatus at his disposal.— D. S. J. 



728 



USE. 



form of a small cylindrical bar. The specific heats of these particular bars had 
previously been determined for a range of temperature from the atmosphere to the 
boiling point of liquid air with the following results : 



TABLE 71. 



Metal. 


Weight of Bar 
in grammes. 


Specific Heats. 


Iron 


51.925 

63.49 
19.865 


.0914 for range of temperature of from + IH^ C. to— 

181.4° C; 
.1162 for above + 13^^ C. 
.0868 from + 11° C. to-181.4° C. 
.094 for above + 11° C. 
.1833 from -f 14.5° C. to— 181.4° C. 
.2173 for above + 14.5° C. 


Copper 

Aluminum 



During the tests the following observations were noted: 

FIRST EXPERIMENT WITH IRON BAR. 

Temperature of atmosphere, 23.9° C. 

Temperature of iron bar, 23.6° C. 

Total weight of vacuum bulb and liquid air before immersing iron bar, 338 
grammes. 

Total weight after iron bar had acquired temperature of liquid air and been 
withdrawn, 319 grammes. 

Time between weighing, 10.5 seconds. 

Rate of constant evaporation per minute due to heat of atmosphere, .4286 
grammes. 

Total constant evaporation, 4.500 grammes. 

Net evaporation due to iron bar, 14.5 grammes. 

Heat units in iron per gramme. 

+ 13° C. to — 181.4° C. = 17.768 
+ 23.6° C. to + 13° C. = 1.232 



986.57. 



Total heat units per gramme 19.000 

Total heat units in iron bar in grammes-calories, + 23.6° to 

Latent heat, by iron bar, 68.03 calories. 

SECOND EXPERIMENT WITH COPPER BAR. 



181.4*' = 



Temperature of copper bar, before immersing, 23.2" C. 

Weight of bar, 63.49 grammes. 

Weight of vacuum bulb and liquid air before immersing copper bar, 312 
grammes. 

Weight of vacuum bulb after bar had acquired temperature of liquid air 
and been withdrawn, 291 grammes. 



f 



USE. 729 



Time between weighings, 10.92 minutes. 

Rate of constant evaporation per minute due to heat of atmosphere, .4342 
grammes. 

Total constant evaporation, 4.741 grammes. 

Total evaporation, 21 grammes. 

Net evaporation due to copper bar (21 — 4-741 )> 16.26 grammes. 

Heat units in one gramme copper, 

+ 11° C. to — 181.4° C. = 16.70 
+ 23.2° C. to + II" C. = 1.15 



Total, + 23.2" C. to — 181.4° C 17.85 

Total heat of copper bar in gramme-calories, 1126.948. 
Latent heat of evaporation of liquid air by means of copper bar, 69.31 
calories. 

THIRD EXPERIMENT WIITH ALUMINUM BAR. 

Temperature of aluminum bar before immersing, 23° C. 

Weight of bar, 19.865 grammes. 

Weight of vacuum bulb and liquid air before immersing aluminum bar, 
284 grammes. 

Weight of vacuum bulb after bar had acquired temperature of liquid air and 
been withdrawn, 269 grammes. 

Time between weighings, 9.4165 minutes. 

Rate per minute of constant evoporation due to heat of atmosphere, .4166 
grammes. 

Total constant evaporation, 3.9229 grammes. 

Total evaporation, 15 grammes. 

Net evaporation due to heat of aluminum bar, 11.077 grammes. 

Heat units per gramme of aluminum, 

+ 14.5° C. to — 181.4° C. = 35-908 
+ 23.° C. to + 14.5° C. = 1.847 



Total 37.755 

Total heat in aluminum bar used, 750.1 calories. 

Latent heat by aluminum bar, 67.72 calories. 

Average latent heat by iron, copper and aluminum bars, 68.35 calories'. 

Latent heat expressed in B. T. U. per pound, 123.03. 

The writer wishes to express his thanks to Mr. Chas. E. Tripler for so 
kindly furnishing the liquid air with which to make the investigation; also to 
Prof. Trowbridge, Columbia University, for loaning the metal bars and furnish- 
ing the data of the respective specific hedits. —St evens Institute Indicator. 



Ottawa, Canada, Dec. 13, 1899. 
Editor Compressed Air: 

Permit me to point out one or two circumstances in connection with Mr. 
Dickerson's method, set forth in his article in the current number of your inter- 



730 USE. 

esting periodical, for measuring the latent heat of liquid air, which seems to me to 
depart further than should be permitted from accurate measurement. 

Mr. Dickerson mentions that the liquid experimented on contained a greater 
proportion of oxygen than does air and that he nevertheless disregarded the higher 
boiling point which this circumstance would naturally involve in view of its com- 
parative negligibility. He was undoubtedly justified in doing so as, unless the 
oxygen was very much out of proportion, the rise in temperature could not be 
more than about a single Celsius degree. I must point out, however, that, 
although he states the boiling point of liquid air correctly in terms of Fahrenheit 
degrees as — 312 degrees, he has taken the temperature of boiling oxygen instead 
of that for boiling air when stating the thing in Celsius degrees. That is to say, 
he has taken — 181.4 degrees C. instead of — 191.4 degrees. This is an error to 
start with of no less than 18 degrees F. His results are stated in Fahrenheit 
units. If he had worked from the Fahrenheit temperature, which he took cor- 
rectly, he would have been all right but, instead, he used the French units and 
then worked them back into English. 

This error, however, while regrettable and one which vitiates his results 
clear through, can readily be corrected for and the experiment recalculated without 
repeating any of the work. The chief points which I wish to criticise are funda- 
mental in the method. 

What occurred when the metal pieces were immersed in the liquid air was 
not at all a boiling off of air, but of an atmosphere containing but a few per cent, 
of oxygen, and the heat rendered latent by this occurrence was the sum of the 
latent heat absorbed by the two constituents, which was quite different ,f ram the 
latent heat of the same weight of air. One might as well endeavor to estimate the 
latent heat of a mixture of water and alcohol by a method which caused a 
volatilization only of a fraction of the whole mass and which, in consequence, 
caused a vaporation of the alcohol out of all proportion to the ratio of its presence 
in the original mixture. 

This serious error would throw out the result or not depending on whether 
or not the latent heat of nitrogen deviates much from that of oxygen. I am not 
aware whether it does so or not, but, as Dewar's figure for the latent of oxygen is 
144 B. T. U., and as Mr. Dickerson's, when corrected for the error above pointed 
out in connection with the boiling point of air, becomes, for the latent heat of a 
mixture of oxygen and nitrogen of indeterminate composition, 129 B. T. U., it 
will be obvious that there is a probability of a pretty considerable divergence. 

Of course, what he should have done was to arrange a method in which 
the whole of the liquid would be evaporated or else to measure the amount of 
heat rendered latent in evaporating any weight of a mixture which could thereafter 
be analyzed and working the result by algebra against another result from the 
gasification of a mixture of oxygen and nitrogen of widely different (and known) 
compositien. Respectfully yours, 

Ernest A. Le Sueur. 



USE. 731 

ON THE SEPARATION OF THE CONSTITUENT GASES OF LIQUID 

AIR— DISTILLATION OF THE GASES— WORK OF 

COMPRESSION— COST OF POWER.* 



BY PROF. RAOUL PICTET AND MORITZ BURGER. 

It will be our effort in this paper to impress our hearers with the true value 
of the process by which liquid air has been produced. To make the subject clear, 
we will give a brief description of the process and the original primitive appa- 
ratus. 

The present process for liquefying air in quantity and at low cost presents 
many valuable features for consideration, and is the one along the lines of which 
past efforts have been principally directed. 

It consists, in brief, of compression of the air, cooling after compression 
by water coolers, and expansion of this compressed and cooled air in a counter- 
current, or self-intensifying, apparatus, wherein the cold expanded air flows back 
over the incoming stream of compressed air and serves to refrigerate or intensify 
itself down to the critical temperature of liquefaction. 

All previous apparatus constructed upon this principle have lacked in one 
essential feature, namely, insulation against atmospheric heat. The importance 
of this feature does not seem to have been appreciated, as it has been customary 
to coil up the tubes forming the apparatus in any convenient or compact form, 
without regard to protection of the point of critical temperature. 

Obviously, when we are dealing with great extremes of temperature, 
insulation becomes of vital importance, viewed from the point of efficiency or 
economy. In past practice this lack of insulation has been overcome by the 
application of increased refrigeration, secured by greater expenditure of power, 
resulting, in all instances, in excessive cost of production of the necessary low 
temperature for the liquefaction of air. 

In this primitive condition the art languished, until it was conceived that 
the point of critical temperature could effectually be protected, or insulated, from 
atmospheric heat by its isolation within the surrounding coils, and by the out- 
running refrigerating streams of cold expanded air, whereby the radiant atmos- 
pheric heat would be intercepted and carried outward. 

The direct or immediate application commercially of this new process of 
producing low temperatures lies in its value for the separation of the several gases 
or components of atmospheric air and making them available commercially. 

First, it is necessary to consider the laws of nature, which dominate all 
gases and vapors. The exactness and value of these laws are comparable with 
those of astronomy. In our case, we simply apply them to atmospheric air. All 
vapors, compressed at a certain temperature, rise in pressure to a certain limit, 
which cannot be exceeded. This limit represents the maximum tension of the 
vapor. Beyond this limit any change of volume is accompanied by a condensa- 
tion of the vapors or an evaporation of the gas previously condensed. 

The phenomenon of the transformation of the nature of two mixed and 
compressed gases shows a special character if the liquid obtained out of every 



* From addreps delivered before Franklin Institute. 



732 USE. 1 

one of the gases dissolves itself in the liquid obtained from the other. The 
main character of this transformation is the following: 

It can be said that, in a liquid which represents a solution of two soluble 
liquids which can be mixed in all proportions, the liquids and the vapors derived 
from them will never, at any temperature, show the same proportion of weight 
of their constituents. Always, and without exception, the more volatile con- 
stituents of the liquid mixture will create a vapor richer in weight than that of 
the corresponding constituents, whatever may be their proportions in the liquid 
which produces the vapors. Thus we obtain out of a liquid mixture composed 
of 10 per cent, alcohol and 90 per cent, water, at a temperature of 32° F., vapors 
which contain 64 per cent, of alcohol and 36 per cent, of water in weight. This 
law is the basis of all processes of distillation and refining of mixed liquids. 

It is entirely applicable to liquid oxygen and nitrogen. Both gases become 
vapors when being cooled to a temperature of 292° F. below zero, but the tem- 
perature of liquefaction of one of the gases, the oxygen, under atmospheric pres- 
sure lies 25'' above the temperature of evaporation of the nitrogen at the same 
pressure. These two liquids dissolve in any proportion. It may be remembered 
that the latent heat of evaporation decreases with an increase of the temperature. 
According to this, liquid air evaporates at a temperature of 317° F. below zero, 
whereby one pound of liquid air will absorb about 325 B. T. U., while at a tem- 
perature of 292° F. below zero, it only absorbs about 305 B. T. U. This reduc- 
tion allows us to explain, without difficulty, the theory of our process, consisting 
in the separation of oxygen and nitrogen. 

LIQUEFACTION OF AIR. 

The atmospheric air consists mainly of four constituents, only three of 
which have industrial value. The atmospheric air is composed, at a temperature 
of 60" F., of nitrogen, 79 to 80 per cent, in volume ; oxygen, 21 to 20 per cent, in 
volume; carbonic acid, from 3 to 50 per 10,000; and watery vapor, about 29 per 
1,000 in volume. The problem of the separation consists of the following parts : 

First — Perfect extraction of the watery vapors before further operation. 
The same would offer many obstacles to the successful operation by its liquefac- 
tion and its freezing. 

Second — Extraction of the carbonic acid, which freezes in form of white 
snow at a low temperature of the gases. 

Third — Liquefaction of the snow purifies quantity of air. 

Fourth. — Distillation and refining the liquid atmospheric air, collecting the 
oxygen and the nitrogen in different separate gas holders. 

Here is may be mentioned with special emphasis that there exists a funda- 
mental difference between distilling, in our sense of the word, and the general 
conception of that term. If we distill alcohol, in industry, we introduce it in a 
liquid form into the apparatus, and after the process we regain it again in liquid 
form, in which state it is used for commercial purposes. During the process we 
introduce heat, thereby converting the liquid to vapors, which are afterward 
liquefied by condensation. 

In our process it is the exact reverse. We take air in a gaseous state and 
reduce it to a liquid and again evaporate it, in the form of separated constituents, 
into different gas holders, from where they may be taken for the numerous indus- 



pw'f 



USE. 733 



trial applications. During the process we cool the gases instead of heating them. 
This is, so to say, a reversed distillation, but the functions follow the same laws. 

The atmospheric air enters first a filter wherein all dust or foreign matter 
is removed. This filter purifies the air and delivers it to the compressor, which 
can be driven by any available source of power. The compressed air then enters 
a cooler under a pressure of from thirty to 150 pounds per square inch. There it 
is cooled to about 40° F. below zero. This cooler contains a solution of calcium 
chloride, which condenses the entire amount of moisture out of th^ air. After 
leaving this cooler, the compressed air enters the heat interchanger. This is a 
very important part of the system. In the interchanger the compressed air is 
cooled to the temperature of the liquid air by interchanging the temperature of the 
cold gases of evaporation with the temperature of the incoming stream of new 
air. The heat interchanger consists of three divisions. It is a tubular appa- 
ratus, in which a counter-current of the gases is produced. In the first part, the 
cold nitrogen, arriving from the separator, flows through a system of parallel 
tubes, on the outside of which compressed air circulates. In the second part, 
the nitrogen of the first series is replaced by a mixture of oxygen and nitrogen, 
which does the cooling of the compressed gases in this part.. Finally, in the 
third part, we have pure or industrial oxygen in the tubes, for interchanging the 
heat. 

The quantity of the separated gases coming from the separator is in weight 
equal to the quantity of the mixed and compressed gases before entering the 
separator. By giving the heat interchanger enough cooling area a perfect inter- 
change of heat can be secured, provided the losses through radiation and con- 
duction of heat are a minimum. 

SEPARATING THE GASES. 

The compressed and cooled gases enter the separator at a temperature of 
about 310" below zero. This apparatus consists of a series of parallel and hori- 
zontal trays. Each tray is provided with a flat spiral coil. All these coils are 
connected between one another, and form, thus, an enormous coil, starting at the 
top and ending at the bottom of the apparatus. 

The liquefier or separator can have any number of these trays — ten, fifteen, 
twenty, or even more, if a great purity of the separated gases is required. Each 
tray of the apparatus is connected with the next lower one by means of an 
overflow. All trays are filled with liquid air. The compressed and cooled air 
in the tubes lying on the trays, and bathed in liquid air, will liquefy. This liquid 
air has a milky appearance, ai it contama carbonic acid in the solid state. We 
purify it with filters located at the top of the apparatus. This liquid, as it emerges 
from the liquefying coil, is purified by filtration, on its way to the trays of the 
separator. The filtered liquid air then falls by its own weight from the top 
downward, from tray to tray, to the bottom of the apparatus. 

During the passage of the liquid air from the top to the bottom, the entire 
separation of its constituents, oxygen and nitrogen, is effected. At the same time 
the necessary supply of liquid air for maintaining the process is continually re- 
placed, and even increased, by an additional amount of work. In effect, the com- 
pressed atmospheric air liquefies in the coil under a pressure of from thirty to 



734 USE. 

150 pounds per square inch, at a perceptibly higher temperature than that of the 
liquid air which surrounds the coil, and which boils under atmospheric pressure. 

As formerly explained, the latent heat of evaporation of the liquid air is 
smaller under higher pressure than under atmospheric pressure. The higher, 
therefore, the pressure in the coils, the greater will be the amount of air liquefied, 
with a correspondingly great amount of liquid air evaporating on the outside, 
under atmospheric pressure. Under all conditions, the amounts liquefied and the 
amount evaporated will at least be equal. The constant precipitation of liquid air 
from the coil into the upper part of the apparatus maintains a continuous supply 
upon all the trays, equaling the already evaporated quantity of liquid air. The 
process is automatically regulated by the pressure. 

The gases evaporated on the first upper tray will be pure nitrogen, because 
the nitrogen is a great deal more volatile than the oxygen, and the ratio of its 
weight to that of oxygen is as four is to one. It may be interesting to note that 
the nitrogen evaporating on the upper trays of the separator has a purity of from 
99 to 99J^ per cent. In order to collect this gas, it suffices to connect the upper 
trays with the heat interchanger, and to lead the nitrogen gas from there to the 
gas holder. 

If the amount of the evaporated nitrogen is great enough to diminish the 
ratio of the gases in the remaining liquid, the proportion of oxygen to nitrogen 
will be such that the gases evaporated on the next lower trays will begin to show 
some traces of oxygen. 

In the central trays, and especially nearer to the bottom, the evaporated 
gases will become richer in oxygen. If four-fifths of the original liquid air is 
evaporated, the remaining oxygen will have a purity of 85 per cent. If nine- 
tenths of the original liquid air is evaporated, the oxygen evaporating from the 
last trays will be of 90 per cent, purity. The last twentieth of the original liquid 
can be considered to be chemically pure oxygen, and may be applied to all pur- 
poses to which chemically pure oxygen, hitherto produced in laboratories only, 
is applicable. 

It is obvious that the gases, which, after leaving the separator represent a 
mixture of oxygen and nitrogen, not applicable industrially, have to be led to the 
heat interchanger, in order to give up the quantity of energy represented by their 
low temperature, from whence they may be allowed to escape. However, as soon 
as the gases evaporating from the last trays are rich enough in oxygen, they will 
be collected in the gas holder, from where they may be distributed for general use. 

It is possible to manufacture this gas in two different qualities, namely, 
industrial oxygen and pure oxygen. Pure oxygen will always be derived from 
the final evaporation of the last twentieth of the total liquid. Industrial oxygen 
can be accumulated after the evaporation of the first two-thirds of the total 
quantity of the liquid. 

The apparatus is constructed so that any particular tray may be connected 
with any particular gas holder by means of the' mere application of simple 
clapper valves, governing the connection between the trays and gas holders, and 
between the different trays themselves. 

We start with the collection of nitrogen almost perfectly pure; then we 
will find in the evaporated gas of each successive tray certain quantities of oxy- 



p^ 



USE. 735 



gen, which will increase continually toward the bottom. Up to the evaporation 
of the first half of the original liquid, the total loss of oxygen will not exceed 
one-fifteenth of its total weight. After the evaporation of the first two-thirds of 
the original liquid, the evaporation of the oxygen will increase constantly, and 
with remarkable rapidity. 

It is easy to increase the quantity of the chemically pure oxygen obtained 
in this apparatus, if desired. For this purpose, it suffices to lead the gases 
evaporated on the trays back to the compressor as soon as they contain over 21 
per cent, oxygen. The ensuing liquid is thus much richer in oxygen, as it again 
enters the separator. To accomplish this, it is only necessary to connect the 
gasometer, containing industrial oxygen, with the suction inlets of the air com- 
pressors. This we call a compound process, which can, of course, be applied for 
the manufacture of chemically pure nitrogen. 

The carbonic acid is collected in duplicate filters, which may be inter- 
changed at intervals during the operation, without interference. Their con- 
struction is quite peculiar, and would require too much time to describe in 
detail. It need only be mentioned that they extract all the carbonic acid out of 
the air. 

If it is desired to increase the quantity of the carbonic acid thus collected, 
this can be accomplished to an extent amounting to i per cent, of all the air 
treated, by pipe connection from the inlet of the compressors to the chimney of 
the power plant, or any other chimney under which coal is burned. The 
ascending gases in chimneys are very rich in carbonic acid, and mix freely with 
the outer atmospheric air, and the percentage can, in this manner, be materially 
increased. This fact is of great importance, as carbonic acid is a product of 
enormous commercial value. 

It is possible to connect any number of trays with one single gasometer 
during the operation, and control, in this manner, the quality of the collected 
gases. An arrangement of electric lamps and windows in each tray will permit 
of regulation by observation. This apparatus for the separation of the gas mix- 
tures can be made of any material, and in different forms, particularly in con- 
nection with a system designed to effectually exclude the radiation of heat from 
the surrounding atmosphere. 

COST OF MANUFACTURE OF THE GASES. 

The many experiments which have been made up to the present time per- 
mit us to state that air can easily be liquefied in all quantities in an apparatus 
built according to the foregoing principle, under a pressure of fifteen pounds per 
square inch. If we consider the results of experiments made as a basis, and 
take into consideration the friction, the clearance and all imperfection of valves, 
and all other losses unavoidable in gas compressors, we can accept that we may 
compress our air to twenty-five pounds, instead of fifteen, which, as before men- 
tioned, would suffice. 

Under these conditions, the work necessary for the compression of one 
cubic foot amounts to exactly 2,038 foot-pounds. Although this work is ac- 
.cepted as excessive, we can calculate that the minimum volume of compressed 
and liquefied air in a 500-horse power plant will be 8,000 cubic feet per minute. 



736 USE. 

This will result, in an operation of twenty-four hours, in the liquefaction and dis- 
tillation of air of 11,500,000 cubic feet. The distillation of this quantity of 
atmospheric air will result, according to previous experiments in 5,300,000 cubic 
feet of industrial nitrogen, and 3,550,000 cubic feet of industrial oxygen. The 
quantity of carbonic acid varies, according to the topographical conditions, and 
to the desire of the manager, between 520 and 5,200 pounds in twenty-four hours. 

COST OF POV/ER PRODUCTION. 

Experience in the electric industry indicates that plants of 500 horse power 
are of satisfactory efficiency. The statistics show that the work of steam plants 
in the vicinity of seaports and large industrial centers in general costs one-third 
of a cent per horse power hour. In this cost are included all expenses of the 
power plant, such as depreciation, operation, coal, wages, illumination, oils and 
small details. This cost of one-third of a cent per horse power hour is in many 
cases high, especially if triple expansion engines are applied. We accept this 
cost, however, in order to be conservative. The operation of a soo-horse power 

steam plant would, therefore, cost in twenty-four hours, 24 X i X 5^ = $40. 

3 
To this cost of operation we have to add the special expenses caused by the oper- 
ation of the separating apparatus and manufacture of carbonic acid. These are : 

First. — Wages of the necessary attendants. Two men suffice, if con- 
tinually present, for the whole operation. One mechanic, day and night, $6. One 
laborer, $4. 

Second. — Maintenance of coolers, small details, and necessary repairs, $6. 

Third. — Depreciation. The initial cost of construction of the complete 
apparatus for separation of the oxygen and nitrogen will amount to $25,000. 
Depreciation of 10 per cent, per year will amount daily to $8. 

Fourth. — Incidentals, $10; or a total of $74. 

Seventy-four dollars will, therefore, cover the cost of production, opera- 
tion and depreciation of all materials. With this daily expenditure we can pro- 
duce, then, 3^550.000 cubic feet of industrial oxygen, 5,300,000 cubic feet of indus- ' 
trial nitrogen, and 3,000 pounds of carbonic acid. 



ON THE LIQUEFACTION OF AIR BY DYNAMICAL ACTION. 



BY PROF. J. E. DENTON, M. E., 75.* 

It is now known, through the labors of several European physicists, that air 
as it exists in the earth's atmosphere is a superheated vapor of a liquid, whose 
boiling point under atmospheric pressure is 312 degrees below the Fahrenheit 
zero of temperature. 

Thus if ^0 (Fig. 279) represents the cubic feet occupied by a pound of 
liquid air at atmospheric pressure, in order to put the substance in the condition of 
natural air at, say, 60 degrees Fahr., the liquid must be conceived to be evaporated 
as a saturated vapor until it occupies the volume Ag, at the constant temperature 

* Stevens' Indicator. 



'■^''^rTi^<: 



USE. 



of — 312 degrees, and to then be further ex- 
pended to the volume AD by superheating the 
vapor to 60 degrees. To generate the vapor, 
or to produce the increase of volume Og, 
would require heat to be supplied equal to the 
"latent heat" of evaporation, which rough ex- 
periments shows to be about 160 British 
thermal units. To produce the increase of 
volume gD would require an amount of heat 
equal to 0.238 [60 — ( — si2)]=8g British ther- 
mal units, if the mean specific heat of the air 
over a range of temperature so low was the 
same as for its natural conditions. The mean 
specific heat may be greater than 0.238, so that 
89 units may be less than the heat necessary 
to affect the superheating effect. 

If the pound of liquid air is put under a 
pressure of 10 atmospheres, and then heated, it 
will not begin to vaporize until some higher 
temperature than — 312 degrees Is created, as, 
say, — 275 degrees. This may be conceived to 
increase the volume of the liquid, as in the case 
of other substances. Then if the liquid was 
all vaporized its volume would be increased by 
o^g^, and the latent heat to affect this would 
be less than that for atmospheric pressure 
vaporization in the proportion of o^g^ to g. 
As the pressure under which the vaporization 
occurs increases, the liquid volume becomes 
greater, and the vapor volume less, so that 
finally there is no difference between them. 
We do not know the relation of the tempera- 
tures and volumes of the vapor and liquid be- 
low 39 atmospheres, but physical investigation 
has determined that the vapor and liquid vol- 
umes become identical at 39 atmospheres, and 
that the temperature is then — 220 degrees. 



M ^ 



c3 O. 



o o 



O c3 P «' 

! II 

03 ej « r 

►5 !l ^'l '^ 




73'^ 



USE. 



At this temperature air must occupy the volume at e if its pressuee is 39 
atmospheres or greater, and it may then be considered to exist either as a gas or a 
liquid. The slightest addition of heat will make it a super-heated vapor, and the 
slightest abstraction of heat will make it a liquid. This temperature is therefore 
called the "critical temperature" of the substance. 

If, therefore, natural air is compressed from the volume AD to, say, 150 
atmospheres, and then stored in a reservoir at 60 degrees, so that its volume will 
be BC, and if then the pressure is maintained constant, and sufficient heat is 
abstracted to more than cool the air to — 220 degrees, it will pass into the liquid 
condition. 

Experiments by Mr. C. E. Tripler in New York, and Dr. Linde in Munich, 
have shown that the necessary abstraction of heat to cool highly compressed air 




FIG. 280. — DR. LINDE's APPARATUS FOR OBTAINING LIQUID AIR. 



from ordinary temperatures to its critical point or possibly lower, can be ac- 
complished by the dynamical effect resulting from the flow of air through a small 
orifice connecting a reservoir at high pressure with one at a much lower pressure. 
Dr. Linde,* and his collaborator, Prof. Schroeter,t of Munich, have pub- 
lished sufficient details of their work to enable the results to be scientifically 
studied. Linde's apparatus is outlined in Fig. 280. A compressor A delivers air 
from the atmosphere to a reservoir B, where it is cooled to ordinary atmospheric 
temperature The air also fills the inner of the two coils C, and is maintained at a 
constant pressure therein, while flow occurs through a throttling cock D to the 
chamber E, which is maintained at a lower pressure by allowing the expanded 

^London Engineer^ i8<)6. 

\Zeitschrift des Vereines deutscher Ingenieure^ Vol. XXXIX. 



r 



USE. 



739 



air to escape through the outer of the coils C. In an experiment in which the 
higher and lower pressures were 220 atmospheres and i atmosphere, respectively, 
the temperatures were distributed as shown in Fig. 281. Curve No. i shows the 
temperature of the air leaving B. Curves No. 2 and No. 3 show its temperature 
at the high and low sides of the throttle D, respectively, and No. 4 shows the 
temperature of the gas leaving the apparatus at F. Liquefaction commenced at 
about the fifth hour of operation. 

It is evident from the curves of Fig. 281 that the flow of the air through the 
expansion cock causes a permanent cooling of the air greater than the radiation 
and friction losses of the apparatus, and that this cooling effect being applied to 
reduce the temperature of the air flowing to the throttling cock continually 
increases the permanent fall of temperature due to the flow through the cock. 
The second column in Table i shows the cooling effect due to the flow in Linde's 
experiment. 

TABLE 72. 



Temperature approachin^j cock. 
Degrees Fahrenheit. 


Fall of temperature by flow 

through cock. 

Degrees Fahrenheit. 


Experi- 
ment. 


8=0.5 (pi-2)2) 


^30 


33 

65 

80 

96 

112 

135 


97 





110 


— 30 


125 


— 60 


132 


—100 


179 • 


— 1')0 Liquefaction commenced 


240 







The proportions of the coil C show that the air escaped with a velocity of 
about 40 feet per second, which is neglectable in its influence upon the temperature 
of the air after expansion. The permanent cooling effect is, therefore, attributable 
to the imperfectly gaseous nature of air, which causes some of the fall of tem- 
perature due to the adiabatic expansion governing the flow, to be absorbed in 
internal work. This cannot be reconverted into temperature like the external 
work of the expansion, when the velocity of the gas subsides. The possibility of 
permanent cooling due to the imperfect gaseous nature of air, for flow through 
a throttling cock, was shown by Thomson and Joule, in 1854. They gave as its 
measure in degrees Fahrenheit : 

pi and p2 are given in atmospheres. 

'i = absolute temperature of air at high pressure side of the expansion cock. 

This formula is the empirical expression of experiments in which pi — Pt 
did not exceed seven atmospheres, and r^ was not less than the equivalent of 32 
degrees Fahr. The-amount of permanent cooling which it would give for the 
Linde experiment is shown in the third column of Table 72. The formula can 
hardly be expected to hold true quantitatively for such abnormal pressures and 



740 



USE. 



yFiQ10 1ll2lB34^€7^ 


i-30 
-t20 

-tic 



-10 
-20 
-30 
-40 
-SO 
-60 
-70 
-SO 
-90 
-100 
-110 
<^-J20 

%-^^^ 
^-MO 

%~iso 

^-170 

^-210 

-220 

-230 

?/3n 




1.1 




. 


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—-^^^^-^^^re^sun^/aimOS. jbZU ^^'' ■. 




^0. l.I^ressure ^eoo^mos. £7iira7?ce air. 


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-2^0 
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-2S0 
-ZQO 
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7 8 9 10 11 12 12 3 4 5^78 

Time -Hours, 



FIG. 281. — DISTRIBUTION OF TEMPERATURES. 



temperatures as are concerned with the liquefaction of air, but it suffices to ac- 
count for the existence of a tangible amount of permanent cooling effect due to 
the flow of the air through the throttling cock in Linde's apparatus, and for the 



r 



USE. 741 



increase in this cooling effect as the temperature of the air at the high side of the 
throttle was reduced. It appears that the actual cooling effect as the temperature 
approached the critical point was about 55 per cent, of the value of (^ given by 

the original formula. This would make (^ = 0.27 {pi — pa) (^) 

The continuous operation of the apparatus finally results in cooling the air at the 
high side of the cock to some temperature h which is, say, above the critical tem- 
perature /c when liquefaction commences. Then if the substance remain homo- 
geneous the process of liquefaction might be as follows: 

Adiabatic cooling by the flov.^ through the cock reduces the temperature 
to the critical point, without reducing the pressure to the critical point, and all 
the air is liquefied. Then as the pressure continues to fall in the jet the tempera- 
tur of the liquid follows saturated vapor laws, and consequently the release of 
heat from the liquid causes vaporization, and since at the critical temperature the 
heat of the liquid is equal to the total heat of vaporization, and the latter may be 
supposed to increase slightly with pressure — the whole of the liquid will be vapor- 
ized to the saturated condition of the lower pressure, and then superheated to the 
amount of the difference between the total heat of evaporation for the critical 
temperature and the lower pressure, respectively. There will also be some super- 
heating effect due to the actual energy of the initial adiabatic flow before the an 
is reduced to its critical temperature. 

Now if the cooling effect ^ due to the flow, acts, and is more than sufficient 
to annul the superheating effect, some of the superheated vapor will be liquefied 
and the resulting mixture will be at — 312 degrees, the boiling point for atmos- 
pheric pressure. This mixture can now act on the air above the throttling cock 
and cool it to the critical temperature, thus liquefying it before it flows through 
the cock. Then the release of heat from the liquid will vaporize and superheat 
as before, but the ^ cooling effect will possibly condense a greater proportion of 
the air to liquid, as the lower temperature at the high pressure side of the throttle 
may have increased <^. 

By the continued action of these conditions liquid can either be drawn off 
from the chamber E, or made to liquefy other air confined in a separate vessel 
lodged in E, or located in the midst of the coils C so as to share with them the 
effect of the return current from E. The separate liquefying vessel may theoretic- 
ally be at any pressure, and the liquid in it be cooled so nearly to — 312 degrees 
that it can be collected in a receptacle under atmospheric pressure without prac- 
tical loss from vaporization. Theoretically, also, the temperature h at the high 
side of the throttling cock might be reduced so far below the critical temperature 
by the return action of the mixture of vapor and liquid from E, that the evapora- 
tive action from the release of heat from the liquid in flowing through the throt- 
tling cock would be exactly neutralized by the cooling effect (^ All of the air 
would then arrive in E as a liquid, but the portion of this which could be with- 
drawn, or used to liquefy other air, would be due to the cooling effect <^, the re- 
maining portion being re-evaporated in the return action to effect the cooling of 
the liquid above tha. throttle below the critical temperature tc. In the German 
experiments the temperature above the throttling cock appears to have not been 
reduced below /c. 



742 USE. 

The amount of liquid permanently producible being dependent upon the 
cooling effect (5-, the algebraic expression of thermal relations according to above 
hypothesis would be as follows : 

Assuming steady liquefaction to be attained, 

^o ^temperature of air entering apparatus. 

ti =temperature of air on high pressure side of throttle. 

/c =:critical temperature. 

t2 =temperature of air on low pressure side of throttle. 

/)i=high pressure, atmospheres. 

p2=\ow pressure, atmospheres. 

n =latent heat of liquid air at p2. 

B. T. U. per lb. 
Ai =total heat of liquid air at pi. 

B. T. U. per lb. 
?'2=total heat of liquid air at p2. 

B. T. U. per lb. 
a =Superheating due velocity of flow before h becomes reduced to tc. 

B. T. U. per lb. 
R =losses by radiation, friction and escape of air at less than to. B. T. U. 

per hour 
J^^weight of air compressed per hour. 
w =weight of air liquefied per hour. 
Ci=specific heat of air between /o and Z^. 
C2=specific heat of air between ti and fc. 
C3=specific heat of air between h and ti. 
Then the whole cooling effect available is WCz (^ — R, which must cover : 

1. The cooling of all the air from /^ to /^ or PVC^ i^o—^i) B. T. U. 

2. The cooling of the whole air from /j to /c or WC.^ {^x—^c) B. T. U. 

3. The condensation of 2a pounds of vapor superheated, 'A^^ — ^^si^^ thermal 

units above saturated condition at t^,or w [_a-\-{7i^ — a^) ']-\-'wr^ B.^T. U. 
Hence, WCJ—R= WC^ (/^_/^)]+ WC^ (/^_/^)+w {a^Ti^—l^-^-r.,) 
w _^ C^6-C\ (/^-/,)-Q {i,-tc)-R 

Let/i = 22o, /q=i, /'^=32, /i = — 200. 

Then (1=0.27 x 22o( ^^ ^ — | =185'' Fahr. 
\46i— 200/ ^ 

7v _i85 C\ — 232 C1--20 C.,— R 

If Ci=o.33, Co=o.4, C^=o.5, r^ = i6o, and a-\-/.i — ^2 = 10. Then -rj^=^-^— ' 

If 7^ = 3, or about 3 per cent, of the cooling effect WCa<\ then ~r= 

yy 42 

This was the ratio of weight of liquid to weight of air compressed in the experi- 
ment to which Fig. 281 refers. The air to be liquefied was in this case confined in 
a separate vessel in the chamber E at about three atmospheres. The weight of air 
compressed per hour was about 85 pounds. 



r 



USE. 743 



111 another experiment about 65 pounds of air were compressed per hour tG 
190 atmospheres, and one-thirty-fifth of it liquefied and withdrawn directly from 
E. Liquefaction commenced in two hours, the weight of the coils being only about 
one-ninth of those used in the other experiment, so that less time had to be 
devoted to cooling the weight of the apparatus. 

Analysis of the liquid product showed it to contain an excess of oxygen in 
both cases. Therefore the air does not remain a homogeneous substance, and this 
fact, together with the absence of any exact knowledge of the specific heats, and 
of the true value of the peculiar cooling influence <">, makes any attempt to calcu- 
late ---- from thermodynamic laws a very rough approximation. 



LIQUID AIR AS A MEANS FOR THE MANUFACTURE OF OXYGEN.* 



BY HENRY MORTON, PH. D., SC. D., LL. D. 

Readers of the Indicator may remember that in the numbers for April and 
July of 1899, beginning on pages 113 and 239, there were published two articles 
by the present writer in which the extravagant claims which had been brought 
before the public for "Liquid Air" as a source of energy, were discussed and dis- 
posed of. 

Since that time, until recently, those interested in the promotion of com- 
panies which propose to establish a business on the manufacture and use of liquid 
air as a foundation, have not been prominently before the public. 

Quite recently, however, extensive advertisements and circulars have 
brought the subject into notice along new lines. 

Though the language of these is largely indefinite or ambiguous, yet it 
does not seem that the former fallacies have been definitely repeated, though they 
are in a way hinted at, but the merits of the scheme are now proclaimed in rela- 
tion to a possible use of the liquid air process as a means for the production of 
cheap oxygen gas. 

Air, as of course all know, is substantially a mixture of four parts of 
nitrogen with one part of oxygen, and when liquefied in the usual way this pro- 
portion is substantially maintained in the liquid. As the liquid evaporates, how- 
ever, the nitrogen escapes much faster than the oxygen, and thus after a time what 
is left will be mainly oxygen, the nitrogen having escaped or been driven off, or, 
as we might say, distilled. If then we pass a stream of liquid air continuously 
into a vessel in which evaporation is allowed to take place, we will in time find 
said vessel to be filled with substantially pure oxygen. 

If this was all and no effort was made to utilize the cold of the evapora- 
tion of the liquid air such a process would be very costly. Mr. Tripler's figure 
for the cost of liquid air, it will be remembered, was 20 cents a gallon, and five 
gallons of "liquid air" would be needed to produce one gallon of oxygen, or in 
other words, each gallon of liquid oxygen would cost one dollar. 

This gallon of liquid oxygen would on expanding to atmospheric tempera- 



Stevens Institute Indicate)'. 



744 USE. 

ture and pressure, give about 104 cubic feet, or roughly, each cubic foot of Oxygen 
would cost one cent, or, a thousand cubic feet would cost $10. 

It is, of course, obvious that by employing "regenerative processes" by 
means of which the cold from the escaping nitrogen and also that from the vapor- 
izing oxygen was transferred to the air which was being liquefied, the cost of 
manufacture could be greatly reduced. 

What that reduction would be there are, as yet, I believe, no data for com- 
putation, but it would without doubt be considerable, so that it would seem prob- 
able that as compared with the chemical methods heretofore in use for the pro- 
duction of oxygen, this new one would be decidedly cheaper. . 

The question which next presents itself is what shall we do with the cheap 
oxygen when we get it? This question is more difficult to answer. The present 
uses for oxygen are very limited, being chiefly for lime lights used in theatres 
and for stereopticon exhibitions and in some refined processes in metallurg>', such 
as the working of platinum the amounts used for these purposes would obviously 
be quite inadequate to support a large business. 

In view of this the "promoters" have naturally turned to the suggestion 
that oxj^gen might be used as a substitute for air in ordinary processes of com- 
bustion, as under steam boilers, in iron furnaces and the like. In this case the 
quantities required would be amply great, but here another difficulty presents 
itself. The cheap oxygen will here encounter the yet cheaper "free" atmosphere 
as a competitor, and in that connection the cost of storage and transportation 
would be prohibitory. 

For example, it has been suggested that if coal burning under the boiler of 
a steamship was supplied with oxygen in place of air there would be a saving due 
to the fact that the heat carried up the funnel by the nitrogen of the air would be 
retained if oxygen only was fed to the fuel. This saving has been, we think, 
incorrectly estimated at so high a figure as 40 per cent. 

The most conclusive way to test the value of such a suggestion is to reduce 
it to a concrete case with actually calculated proportions of parts, volumes and 
weights, as for example, in one of our Atlantic steamers. 

To begin with, every ton of such coal as is used on our ocean steamers 
would require 2>^ tons of oxygen for its combustion,* and if this was carried 
along like the coal supply, the cargo capacity would be fatally reduced, as regards 
weight, even neglecting the strong steel cylinders in which the gas would need to 
be stored, and which would weigh much more than the gas. 

As regards bulk also, even if the oxygen gas was carried under a pressure 



* 1 lb. of carbon requires 2.66 lbs. oxygen for its combustion, and 1 lb. of 
hydrogen requires 8 lbs. of oxygen. 

English steamer coal contains about 80 per cent, carbon and 5 per cent, hydrogen ; 
American steamer coal, about 75 per cent, carbon and 5 per cent, hydrogen. Average 
for both coals, say, 77 per cent, carbon and 5 per cent, hydrogen. 
Oxygen for pounds of coal — 

For carbon 77 X 2.66 = 2.05 

For hydrogen 05 X 8 = .40 

2.45 
or, say, 2i^ lbs. oxygen for combustion of each pound of coal. 



USE. 745 

of 2,000 pounds to the square inch, each ton of coal would require about 500 
cubic feet of compressed gas, and as 2,000 tons is a fair allowance of coal to carry 
one of our large steamers across the Atlantic,! this would mean that about 
1,000,000 cubic feet of compressed gas in cylinders would need to be loaded into 
such a steamer. This volume of gas alone, not allowing for any lost space 
between the cylinders, would be more than 10 times that of the "bunker" capacity 
for the 2,000 tons of coal.t 

If the gas was not compressed then each ton of coal would require about 
66,000 cubic feet of gas, or for as much coal as would carry a steamer across the 
Atlantic, 132,000,000 cubic feet. Now as the capacity of the huge gas-holder 
which is such a conspicuous object in New York City as seen from the Hudson 
River, is 3,500,000 cubic feet, it follows that no less than 38 such gas holders, 
or, if one prefers, balloons of equal capacity would need to be towed along by a 
steamer to furnish it with a full supply of oxygen. This, it is true, does not allow 
for the assumed 40 per cent, saving of fuel, and with that included only 22 
balloons would be required. 

To meet the above, it might be suggested that the oxygen should be manu 
factured as needed on board of the vessel. This, however, would require 
machinery comparable in bulk and weight with the engines driving the vessel, 
and, therefore, this suggestion also fails to relieve the difficulty. 

Another practical difficulty which at once suggests itself to any one familiar 
with the combustion of fuels of any sort in oxygen, is the enormous intensity of 
the temperature produced. A furnace fed with oxygen in place of air would 
melt down or burn up in short order, not because a pound of coal would yield a 
greater quantity of heat if burned with oxygen, but because it would develop 
this quantity with a more intense combustion and so produce a greater and prac- 
tically destructive intensity of temperature. 

The above simple calculations show how utterjy impracticable, not to say 
absurd, is the suggestion that oxygen might be used with advantage in the fur- 
nace of a steamer. 

We have selected the case of a steamer from those referred to by the "pro- 
moters" of the new oxygen process, as involving data easily secured; but it goes 
without saying that the conditions with a locomotive or any other traveling motor 
would be substantially the same, and that even with stationary engines the bulk 
and mass of the oxygen gas to be handled would render its cost prohibitory by 
reason of the first cost and operating expense of the machines required to pro- 
duce and manipulate it. 



fTons of coal required for steamer across the Atlantic. Table in London 
Engineering, 1893, Vol. I., p. 469, gives for the Umbria 1,900 tons. The estimate 01 
I oal for the Campania from the same table is 2,900 tons. The St. Louis has bunlcer 
; apacity for 2,500 tons, Engineering, 1895. 

JSpace requirefl to store a ton of coal, Kent's Mechanical Engineer's Pocket- 
Book, p. 170. To store ton of coal, 2,240 lbs. Bituminous coal, 41 to 45 cubic feet. 
Anthracite coal, 34 to 41 cubic feet. 



746 



USE. 



LIQUID AIR AND ITS USES. 

Air is the vapor of a liquid and acts in its properties like the vapor of 
other liquids ; for it liquefies at a pressure of 573 pounds per square inch with 
the temperature reduced to — 220° Fah., and upon gradual release of pressure 
commences to boil at 294 lbs. pressure with a falling temperature reaching — 312° 
Fah. when the pressure is entirely released, at which temperature it will main- 
tain its stability exposed to the atmosphere for some little time, according to the 
quantity under trial, and holding its intensely low temperature by its own evapo- 
ration until the whole is evaporated. 

The critical point for air, or the temperature above which it will not 
liquefy by increased pressure, has been stated by Prof. Dewar to be — 220° Fah. 
It has been compressed to over 14,000 lbs. per square inch without signs of 
liquefying at ordinary temperatures, and has been used for blasting rock and 
coal at 9,000 lbs. pressure. 

Its use in physical experiments has been a most important one in develop- 
ing the action of intense cold on the tenacity of metals, in chemical reaction and 
magnetic effect under temperatures approaching that of inter-planetary space. 

The lowest temperatures as yet artificially produced was obtained in the 
experiments of Professors Dewar and Wroblewski by the evaporation of liquid 
air by which a temperature of — 346° Fah. was reached, or within 115° of the 
reputed absolute zero ; beyond which, it is claimed, molecular vibration ceases 
and the chemical action between all substances are in abeyance. 

In physical investigation the convenience for obtaining and maintaining 
intensely low temperatures for a considerable time or sufficient for the manipu- 
lation of experiments in physical phenomena is only of recent date, a4id this has 
opened the way for the most noted expansion in the paths of physical research. 

The action of extreme cold on the tenacity of metals has become a most 
interesting inquiry, with results greatly contrasting with former theories and 
tending to show a critical temperature in the tenacity of metals not uniform, but 
widely varying with their crystalline structure. 

Thus with steel, iron, copper, brass, German silver, gold, silver, tin and 
lead, the tenacity has been found to be largely increased from 60° Fah. to — 295° 
Fah., mostly equal to 50 per cent., and in the case of iron to more than 100 per 
cent. ; while the highly crystalline metals, zinc, bismuth and antimony, lose half 
their strength at the lowest temperature. 

A singular incident is the increase in the tensile strength of the fusible 
alloy of tin, lead and bismuth of 300 per cent, at this low temperature. 

The behavior of a magnet at the temperature of boiling liquid air has been 
found to be somewhat erratic, owing probably to the difficulties attending such 
experiments; but with final results of an increase of from 30 to 50 per cent, of 
its magnetic strength by the extreme cooling process. 

In chemical research the field of operation at extreme low temperatures 
is so new that but few results of a positive character have been reached, owing 
to the chemical inertness of all the active elements, as with acids and alkalies. 

At the lowest temperature yet reached, nitric acid has no action upon 
metals, and acids and alkalies may be mixed without evolution. 



IT 



USE. 747 



A most curious physical phenomenon is shown in the condition of meats at 
the extremely low temperature derived from the evaporation of liquid air; mut- 
ton becomes so exceedingly hard that it rings like porcelain when struck with an 
iron rod, and may be crushed into a fine dry powder with a hammer, in which 
muscle, fat and bone are undistinguishable, but mingled as dry sand. 

Prof. McKendrick, in England, has found that microbic life in flesh is so 
tenacious that it cannot be frozen out, even after exposure to— 133" Fah. for 
four days; that on thawing and raising to normal temperature and moisture, 
activity of life is at once manifested. 

The commercial production of liquid air is a very important discovery, 
and the future question ot economy in motive power may be intimately asso- 
"ciated with this liquid. Compressed air, at pressures ranging from 1,000 lbs. up- 
ward, is conducted from an air receiver through a small pipe, is refrigerated to 
expel its moisture, and is then conducted into the apparatus which liquefies it 
completely, without the use of chemicals of any kind, and it flows from this 
apparatus in a stream about the size of a lead pencil (in the apparatus of Linde) 
into a glass insulated receptacle, containing about two gallons. This receptacle 
was filled in a very short time. Of course, being in an open vessel, liquid air has 
no pressure, but its temperature is approximately — 385" Fahr., or 445 degrees 
below the atmosphere at 60° Fahr. Inasmuch as it boils rapidly on the surface, 
owing to its absorption of heat from the atmosphere, it looks like carbonated 
milk -on the surface, but upon dipping some of it out in a glass and observing 
its color through the glass, it has very much the appearance of ordinary water, 
and about the same weight. Its temperature is very deceptive, for as it runs 
from the condenser one may allow it to trickle over the fingers for a short space 
of time, and it appears to have the atmospheric temperature. The truth, however, 
of the matter is that it does not come in contact with the fingers at all ; the 
hand being something like 480 degrees warmer than the liquid, it throws the 
liquid into a spheroidal state and interposes between it and the finger a film of 
atmospheric air. The sensation is very much like pushing one's hand into a 
bag of feathers or into a mercury bath, allowing, of course, for the difference in 
weight between the mercury and the liquid air. If, however, you immerse your 
hand in the liquid a sufficient time to establish a contact, the flesh would be 
burned, the same as if it were exposed to 440 degrees of heat, measured above 
the atmospheric temperature. If a test tube of 1J/2 inches diameter, having a 
couple of pounds of mercury in the bottom, is immersed in liquid air, the mer- 
cury will be frozen solid in a few seconds, and may be hammered out and other- 
wise manipulated the same as lead. An alcohol thermometer of large size will 
be frozen instantly upon being immersed in the liquid. 

An idea of the tremendously low range of temperature may be gathered 
from the fact that it will take several minutes to thaw out the small bulb of this 
thermometer by covering it with the palm of the hand. It is one of the peculiar- 
ities of these substances at these low temperatures, that the surfaces were not 
sufficiently large to absorb heat fast enough to restore their condition, excepting 
after a considerable length of time. 

A tablcspoon|ul of liquid air poured on about a fluid ounce of whiskey 
will freeze it at once into flat scales, giving the whole the appearance and color 



I 



748 USE. 

of cyanide of potassium. This may be emptied out on a table, and will remain 
frozen in that condition for fully five minutes. 

One thing that impresses one is that while all molecular motion is practi- 
cally arrested at this temperature, the odor is perfectly distinct, showing that 
these particles which stimulate the sense of smell are active and independent of 
the temperature. 

A teacupful of liquid air poured on top of a tank of cold water goes into 
its spheroidal state instantly, in globules of about half the size of an ordinary 
marble, which fly around on the surface, leaving a trail of white vapor behind 
them, 

A handkerchief of either silk, linen or cotton, saturated with the liquid, 
will be charred and destroyed just the same as if it were put in an oven and 
browned, though no change of color is apparent. Its evaporation is quite slow 
and it may be carried about for a number of hours in an open vessel without 
entirely disappearing. It probably represents a compression of about seven hun- 
dred atmospheres, and would, therefore, in a confined space, and at 60 degrees 
temperature, represent a pressure of somewhere from ten to twelve thousand 
pounds to the square inch. 

Liquefying air is not a new thing; it has been performed by exerting enor- 
mous pressure or by freezing air to an unusual degree, or by a combination of 
pressure with refrigeration. There are so many uses to which liquefied air can 
be put that scientists hardly know where its usefulness will end if it can be pro- 
duced at a low rate of cost in commercial quantities. 

Among other advantages, air in the portable, cheap form of a liquid, as it 
passes back to its ordinary state, can be used for illuminating purposes by mixing 
its escaping gases with atmospheric air in certain definite proportions. More- 
over, as a driving force in the way of detonators, or explosive material to drive 
engines, liquid air is obviously a power that can be, under given conditions, 
profitably applied. 

Hitherto the classic example of a method to liquefy air and obtain oxygen 
has been that invented by Beatty and Cailletet in 1877. With their machine, one 
began with carbonic acid gas. By means of a pump this gas was condensed in a 
tube, round which lay water at 10 deg. to keep the tube cool. The carbonic acid 
gas, being reduced to a very low temperature, passed from the first tube into 
another chamber with a tube in it, and in so doing fell to a lower temperature. 
Into this second tube was pumped at high pressure ethylene gas, which, in turn, 
fell to a low temperature, owing to the coldness of the carbonic acid gas bathing 
the tube. The ethylene gas was then passed from the second tube into a third 
compartment and fell further in temperature in so doing. The third compart- 
ment had likewise a tube with an air pump attached. Into this third tube was 
pumped oxygen gas and from the ethylene gas bathing it the oxygen gas reached 
a temperature of 192 deg. below zero. Finally, the oxygen was let out into a 
fourth compartment, in which was a fourth tube. The air pump attached to this 
fourth tube having filled it with condensed atmospheric air, the latter was so 
reduced in temperature that when it in turn was released from the tube, its cold 
was 273 deg. below zero, and it appeared in the form of drops like water. 



w 



USE. 



749 



This product, which is called liquid or fluid air, has a milky appearance 
from the presence of some carbonic acid gas, bubbles constantly, and from its. 
enormous cold emits a smoke or cloud like the top of a very high mountain, and 
will only gradually resolve itself again into air when exposed to the ordinary 
atmosphere. 

Fluid air costs about lo marks (say $2.25) for 5 cubic meters reduced. 
The new method is the invention of Professor Linde, of Munich. It produces 
the liquid for 10 pfennigs (say 2^/4 cents) for 5 cubic meters, and it yields the 
product either as a gas or fluid, as one wishes. This is one of the most in- 
genious pieces of mechanism recently known; its chief feature is its economy of 



fi ^. 




FIG. 282. — THE LINDE METHOD OF LIQUEFYING AIR. 



working, for it uses air to refrigerate air. After the pump has worked for a 
certain time, one turns a cock and the liquid air runs out at a temperature of 
273 deg. below zero. 

In Professor Linde's method, an air pump of 5 n. p. condenses air to a 
pressure of 200 atmospheres; this air passes down a spiral tube and is let out in 
a chamber, causing great cold; then it rises and passes on the outside of the 
spiral tube, bathing it and thus cooling the new air that has been pumped into 
the tube to take its place. This cooled air follows on into the chamber, expands 
and again lowers its temperature, then passes on up around the same spiral 
tube; but as its teniperature has become much lower, the new air in the tube is 
still further refrigerated. This circulating process goes on, until the new air 
pumped into the tube reaches the expansion chamber at a temperature of 27.^ 



750 USE. 

deg. below zero, when it drops into the chamber in the form of liquid. Thus 
the air, steadily cooled, is made to refrigerate the newly pumped air more and 
more, until the necessary degree of cold is attained. 

Another idea, which may or may not be an improvement, is to have the 
pump and all parts of the machine kept very low in temperature. 

Air in the cheap, portable form of a liquid rich in oxygen can be used 
for many purposes in manufactures and the trades. The discovery of a cheap 
method may be of importance to American manufacturers. 

We illustrate the ingenious and simple apparatus used by Prof. Linde in 
Germany for liquefying air by a continuous process in which a recompression of 
the cold expanded air is carried in a cycle of continually depressing temperature 
with an inlet of cold fresh air under pressure to compensate for contraction by 
compression and cold, until a temperature and pressure is reached by which a 
portion of the air liquefies and is held in the expansion chamber, from which 
it may be drawn off in a continuous stream, or as wanted. 

In the Linde apparatus, as shown in our illustration, cold compressed air at 
324 lbs. per square inch is furnished to the apparatus at (a), which establishes 
through the suction pipe and outer coil, a back pressure in the liquefying flask 
(G) of about 325 lbs. per square inch. 

The compressor (C) is of the kind used for liquefying carbonic acid gas; 
it raises the pressure from the suction side of 324 lbs. to 955 lbs. on its force 
side, from which the expansion is obtained for producing the low temperature 
required in the flask (G). 

In subsequent experiments a pressure of 3,000 lbs. per square inch has 
been used. 

The high pressure air pipe enters the refrigerator (R) into a coil im- 
mersed in a circulating current of cold brine at about 10° Fah., which reduces 
the temperature of the high pressure air to about 15° Fah. The high pressure 
pipe then enters and is enclosed in the exhaust pipe of the apparatus in a coil 
containing 260 feet of i^-inch pipe, the internal pipe size not stated, but probably 
^:;-inch pipe. The small pipe emerging from the large coil at the bottom, enters 
the liquefying flask with a regulating cock, as shown in the cut. The regenerat- 
ing coil and flask being enclosed in a thoroughly insulated chamber, the operation 
may be as follows : 

Taking the air from the primary compressor at 324 lbs. pressure and at 
normal temperature or less by artificial cooling, say to 30° Fah., the high pres- 
sure compressor carries the pressure with a third of its previous volume to, say 
972 lbs., which will raise the theoretical temperature to, say 520 '^ Fah. 

This temperature should be so much absorbed by the refrigerator (R) as 
to allow at the start of the machine, of a temperature below the normal at the 
expansion nozzle In the flask. The expansion of the air from 972 lbs. to 324 lbs., 
say 3 volumes, or 43 atmospheres, reduces the temperature by expansion, theo- 
retically, to about 400° below zero, Fah.; but in consideration that the material 
of the apparatus is at normal temperature and the specific heat of air being of low 
degree, a large part of this excessive cold must be absorbed in the material of 
the apparatus and its insulation, in order to bring the whole apparatus down to 
a productive temperature. This can only be done by operating the air in a cycle 



USE. 751 

by which the cold produced by expansion in the flask is utilized in the outer 
coil for reducing the temperature of the air in the inner coil. The time required 
for cooling the insulated apparatus to the temperature for producing liquid air 
in the flask was found to be 5 hours; when the machine became a constant pro- 
ducer of liquid air at the rate of six pounds per hour. G. d. hiscox. 



Penn Yan, N. Y., Oct. 6, 1897. 
Editor Compressed Air: 

I have been intensely interested in the paper "Liquid Air and Its Uses," 
and* also in the account recently published in your columns of experiment with 
air at high pressures. 

I have done some experimental work with air at moderate pressures, but 
I am not one of the lucky few who can have the liquid article on tap. 

Mr. Hiscox's admirable article gives us a great amount of valuable informa- 
tion, but still suggests a great many questions to be asked by a worker who 
sought to use liquid air as condensed power. 

First, and probably most important, would be the question, would any 
development so far met with along this line indicate that natural laws make it 
possible or practical for us to realize returns in work for efforts expended in 
producing cold to any such extent as is done with the same amount of effort in 
producing heat? 

Suppose, after having been able to produce or purchase a flask of liquid 
air I wish to realize upon my investment in work? Naturally one might sup- 
pose that if I inject homoeopathic doses of it into a closed receiver it would 
endeavor therein to return to its original volume, and would exert a pressure in 
accordance with the space allowed it. Does it really accomplish this with suf- 
ficient rapidity to generate any considerable pressure? Or will its effort be 
exactly measured by its ability to absorb or extract heat from its surroundings? 
This last would seem to be inevitable, and the question will seem to have been 
unnecessary to those who have the opportunity for investigation. But I believe 
there are many readers who would like to know something about the action of 
liquid air in the process of re-conversion backward under pressure to the point 
where it is air again. Very truly yours, 

frank CAREY. 



LIQUID AIR AND LOW TEMPERATURES.* 

Probably no other discovery of the last quarter of a century has created 
such widespread interest and astonishment as the. simultaneous liquefaction, by 
Messrs. Pictet and Cailletet in 1877, of air hitherto considered as a permanent or 
incondensable gas. This discovery was of little value commercially, however, 
because of the enormous expense of the product, and therefore, outside of its 
value as a scientific achievement it was practically worthless. With the recent 



*Yale Scientific Monthly. 



752 USE. 

announcement, however, by Mr. Tripler, of New York, that he can produce this 
substance in practically unlimited quantities, the value of this product assumes 
more tangible proportions, as the uses to which this inconceivably cold and 
extremely volatile liquid can be put are almost innumerable. 

The evolution of the production of low temperatures has been gradual yet 
wonderful in its development. Two hundred years ago when Fahrenheit was 
striving to produce cold by artificial means for the sake of establishing a zero for 
his new thermometric scale he boasted that no one could obtain a lower tempera- 
ture than that which he had produced by a mixture of snow and ice. Since Fahr- 
enheit's day scientists have been gradually probing the depths of temperature, 
until to-day a point over 400 degrees below the lowest point ever reached by Fahr- 
enheit, has been obtained. 

Three methods for producing low temperatures are known, ist: By the 
rapid solution of a solid. 2d: By the rapid evaporation of a volatile liquid. 3d: 
By the rapid expansion of a cooled and compressed gas. 

Up to 1820 the first method, that is, a freezing mixture, was used entirely, 
and in this manner a temperature of 50 degrees below zero centigrade was 
obtained. 

In 1823, Faraday, by combining pressure with refrigeration, succeeded in 
liquifying all except six of the existing gases, namely, by heating in one limb of 
a sealed siphon a mixture which evolved the desired gas, and immersing the other 
limb in a freezing mixture. The gas was thus liquefied in the cold limb by pres- 
sure proceeding from its own expansion. Faraday reached a limit, however, in 
oxygen, hydrogen, nitrogen, nitric oxide, carbon monoxide, and marsh gas. He 
subjected them to a pressure of 1,000 pounds per square inch, subsequently 
increased by others to 4,000 pounds, without affecting their liquefaction. Hence 
these gases were termed permanent, or incondensable gases, because it was sup- 
posed that they would remain gaseous under any conditions. 

It was not until 1869 when Dr. Andrews, of Belfast, discovered the impor- 
tant fact that unless these gases be cooled to a certain temperature, known as the 
critical temperature, and varying in different gases as the following table will 
show, no amount of pressure will liquefy them. 

CRITICAL CONSTANTS. 

Temperature * Pressure 

in Degrees in At- 

Centigrade. mospheres. 

Hydrogen — ^240 13.3 

Nitrogen — 146 33. 

Carbon monoxide — 140 . 39. 

Oxygen —119 50. 

Methane — 100 50. 

Nitric oxide — 93 71. 

Tthylene +10 51. 

Carbon dioxide.. -J- 32 77. 

Nitrous oxide +53 75- 

Acetylene +57 68. 



* The above equals the amount of pressure required to liquefy a gas when cooled 
to the critical temperature and is known as the critical pressure. 



USE. 753 

This important discovery created quite a sensation in the "scientific world" 
and gave a new impulse to the workers in this field of physical research. Chief 
among these were Pictet, a Swiss chemist, and a French chemist, Cailletet. These 
two men although working and investigating entirely independent and ignorant 
of each other, simultaneously announced to the Academy of Sciences on December 
24th, 1877, their success in liquefying air. The incredulousness of this discovery 
to the public may be compared to that of a skeptical African chief, who, having 
accepted the many reports as related to him by his white visitor, absolutely refused 
to believe him, when he was told that owing to the intense cold in some countries, 
the rivers became so solid that people actually walked over them. 

Pictet cooled carbon dioxide by surrounding it with liquid sulphurous acid 
until a temperature was reached at which it liquefied. (Although at atmospheric 
pressure the boiling point of sulphurous acid is relatively high at reduced pressure 
it is very much lower.) He then obtained a still greater degree of cold, by allow- 
ing the liquid carbon dioxide to evaporate rapidly in an exhausted space. The 
oxygen was generated in the usual way from potassium chlorate, by heating it in 
a strong ir'on retort. In this way a pressure of several hundred atmospheres was 
obtained. The retort was then surrounded by this liquid carbon dioxide, boiling 
in a vacuum, and a temperature finally resulted, which liquefied the oxygen. 

Cailletet's process was practically the same as the one in use at present. His 
method consisted in exposing the oxygen, or whatever gas he wished to liquefy 
to enormous pressure produced by means of a hydraulic press, while at the same 
time the temperature was lowered, by suddenly allowing the gas to expand. In 
this manner a sudden disappearance of heat energy occurred, it being absorbed 
and transformed into mechanical motion. By this method Cailletet succeeded in 
liquefying hydrogen, a gas whose critical temperature is but 33 degrees centigrade 
above the absolute zero of temperature, that is, the point where a gas, if it did not 
liquefy would have zero volume, but as matter is indestructible, it is evident that 
every gas must liquefy before the absolute zero of temperature is reached. He 
was unable to collect any of the liquid hydrogen, however, it merely appearing as 
a mist on the inside of his tube, when the great pressure of 300 atmospheres, to 
which the gas was subjected, was suddenly relieved. The explanation of this 
method is that the gas first of all cooled, on account of its quick expansion, 
because of the transformation of the heat energy into mechanical motion, in tem- 
perature below its critical point and then becomes liquefied under the enormous 
pressure to which it is subjected. 

These results by Cailletet and Pictet, and a few years later Dewar, led to 
the inevitable conclusion that solids, liquids, and gases were but different forms of 
matter through which any substance could be made to pass by the addition or 
withdrawal of heat and pressure. It was held that every known substance, that is 

Iny of the elements, would behave similarly if heated or cooled sufficiently. 
Professor Dewar, of Glasgow, working in the same laboratory in which 
■■araday so successfully experimented, succeeded in 1883 in liquefying all known 
ases except hydrogen and fluorine. Ilis method involved practically the same 
rocess as that employed by Pictet in 1877, except that he cooled and liquefied 
thylene gas, instead of carbon dioxide gas, with sulphur dioxide. Then by means 
of the liquid ethylene, boiling in a vacuum, he cooled air and other gases below 




754 USE. 

their critical temperatures and liquefied them by pressure, due to their own expan- 
sion. To him belongs the credit of first liquefying air in quantity. 

Liquefied air and nitrogen were first collected in any desirable quantity by 
Olzewski, in 1885. Later, by using oxygen as a cooling agent, he cooled a tube 
containing hydrogen under a compression of 150 atmospheres, to 211 degrees 
below zero centigrade, and then by further cooling the hydrogen, by allowing the 
confined gas to suddenly expand to a pressure of only 20 atmospheres, he obtained 
liquid hydrogen. By boiling liquid oxygen in a vacuum he obtained 
a temperature of 225 degrees below zero centigrade. By boiling the liquid 
hydrogen, which he subsequently obtained, in a vacuum, a temperature of — ^264 
degrees C. was obtained, but 9 degrees from that coveted absolute zero of tempera- 
ture, which scientists have sought for as eagerly as have explorers the North 
Pole. Olzewski's process was, however, very complex and expensive. 

The economical liquefaction of air has only very recently been accom- 
plished by Mr. Tripler, of New York, who has for many years been experimenting 
and striving to reach this end. His method is what is known as the "self intensi- 
faction of cold," or the method of the expansion of air under pressure. In short, 
he produces liquid air simply by the expansion of compressed and cooled air, 
without employing any other substance than liquefied air to bring this about. Mr. 
Tripler first produced liquid air in 1890 by the same method used by him to-day, 
only of course with very crude apparatus. His aparatus consisted 
of a compressor connected by a tube to a coil, containing an inner 
tube which has a valve at the top. This coil is in turn surrounded by a 
glass tube 12 in. by i 3-16 in. diameter open at the bottom. Air under a compres- 
sion of 2,000 pounds is forced from the compressor through the coil, up through 
an inner tube, and out a valve at the top. By the expansion of the escaping air, 
the coil and the inner tube were so cooled, that liquid air trickled down the pipes 
and dropped out at the bottom of the tube. The plant as it to-day, after eight 
years of experimenting and testing, consists of a triple air compressor, a cooler 
and a liquefier. The compressor is of the ordinary form having three pumps upon 
one piston shaft, working in a line. The first pump compresses the air to 60 
pounds per square inch ; the second raises this to 750, while the third brings the 
air under a compression of 2,000 pounds per square inch. After each compression 
the air is forced through jacketed pipes, in which it is cooled by city water to 
about 50 degrees Fahrenheit. After the third compression (40 H. P. is used for 
this compression) it flows through a purifier and thence into what is termed a 
liquefier. This apparatus consists of a felt and canvas-covered tube, 15 feet long 
and i^ feet in diameter, placed about 5 feet above the floor. The interior is full 
of pipes and coils. These are in two sets, the first of which contains compressed 
air to be liquefied while the second is filled with compressed air which is to do 
the liquefying. By means of a valve this air is allowed to escape through a small 
hole when it rapidly expands and rushes over the first set of pipes greedily licking 
up all the heat contained in them. Finally after about five minutes, so much heat 
has been extracted from the first set of pipes that the air in them is cooled way 
below the critical temperature, and owing to the intense cold and the enormous 
pressure, this air becomes liquefied. Oftentimes such a cold prevails in the 
apparatus at this stage, that even the air used to do the liquefying is liquefied and 
sometimes even frozen. If now the valve in the first set of pipes be turned, liquid 



USE. 755 

air rushes out in the form of a dense white chilly mist as on exposure to the nor- 
mal air, which is 390 degrees F. hotter than the liquid air, it instantly vaporizes. 

Thus Mr. Tripler makes liquid air at a cost of about 20 cents a gallon. It 
is this fact wherein the value of Mr. Tripler's method lies. The production of 
liquid air by Dewar in 1885 at a cost of $500 a pint, was hailed by scientists as a 
very creditable achievement. From this fact a slight idea of the greatness of Mr. 
Tripler's accomplishment may be seen. 

With some of this liquid air produced by Mr. Tripler, Professor Barker, 
of the University of Pennsylvania, recently performed before the students a very 
interesting series of experiments. By means of this extremely cold liquid, he 
froze mercury and alcohol, the thermometric substances. When iron, tin, steel 
or rubber were dipped in this liquid they became extremely brittle. The tensile 
strength of metals was found to be vastly greater after immersion in this liquefied 
air, and in the case of iron this increase reached 88 per cent. In the same manner 
the electric resistance decreased after immersion, and it is claimed after numerous 
experiments and profuse calculations, that all metals would become perfect con- 
ductors at absolute zero. It is by their practical application of this phenomenon 
that these extremely low temperatures are measured; namely, by measuring the 
resistance of a platinum wire before, and after, immersion in the liquid whose 
temperature is to be measured. Then from these resistances the temperature of 
the liquid can be calculated. 

Perhaps the most startling experiment performed by Professor Barker was 
the placing by Professor Barker was the placing of an ordinary tea kettle contain- 
ing liquid over an intensely hot flame. This caused the liquid to boil terrifically 
and it shot from the spout in straight columns three or four feet into the air. 
The carbon dioxide generated by the flame froze in a solid layer on the bottom 
of the kettle which was but a few inches from the flame. When a glass of water 
was poured into this seething liquid it was frozen solid, although the liquid was 
at a temperature of 191 degrees below' zero centigrade, when the hand was dipped 
into it a sensation indistinguishable from that of a severe scald was experienced. 
If, however, the hand were withdrawn immediately, no injury resulted, because 
the moisture on the hand evaporating, formed a sort of non-conducting cushion. 
When, however, the hand was not immediately withdrawn it was soon robbed of 
its protecting cushion, and severely scarred. When this liquid air was poured 
from the kettle and filtered, to free it from the frozen particles floating in it, the 
liquid was seen to be of a pale blue color. This liquid was almost pure liquid 
oxygen as in the previous boiling most of the nitrogen — the other constituent of 
liquid air — was distilled off, for its boiling point is 13 degrees C. below that of 
oxygen. From the pale blue color of this diluted oxygen, as it still contains liquid 
nitrogen, which is colorless, and from the indigo blue color of ozone, that is, con- 
densed oxygen, a theory has been advanced, attributing the blueness of the sky to 
the oxygen in the air. When phosphorus, for which oxygen at ordinary tempera- 
ture has a great affinity, is brought in contact with liquid oxygen, no combination 
and vigorous combustion results, as takes place at ordinary temperature. Should 
the liquid air be confined in a vessel a terrific explosion would result, as one 
volume of this liquid air will expand to 748 volumes of gaseous air. If placed in 
an ordinary open glass flask, or bulb, the liquid air will rapidly volatilize 
and the moisture in the surrounding air will be condensed and frozen in 



756 USE. 

the form of a shaggy white coating on the outside of the flask. 
A very suitable receptacle for this liquid was devised by Professor Dewar. This 
is merely a double globe with a vacuum between, which being a non-conductor of 
heat prevents the passage of it by convection. Heat is conveyed in another man- 
ner, however, namel}^ by radiation. To prevent this the inside of the outer globe 
was silvered. It was found that liquid air would last lo times as long in a silvered 
Dewar bulb as in an unsilvered one. Another very excellent apparatus for storing 
liquid air consists of four globes, one within the other. In the first or outer space, 
between the first two globes, is inserted a mixture of liquid carbon dioxide and 
ether, which is at a temperature of — no degrees C. In the second space liquid 
ethylene is placed, at — i6o degrees C. In the third space liquid oxygen or air at 
— 190 degrees, and in the fourth space the liquid air to be stored, also at a temper- 
ature of — 190 degrees. With this receptacle, although there is considerable loss 
by evaporation, it is possible to store the liquid air for a reasonable length of time. 
The uses to which this condensed gas can be put are innumerable. Probably its 
greatest future use will be as a source of power. It will be extremely valuable 
for medicinal purposes and surgery. For refrigerating purposes it will be almost 
indispensable. As an explosive it will rival, and even surpass, nitro-glycerine and 
dynamite. w. H. swenarton. 



LIQUID AIR AS A NEW SOURCE OF POWER. ANOTHER ENGI- 

NEERING FALLACY. 



By President Henry Morton, Ph. D., LL. D., So. D.* 

During 1894-5 the present writer prepared two articles under the title of 
"Engineering Fallacies" which were published in this journal, Vol. XL, pp. 273- 
294, and Vol. XII., p. 125. 

Since that time, though several new forms of what might be termed in a 
general way "Perpetual Motion Schemes" have appeared, none of them has 
seemed of sufficient importance to warrant any special notice, but in the March 
number of McC lure's Magazine there is published an article entitled "Liquid Air 
— a new substance that promises to do the work of coal and ice and gunpowder, 
at next to no cost," which is so eminently calculated to mislead the general 
reader, and even to become the basis of financial frauds, like that of the Keely 
motor, that it would seem a duty to draw attention to the fundamental errors in 
scientific principles and in statement of facts which this article contains. 

This McClure article may be fairly considered as made up of two promi- 
nent elements or parts, one of which is the statement of certain things as facts 
which, as I shall presently show, connot possibly exist and are inconsistent with 
other facts stated in the same article and known from other sources to exist as 
so stated ; while the other main element consists of rather vague statements con- 
cerning general principles which, though in a general sense true, yet as here 
used are calculated to cover up or befog the too obvious inconsistencies of the 
statements of facts, with the established principles of science. 



Stevens^ Indicator. 



USE. 757 

As an example of the first element, we find on p. 400 as follows : *'I have 
actually made about ten gallons of liquid air in my liquifier by the use of three 
gallons in my engine." This I shall presently show is simply impossible and 
inconsistent with data given elsewhere in this article and known tfi be sub- 
stantially correct. 

A sample of the other element is found in the following: "That is 
perpetual motion you object. 'No,' says Mr. Tripler, sharply; *no perpetual 
motion about it. The heat of the atmosphere is boiling the liquid air in my 
engine and producing power exactly as the heat of coal boils water and drives off 
steam. I simply use another form of heat. I get my power from the heat of the 
sun ; so does every other producer of power.' " 

This, while true as a general statement of what might be done on an im- 
practical scale, is not correct as here used to imply that in his experiments Mr. 
Tripler actually derives or can derive any adequate amount of energy from the 
heat of the atmosphere or in that sense directly from the sun. This I shall show 
later, but will first take up the statement that three gallons of liquid air have 
supplied or can supply the power to liquify ten gallons. 

On pp. 402 and 403 of the McClure article we are told that Mr. Tripler uses 
to make his liquid air a steam engine of 50 horse-power and that with this he 
can make liquid air at the rate of 50 gallons a day. This 1 know from other 
sources is substantially correct, and means that each horse-power in a day ( say 10 
hours) makes one gallon of liquid air. In other words, one gallon for 10 horse- 
power hours. 

It is again stated in this article on p. 405 that a cubic foot of liquid air 
contains 800 cubic feet of air at ordinary atmospheric temperature and pressure, 
or in other words, any volume of liquid air if adequately heated, will expand 
800 times in reaching atmospheric temperature and pressure. This also is sub- 
stantially correct. We may remark in passing that this is nothing wonderful for 
water when expanded into steam at atmospheric pressure increases about 1,700 
times in volume, or more than twice as much as liquid air. If we apply to the 
above data the well-known and universally accepted formula for the maximum 
work done by air when expanded at constant temperature, 

We find that a pound of liquid air in expanding 800 times would develop about 
190,000 foot-pounds of work. As a gallon of liquid air weighs about 8 pounds 
this would give eight times as many foot-pounds, or 1,520,000. If this work 
were accomplished in an hour it would represent almost exactly ^ of a horse- 
power, because one horse-power means 1,980,000 foot-pounds of work per hour, 
and 1,520,000 is only a trifle over ^ of this. From the above, it follows as a 
matter of absolute certainty that the maximum power which liquid air could 
develop in an ideally perfect engine without any loss from friction or other 
cause would be ^ 0/ o horse-power for an hour for each gallon of liquid air ex- 
pended. 

We have seen, however, that with his 50 horse-power plant, which on ac- 
count of its size, should operate with considerable efficiency, Mr. Tripler makes 
only one gallon of liquid air with 10 horse-pozver-hours. In other words, he re- 



758 USE. 

quires to make a gallon of liquid air 12 times as much power as a gallon of liquid 
air could possibly develop in an ideally perfect engine. 

In face of this, how supremely absurd is the statement that with a little 
engine such as the pictures and descriptions in the McClure article show, lacking 
all conditions for efficient working, Mr. Tripler can make 10 gallons of liquid air 
by the use of three. 

Turning next to the statement about using the heat of the atmosphere to 
develop mechanical energy or work, let us put this to the test of a quantitative 
example. 

Assume the temperature of Mr. Tripler's laboratory to be 70° F. and that 
he has an abundant supply of water at 50° F. These will be of necessity the 
limits of work he can get out of the atmosphere, because any lower temperature 
is only secured by doing work and so expending energy which will be at least 
equal to the power obtainable from the use of such lower temperature. All the 
work that can be obtained for nothing is that which nature will freely give in the 
warm air and cool water, supposing both to be supplied freely without charge. 

The 20° F. which we may assume as being possibly taken out of the air 
by the cool water will represent the maximum gift of nature in this shape of 
"power costing nothing." Now 42 British thermal units, or pounds of water 
changed 1° F. per minute, will represent one horse-power, and as the specific heat 
of air is about % that of water, we would need four times as many pounds of air 
to produce the same effect. This would call for 168 pounds of air changed i** 
F. If, however, the air is changed 10° F. in place of 1° F., we need but ^ 
or 8.4 pounds of air parting with 20° F. each minute, to give us one horse-power 
at 70° F. For "round numbers" let us say 8 pounds. Now a pound of air has a 
volume of about 13.3 cubic feet. Call this also "for round numbers" 13 cubic feet, 
then 8 pounds of air would be about 104 cubic feet, and this volume of air would 
have to part with its 20° F. heat each minute to the apparatus, in order to develop 
one horse-power. For a 50 horse-power engine 50 times as much air would be 
required, or 5,200 cubic feet each minute; this would be the contents of a room 
26 X 20 feet on the floor and 10 feet high, which would have to be drawn through 
the apparatus each minute in such a way as to completely yield its 20° F. between 
70° F. and 50** F. What sort of a boiler or heat-absorbing apparatus can we 
imagine which would absorb from air, at 70" F. 20° F. of its temperature while 
the said air was passing through it at the rate of 5,200 cubic feet a minute ? It 
would surely need to be "as big as a house," to use a familiar phrase. 

This also, be it remembered, makes no allowance for loss by friction, eddy 
currents, and the like which would be enormous, nor for the power to put this air 
in motion. 

Obviously such a machine would be simply huge in size, and indeed the 
friction involved in it would probably use up a large part of the power it could 
develop. 

Suppose, however, that it could be built and operated in place of Mr. 
Tripler's 50 horse-power steam plant. Its entire output would be 50 gallons of 
liquid air a day, and this as we have seen, could only develop in an ideally perfect 
engine |4 horse-power for an hour for each gallon or 3^ horse-power for a day 
of ten hours. This does not look as if heat obtained from the atmosphere and 



r 



USE. 759 



operating an engine by aid of liquid air, was likely to become a dangerous rival to 
the coal mine. 

On p. 402 of. the McClure article it is stated that Mr. Tripler makes his 
liquid air at a cost of 20 cents a gallon. 

We have shown above that the maximum power obtainable from this liquid 
air, by heating it to ordinary atmospheric temperature, is ^ of a horse-power- 
hour. This at 20 cents would be vastly more expensive than power derived from 
an ordinary steam engine, whose cost ranges from less than i cent per horse- 
power-hour under the best conditions to 3 or 4 cents, where a profit is included, or 
the conditions are less favorable. 

The really difficult thing to explain in connection with this McClure article 
on Mr. Tripler and his liquid air, is how those concerned in its publication (being 
as I do not doubt honest men) can be deceived or have so deceived themselves as 
to make and repeat such obviously impossible statements. In this connection, 
however, I will make a suggestion founded on experience. 

Some years ago I was called upon to examine an engine operated with 
liquid carbonic acid, which was said to have ten times the efficiency of an ordinary 
steam engine. 

I, of course, told the applicant that such a thing was physically impossible 
and did not deserve investigation, but finding that a number of substantial people 
had been so impressed by what had been shown them that they would not be satis- 
fied without an investigation, I consented to make one. This proved an easy piece 
of work. I found that the promoters and others were under the impression that a 
horse-power was measured by the raising of 33,000 pounds one foot high irre- 
spective of time, and in their demonstrations were contented with showing that 
their engine did this amount of work in ten minutes. As, however, a horse-power 
involves the raising 33,000 pounds one foot high in one minute, it was obvious 
that the power shown by the carbonic acid engine, was i-io of a horse-power and 
not one horse-power, as those exhibiting the engine claimed. This, of course, 
explained the situation. An engine developing i-io of a horse-power might easily 
require only i-io as much fuel as an ordinary steam engine developing i horse- 
power, without violating any of the established laws bearing on this subject. The 
curious thing was that such people as were concerned in this matter, should have 
been misled on such a simple and elementary subject; but if they were, as I 
personally know, so misled, why may not Mr. Tripler and his friends be in a 
similar case? 

I could give from my own personal experience many like examples, but 
have said enough for the present, to make it evident that what is claimed in this 
McClure article for liquid air as a new source of "power which costs nothing," is 
not founded on fact, but is probably the result of some oversight in observation or 
calculation not inconsistent with honesty of intention. 



THE POSSIBILITIES OF LIQUID AIR.* 

At the outset it must be understood that in dealing with the present subject 
the writer does not wish it to be inferred that what he calls possibilities are in his 

* Engineering Magazine. 



76o USE. 

judgment probabilities of the near future, or, that we are upon the eve of any 
great revolution in engineering methods as the outcome of the recent laboratory 
'studies of liquid air. Much further study and much additional data are required 
before anything more than mere suggestion can be made in this fascinating field; 
for, say what we may, the subject possesses an attraction for those who are 
accustomed to look ahead, remembering that the laboratory experiments of one 
day and generation have often in the past become the foundations of great indus- 
tries. It took three-quarters of a century for Davy's electric arc to develop into 
the beginnings of commercial arc lighting and nearly fifty years elapsed after 
Faraday's brilliant researches in magneto-electricity before dynamos became a part 
of engineering. Yet Faraday had built a primitive dynamo and its reversed form 
was known in primitive types of electric motor. 

Who would have supposed, when ammonia gas was first liquefied by pres- 
sure, that before the close of the century companies would be doing business by 
sending it about in pipes for refrigeration ? Yet such is the fact. 

The splendid studies in liquid air and other gases carried on by Professors 
Dewar and Fleming, on the very spot where Faraday had made his memorable re- 
searches in the liquefaction of gases, form a fitting sequel to the work of that 
great pioneer. 

The object of the present article will be to suggest rather than predict di- 
rections in which, under certain conditions, liquid air may possibly become a 
factor in engineering. And in the absence of favorable conditions need it be said 
that such possibilities will not be capable of realization? 

Let us assume the availibility' of some innocuous gas liquefiable at about 
one hundred atmospheres pressure, at temperatures easily and cheaply attained, 
and at no cost for the gas itself. In such a case there can be no doubt of its soon 
finding enormous application in the storage and recovery of energy. Cheap power 
would be used to compress and liquefy it, after which it would be stored in quan- 
tity, either at atmospheric pressure or at some selected higher pressure. Such a 
liquefied gas would be stable, or remain in the liquid state, if heat were prevented 
from reaching it. This could be done, not perfectly of course, by surrounding 
the containing vessel with a liberal thickness of some good non-conductor of 
heat. That part of the gas which would inevitably escape on account of the lack of 
perfect heat-insulation would be cold and would be made to traverse the non- 
conducting covering in successive layers from within outward, and thus assist in 
cooling the covering and in preventing access of heat to the liquid ; or, the escap- 
ing gas might even be made available for power in an engine, if the liquid were 
kept under a proper working pressure. In this case further heating of the gas, 
analogous to superheating of steam, could be employed before sending it to the 
engine. But little of the energy of the heat so added would be lost, and a consid- 
erable part of it could be supplied by the surrounding air or by water. 

With such a liquefied gas produced at one place by cheap power and carried 
to another for evaporation and recovery of power, ice could be made as a by- 
product. 

In many plants used for the development of power on a large scale, a 
twenty-four hours' output is not called for, but could be attained at but 
slight additional expense. The excess power from such a plant needs some 
means of ultilization. This excess power, as during periods of otherwise 



r^ 



USE. 761 



light load, could be employed to liquify the assumed gas. On a 
large scale this procedure would not be costly, supposing the use of highly 
developed machinery. The liquid product could then be transported in tanks pro- 
vided with heavy lagging and special arrangements to prevent access of heat from 
the outside. Perhaps it could be distributed by a well-covered pipe-line. The 
unavoidable evaporation which would be involved in the pipe-line transportation 
might not be altogether a loss, for if the line be under a pressure suitable for 
engines the escaping gas might possibly be tapped out at intervals, heated, and 
used for power along the line of way. 

But the foregoing considerations are based upon the existence of a gas at 
no cost, with desirable properties rendering its liquefaction easy. Such a gas does 
not in fact exist. There then arises the question whether we can render available 
any of the gases known to us. Carbonic-acid gas is cheap, but still far too costly 
for use in the way proposed. It would not pay to send it back long distances for 
recompression and reliquefaction. It costs too much to be thrown away after 
it has been once used. 

The air itself meets the condition of no cost for material in the case. We 
owe much the larger part of our present knowledge of the properties of liquid 
air to a brilliant series of investigations undertaken some years ago by Professor 
Dewar at the Royal Institution in London, and continued later by Professors 
Dewar and Fleming conjointly. The effects of the exceedingly low temperature 
attained by the evaporation of liquid air, upon electric conductors, dielectrics, elec- 
trolytes, etc., have been carefully studied by them. Few are able to appreciate 
the labor and painstaking effort that must have been expended in these researches. 

In culmination, Professor Dewar has indeed lately succeeded in reducing 
even hydrogen to a liquid and in collecting quantities of it. Temperatures not 
far removed from absolute zero ( — 273 degrees C.) are obtained by the evapora- 
tion of liquid hydrogen. But the absolute zero, like the dynamo of 100 per cent, 
efficiency, may by each advance be more and more closely approximated but never 
reached. This low-temperature research has shown that at temperatures as low 
as — 200 degrees C, attainable by evaporation of liquid air, conducting metals, as 
copper, platinum, silver, etc., when in a very pure state, have their conductivities 
so much enhanced that electric currents flow with but a fraction of the resistance 
experienced at ordinary temperatures. Research has shown that at absolute zero 
they would become perfect conductors. Professors Dewar and Fleming also 
found that liquid air is a very perfect insulator, and that ice and many frozen 
electrolytes even become excellent insulators at the temperatures of liquid air; 
and in general that intense cold in insulators improves the insulation, just as it im- 
proves the conductivity of conducting-metals when they are pure. 

Unfortunately, however, the liquefaction of air requires rather extreme 
conditions, and in the early work of Dewar was an exceedingly costly process. 

The discovery of the fact that air compressed, cooled and collected in a 
reservoir at from 100 to 150 atmospheres might be made to liquefy a portion of its 
own volume, rendered possible the procuring of liquid air by a more direct and 
simple means. This discovery is claimed by several persons, the merits of whose 
claims will not be here discussed. When highly compressed air escapes from a 
suitable orifice it is cooled by its own expansion. If the cooled air be now caused 
to circulate around a long coiled pipe, which brings the compressed air to the jet 



762 USE. 

in such a way that the portion of pipe nearest the jet is the first to be met by the 
cooled air, and so back progressively from the jet; further, if the whole be thor- 
oughly jacketed by a non-conducting covering, the temperature at the jet soon 
falls sufficiently low to cause liquefaction of a portion of the air even at ordinary 
atmospheric pressure. The operation itself is cumulative or self-intensifying, 
since the cooling due to expansion is employed, on the regenerator principle, to 
cool most effectively the compressed gas on its way to the jet and ready to expand. 

If air be compressed to about 800 atmospheres it may be made to occupy 
the same space as it does when liquefied, but even at higher pressures it would 
remain gaseous. Ordinary temperatures of the surrounding air are far above 
the critical temperatures of the gases composing it. In order that it may liquefy, 
it must lose kinetic energy or be cooled; the velocity of the moving molecules 
must be brought down. The removal of heat is essential, and the process of lique- 
faction can only be carried on by cooling the gas during or after compression. 
Conversely, liquid air confined in a closed and filled receptacle, when allowed to 
regain the heat lost in being liquefied, would become gaseous and exert a pressure 
of about six tons per square inch. 

That the processes for producing liquid air will be developed so as to reduce 
the cost to an extent such as to render it available in place of a more ideal gas 
would be a vain prediction to make at present. 

Liquid air consists chiefly of a mixture of four parts of nitrogen to one of 
oxygen. The presence of the oxygen is a disadvantage, inasmuch as fierce com- 
bustion, if not explosion, may be occasioned by bringing liquid air into contact 
with combustibles in presence of a spark or fire. Fine cotton fibre and such like 
substances soaked in liquid oxygen are highly explosive. It is easy, however, to 
separate the oxygen from the nitrogen by fractional distillation at low tempera- 
tures, or methods may be employed to condense the oxygen separately from the 
nitrogen. Doubtless, oxygen gas so separated from its companion would have a 
value in chemical and metallurgical processes. The remaining nitrogen liquefied 
would be perfectly safe. Can it be transported? 

The fact that a three-gallon milk-can of liquid air was brought by Mr. 
Tripler, of New York, from that city to Lynn, Mass., a journey occupying nine 
hours, and that not more than one-third of the liquefied gas was lost, although the 
only covering for heat-insulation was about 2.y2 inches of ordinary steam-pipe 
felting, goes far toward indicating the possibility of transportation. With a tank 
of 20 times the linear dimensions of the milk-can referred to, the surface for loss 
of heat would rise to 400 times while the capacity would have increased to 8,000 
times, and with no better lagging it is easily seen that the daily loss would then 
be not over 5 per cent. Doubtless, however, improved means for heat-insulation 
would make the loss but a fraction of this amount. If the tank were kept under 
a pressure of, say, 200 pounds to the square inch, a suitable safety-valve being pro- 
vided to prevent excess of pressure, the evaporated gas or air could be made to 
do work, especially if superheated. If the tank were in a train the motive power 
might, at least in part, be derived from the normal evaporation from the tanks. 
Further, let us imagine a pipe-line well insulated for heat, and it is easy to see 
that if the velocity of flow equalled the train-speed in the journey of the milk-can 
from New York to Lynn, the percentage loss in a pipe of the diameter of the milk- 
can with no better lagging than is possessed would be the same or even less. 



USE. 763 

Here again perfection of heat-insulation might make quite a saving, and the evap- 
orated gas might, if the line were under pressure, be made available for power 
along the line of way. 

Whether the liquefied gases of the air can be employed in this way, will, 
however, depend upon the development of efficient methods of extracting the heat 
and effecting condensation of the air. That liquid air possesses no advantage for 
refrigeration is without doubt true, unless the refrigerating effect be obtainable 
as a by-product, so to speak, of energy convej^ance. 

Liquid air represents air compressed to about 800 atmospheres, but exist- 
ing without pressure. No heavy and excessively strong tanks are needed for stor- 
ing it. If it be pumped into a closed receptacle, under regulated pressure it may 
be evaporated by the heat of the air, or that of surrounding objects, or it may 
receive heat from bodies imdergoing refrigeration, as water being converted into 
ice; after which heating operation it may be further heated to the melting-point 
of lead by heat of combustion, and be finally used in a suitable engine where its 
expansion may develop power. During its expansion and delivery of power to 
the pistons of the engine it may become so cooled as to be discharged from the 
exhaust at nearly normal atmospheric temperature and pressure. 

The power expended in compressing and liquefying air is, of course, con- 
verted into heat and thrown away. The product, liquid air, has no inherent power 
of energy in itself. It represents negativity, bearing somewhat the same relation 
that an exhausted globe does to the surrounding air. It may become the means 
for rendering the normal energy in the surrounding air available. Liquid air has 
capacity for taking up the ordinary heat pressure of surrounding objects 
and thus acquiring pressure. It can be superheated very efficiently, and 
so used in the form of compressed air in an engine. The superheating 
will, of course, tend to raise greatly the total efficiency. The inevitable 
losses in the compressing and liquefying processes would in part be made up in 
the added heat, the amount of which is small and efficiently employed. We have 
no reliable data of large-scale operations, and can as yet reach no certainty as to 
the efficiency attainable in compression and liquefaction or in recovery of power. 
It is possible that the separation of oxygen which would probably possess a value 
in metallurgy, might tend to diminish the cost of condensation. So also the 
refrigeration which is obtained during evaporation might help the recovery end. 
Where so much is "in the air" we must be content with suggestions only, and they 
may never be realized in practice. The power required to be expended in liquefy- 
ing a given amount of air can be approximately estimated, and an assumed effi- 
ciency of plant may be made to do duty in place of exact figures where none are to 
be had, and if the conclusions based thereon are understood as tentative and sub- 
ject to extensive modification in view of further advances in our knowledge, no 
harm is done. 

In making an estimate of the cost of liquid air as produced on the large 
scale, the factors of plant-efficiency, maintenance, etc., come in to a greater or less 
extent. Assuming that air be compressed as nearly isothermally as possible, and 
^^at in a large plant a possible total efficiency of seventy per cent, might probably 
Hk realized, each horse-power hour might thus be expected to compress nearly 
^^o pounds of air to a pressure of 2,000 pounds to the square inch. If such com- 
pressed air, on being expanded in a very carefully arranged self-intensifying 



764 USE. 

apparatus should condense 25 per cent, of the air admitted we would have about 
254 pounds of liquid air per horse-power hour. The assumed proportion, 25 per 
cent., seems not improbable in view of all the data — meagre enough, it is true — 
which have come to the writer's knowledge. 

If the power cost be taken at $20 per year in large units and an additional 
charge of $10 be allowed for each horse-power of the compressing and condensing 
plant, its interest, maintenance, and operating expenses, the cost per pound of 
liquid air would be about one-sixth of a cent, assuming the plant to run 7,200 
hours per year. This estimate, subject to modification from the very nature of the 
problem, would make the liquid air cost for production about 8 cents per cubic 
foot. If oxygen, separated by fractional distillation, possessed a value for equal 
amounts in excess of the cost of the air the remaining nitrogen would, of course, 
be producible at a lower figure. 

It is probably within the possibilities that a cubic foot of liquid air or 
nitrogen, if allowed to heat from its surroundings and then be further heated to 
200 degrees C, could, in a high-pressure engine, yield about five horse-power 
hours. If at the same time the vaporization of the air were attended by useful 
refrigeration, as in making ice, the cost of recovery would diminish. Need it be 
said here, however, that even if the cost of horse-power of recovered energy much 
exceeded that which is indicated in the foregoing estimates or assumptions, a 
demand may still exist for a source of power having great compactness, freedom 
from nuisance, no heated nor noxious exhaust, and of unequaled controllability? 
The horseless vehicle problem certainly presents us with an instance in point. 

It would seem, however, that certain uses may be found for liquid air in 
which considerations of cost are not so important as is the ability to obtain the 
effects in view. In warfare, for example, the possession of highly concentrated 
energy-stores under control is very important. Liquid air can be rapidly con- 
verted into compressed air at six tons per square inch. This would probably be 
useful in the projection of high explosives. Compressed air is now used for 
propelling mobile torpedoes, or fish-torpedoes as they are called. Dirigible tor- 
pedoes either depend for power upon compressed air or the electric energy of a 
storage battery. Compressed air requires high pressures and very strong and 
heavy containing-vessels. Liquid air can be stored without pressure or at low 
pressures, and can be evaporated at any desired pressure, while its bulk repre- 
sents that of air under 800 atmospheres. A storage battery would probably be 
from five to ten times as heavy as liquid air in a receptacle, for equal available 
energy. But no storage-battery could be discharged at an equivalent rate. 

Submarine boats and flying machines may yet find use for liquid air. In the 
submarine boat it could be evaporated by the heat of the surrounding water, and 
after furnishing power it would ventilate the boat. Before its final discharge 
it could be burnt with oil in a fuel-engine for further power. We may find use 
for it in the flying machine. For emergency work it could in evaporating cool the 
cylinders of a fuel-engine and yield power as a result. Moreover, control of the 
submergence of a boat could be effected by the use of liquid air, so easily gasified, 
to add to the displacement. 

The great feature of the application of such a power as liquid air would be 
its emergency value. By this is meant the ability to obtain at will a sudden output 
far beyond the normal. Animal power notably possesses this emergency value, 



wr 



USE. 765 



and the success of electric trolley systems largely depends upon the fact that, when 
needed, the station can be called upon for a temporary delivery to any single car 
or train, of a power greatly in excess of the rated output of the motors. 

Suggestions have already been made of the use of liquid air or oxygen, 
mixed with combustibles as a high explosive. Such an explosive can be made at 
the time of use, and if left unexploded, either by accident or design, soon loses its 
dangerous character by evaporation of the liquid gas. 

Liquid air may also be used in the rapid production of high vacua. Let 
the bulb to be exhausted be filled with a gas such as carbonic acid, more con- 
densible than air, and be provided with an extension that can at any time be sealed 
off. If now the extension-piece be immersed in liquid air the condensible gas will 
be taken from the bulb and deposited in the solid state in the extension-piece. 
This is now sealed off, leaving a high vacuum in the bulb, particularly if the same 
be heated during the process. 

A fascinating speculation for the electrical engineer is the possibility of so 
cooling the conductors of electric lines or apparatus as to improve the con- 
ductivity many times, and so diminish the losses in any given length of conductor, 
and at the same time greatly improve the insulation. Professors Dewar and 
Fleming have shown, however, that it is a condition of this enormous improve- 
ment in conductivity that the metals be very pure, a very small percentage of im- 
purity greatly lessening the result. As regards the insulation, they have shown 
that dielectrics and even electrolytes become insulators of excellent character 
when cooled to the temperature of liquid air. What effect such a lowering of tem^ 
perature would have upon the dielectric strength or striking distance between con- 
ductors at great differences of potential is not as yet determined, so far as the 
writer is aware. The result to be expected from a consideration of the effect of 
heating upon dielectric strength or striking distance is that very low temperature 
will make it far more difficult to break down insulation by sparking through it. 

That the electrical engineer covets just such agencies as will thus extend 
the range of possibilities in his art needs no proof. He would be apt to choose 
a pipe-line conveying liquid air as the very best location for his conductors, 
assumed to be made of as pure metal as possible, the high insulation probably 
attainable being the chief object. Whether his conductors were placed outside 
such a pipe or within the same, he could no doubt adapt himself to the conditions, 
provided he could get the benefit of the low temperature insulation, and possibly, 
to a certain extent, a gain in conduction. 

It is indeed very questionable whether a pipe-line will ever be laid and 
kept filled with liquid air solely for its electrical benefits, but if such a line were 
also used to supply liquid air to a distant point and the normal evaporation 
utilized, the case would be somewhat modified, though the improbability of such 
a combination being put into service, at least within any reasonable period, still 
remains. 

It will be the proper attitude for the conservative and at the same time 
progressive engineer to await the possession of full and accurate data before 
draw any conclusions as to future practice. Suggestions of possibilities are, of 
course, useful, even if only a fraction of them prove realizable, and no attempt is 
here made to do otherwise than call attention to matters which must from their 
nature possess more or less of interest. elihu Thomson. 



766 USE. 

LIQUID AIR FOR AUTOMOBILES. 

We none of ns know now as much as we will know a little later about 
the best methods of using liquid air, whether for power, for refrigeration or for 
other service, or of the practical value of the effects realized in proportion to the 
cost. As it has been suggested that liquid air may be made serviceable for the self- 
propulsion of road vehicles, it seems to be in order to offer some suggestions 
or to indulge in a little speculation, as to the way to do it and as to what would 
come out of it. 

Liquid air represents, among other things, stored energy, and energy which 
may, partially at least, be reconverted and employed for our service. Liquid air 
is compressed air in an easily portable form. The advantage which it has over 
high-pressure, non-liquefied, compressed air is that it is not dangerous to convey 
or to hold, and that it does not require many and costly bottles to contain it. 
The liquid may be carried in a milk can, or in anything that will hold water, and 
which is merely strong enough for the weight of the water without any added 
pressure, although it is quite imperative to surround the vessel with large quan- 
tities of heat-insulating material. Even with abundant insulation provided, a 
given charge of compressed air in liquid form must weigh much less than the 
same charge under high pressure, and not liquefy but contained in the necessary 
steel bottles. The shape of the vessel in which the liquid may be conveyed may 
be made to conform to the conveniences of the vehicle, while high-pressure air 
insists upon its long cylindrical receivers, which must be disposed of as best they 
may. 

In the previous article I spoke of using liquid air for maintaining supplies 
of compressed air in receivers of considerable capacity, and where the use of the 
air was slow or intermittent, the liquid air being occasionally inserted in charges 
sufficient to restore the fallen pressure in the receiver within certain predeter- 
mined limits. An entirely different system would have to be followed in the 
case of the automobile. All the liquid air for a trip, or for a run between 
charging stations, would be carried in the liquid state, and usually in a single 
receptacle, and there would be practically no compressed air reservoir, or any 
receptacle required for any considerable volume of compressed air after its 
re-evaporation. The liquid air would be pumped into the working compressed- 
air system just as it was wanted for use, and almost precisely as the feed water 
is pumped into a steam boiler. The boiler in this case would necessarily be of 
the tubular type, with the important difference from the steam boiler that the 
requirements for the evaporation of the air would not call for the assembling 
of the tubes in close proximity to each other and around or over the fire, for 
there would be no fire. The heat required would be obtained from the sur- 
rounding atmosphere, and the tubes, or the single continuous tube, would be so 
disposed as to get the best exposure to the air. In the automobile it would be 
most natural and proper to have the air traverse a coil spread out in front of the 
machine, so that the air would strike it with some velocity when the vehicle was 
in motion. After the air had by this means attained the temperature of the 
external atmosphere, its mechanical status and value would be precisely the same 
as that of compressed air which had been produced directly, by compression in 
the usual way, except that the liquefied and re-evaporated air would be abso- 



r 



USE. 767 



lutely dry air, and would be entirely incapable of causing any trouble by freezing 
up in the passages of the motor. The air after attaining normal temperature 
might be passed through a reheater, heated by a little oil lamp or other means, 
and the consequent increase of volume would add considerably to the efficiency 
of the air as in other cases. If the air was used in a compound motor, it should 
certainly be passed through a reheater hrst, and also again before entering the 
low pressure cylinder. If the latter re-heating was not effected there would be 
little or no reason for compounding. 

With this general scheme for using liquid air for an autocar motor, the 
vehicle that I have in mind just at present is a tricycle for a single person, and 
to be used for service similar to that of the present bicycle. Say that we have 
a receptacle that will hold 50 pounds of liquid air, or something over 6 gallons, 
and that 10 pounds of the liquid will be evaporated and lost during our trip 
through the park and up the boulevard, leaving 40 pounds of liquid air available 
for use. Our working pressure will be, say, 100 pounds to the inch. As a cubic 
foot of air at ico pounds weighs, say, 6 pounds (see preceding article) we have 
available 40 -^- 6 = 66 cubic feet of air at 100 pounds. Our motor has a i-inch 
diameter cylinder, 2 inches stroke, normal speed 300 revolutions per minute; 
connected to the driving wheels by differential gearing of wide range. Cutting 
off at quarter stroke, the mean effective pressure will be 44 (see Richards' "Com- 
pressed Air"), and the theoretical power developed will be: i^ X .7854 X 44 
X 100 feet piston speed -^ 33,000 = .1047 horse-power, and the air consumption 
per minute will be i" X .7854 X 4'' x ^ x 300 -^ 1,728 = .1363 cubic feet, to 
which we should add 10 per cent., making the consumption .15 cubic feet per 
minute. As we have 66 cubic feet available, the charge should last 66 -J- .15 = 
440 minutes, or say 7 hours, which, at 8 miles an hour, should be as far as any 
one should want to ride at one time, and it would only be necessary to pour 
in the liquid air again to be all ready for a ride as far again. With liquid air 
in sight as low as 2 cents per pound, this riding is distinctly cheaper than the 
maintenance of a horse. In the few figures here given nothing is said about the 
gain that might be accomplished by reheating. This it would be very proper to 
go into for larger vehicles, and also the compounding of the motor. With air 
at an initial pressure of 200 pounds, and reheated both before entering the first 
cylinder and also intermediately, it should be easily possible to show results 
50 per cent, better than here indicated. Frank Richards. 



I 



LIQUEFYING HYDROGEN. 



London, May 11. — Prof. Dewar has succeeded in liquefying hydrogen, 

which is an unprecedented feat, despite the successes claimed by some theorists. 

Prof. Dewar produced half a wine glass full of the -liquid in five minutes. The 

process is applicable to any quantity. The boiling point of the liquid is 240** 

low zero, Centigrade. Scientific men regard the feat as being of immense im- 

rtance, apart from its enormous scientific interest. By use of liquid hydrogen, 

rof. Dewar has also liquefied helium. — N. Y. Sun. 



768 USE. 

LIQUID AIR AS A CURE. IT WILL STOP SKIN DISEASES, BUT WILL 

NOT KILL BACILLI. 

Dr. A. Campbell White has been experimenting with liquid air in its 
effect on disease and disease germs. Dr. White first experimented with cancer at 
the Vanderbilt Clinic. He found" that liquid air not only had a curative effect on 
cancer, but on erysipelas, abscesses, sciatica, carbuncles, neuralgia and blood 
tumors. Dr. White will not declare the cancer and lumpus patients permanent 
cures, because sufficient time has not elapsed to demonstrate that the poison is out 
of the system. He hopes for the best, however. 

Dr. White operates on his patients in a simple way. His liquid air flask is 
so arranged that the vapor issues from a small aperture. As liqiiid air evaporates 
its volume increases 800 times. Consequently there is plenty of pressure within 
the flask. Dr. White directs the vapor against the sore. As the vapor strikes 
the mark it congeals and coats the sore with frost, which dissipates, however, in 
two or three seconds, as the stream of vapor is turned off. Abscesses, boils and 
carbuncles succumb to one application of liquid air vapor. A quarter of an hour 
is ample time for ordinary cures, though, as the doctor says, whenever pus has 
formed in large quantity it is well to anaesthetize with liquid air, incise and evac- 
uate. In all cases the application of liquid air relieves the pain instantly. Slough- 
ing does not follow except in the case of fairly well advanced carbuncles, and in 
some abscesses when the overlying skin has lost its life by tension and inflamma- 
tion. But in these cases the slough is only superficial, and the ulcer left heals 
rapidly. 

Dr. White praises liquid air as an anaesthetic, and says that it has the ad- 
vantage over every other. Its greatest benefit is that it prevents hemorrhage. 

Dr. White also has been experimenting with liquid air to kill germs, but 
this, he is satisfied, it will not do. It is known that 160 degrees of heat will 
destroy all forms of germ life, but liquid air, 312 degrees below zero, has no effect 
so far as he can find. He has experimented with typhoid, anthrax and diphtheria 
bacilli. The doctor says : 

"These experiments show that liquid air is not an antiseptic, and that germs 
can resist a temperature of 312 degrees below zero, even though exposed to it for 
a long time. I hope to make experiment before long by exposing bacilli to liquid 
hydrogen. I think intense cold may hinder the activity of germs temporarily 
without destro3'-ing their life. 

"By the means of liquid air we may be able before long to distribute cold 
throughout our houses in the summer as we now distribute heat in winter. Cold 
is stimulating and invigorating." — Cold Storage. 



LIQUID AIR AS A BLASTING AGENT. 

Although a reaction has promptly set in against the exaggerated opinions 
on the prospects of liquid air, in which the press indulged, the difficulties which 
the application of condensed gases of so low boiling points involves do not appear 
to be well understood. Some experiments, conducted by the Vienna Crystal Ice 



USE. 769 

Co., in the presence of representatives of the Austrian Technical Military Com- 
mittee may, therefore, be of interest. We do not regard the experiments as by any 
means decisive, since they were certainly not made under favorable circumstances ; 
but they are instructive. The liquid air was obtained from the Linde Company 
in Munich, and was transported in open flasks provided with a Dewar vacuum 
jacket. The flasks were packed with felt and cotton; over the open neck, which 
projected through the lid of the wooden case, a cap of felt was loosely fitted. 
When despatched, the liquid contained a mixture of oxygen and nitrogen in the 
ratio of 75 : 25. During the 72 hours which elapsed before actual use, the greater 
part of this time being spent on transport, half of the liquid had evaporated, and 
the remaining liquid contained 85 per cent, of oxygen', nitrogen is more volatile 
than oxygen. Two kinds of cartridges were made of kieselguhr, mineral oil 
(solar oil) and the liquid. In the first case, the kieselguhr and oil were mixed in 
a wooden basin, the liquid added gradually, and the paste ladled into paper cart- 
ridges clothed with asbestos. In the second case, the earth and oil were charged 
into the cartridge, which rested in a double sheet-metal cylinder with a separating 
layer of felt, and the liquid air gradually poured into the cartridge until the mass 
was thoroughly impregnated. In both cases the formation of mist and of hoar 
frost sufficiently indicated how much of the oxygen escaped during the prepara- 
tion. The cartridges could be handled, but the men did not care to squeeze them 
in firing the primers and detonators ; as a consequence one cartridge missed fire. 
Holes, 30 inches deep, were bored in rock. It resulted that these so-called 
oxylignit cartridges were hardly strong enough, as too much oxygen had evapo- 
rated. The cartridges of the second type did not prove so powerful as the others, 
probably because the lead cases furthered evaporation, especially from the bottom 
of the cartridge. On the results, Artillery-General-Engineer Hess has commented 
to the following effect : The preparation of the cartridge is wasteful and danger- 
ous to the eyes, etc., and, owing to the rapid evaporation, it is further impossible 
to guarantee the strength of the cartridge, even in the roughest way. Kieselguhr 
and oil seem to be suitable absorbents, and oxylignit an effective blasting agent, 
though comparative tests have not been made yet. The cartridges must be used 
within, say, 15 minutes of their preparation. There is no danger, hence, from 
missing fire. But, on the other hand, it will be difficult to fire many cartridges 
simultaneously, and, strictly speaking, the cartridges should be made on the spot, 
and be in a very hard condition. That would scarcely be possible below ground ; 
the spurting liquid might break the the glasses of the hot safety lamps, and it 
remains to be investigated whether the large volumes of oxygen might not lead 
to spontaneous ignition of marsh gas or coal dust. The evaporating oxygen 
would, on the other hand, improve the air, and the blasting would not contaminate 
it. Some of these objections are very serious, especially the unreliability of the 
power of the cartridge, and the short period during which it remains active. The 
cartridge cannot, of course, be sealed, nor can the vessels in which the liquid air 
is transported. For military operations oxylignit would certainly not appear to be 
suitable. But the whole question is only in its experimental stage, and better 
methods of making cartridges could probably be divesed. — London Engineering. 



770 USE. 

LIQUID AIR AS AN EXPLOSIVE. 

Experiments which have just been made in Austria with liquid air as an 
explosive are reported to have brought forth sensational- results. The liquid air 
was mixed with a siliceous marl, making a substance which is unsusceptible to 
shock, and will only act under direct ignition. This gives it an important advan- 
tage over dynamite. (Jne-twentieth of a pint of the mixture was placed in a 
crevice in a quarry two feet deep and ignited by electricity. The effect of the 
resulting explosion is reported to have been equal to the work of twenty times the 
same quantity of dynamite. Tests were also made with the liquid air as an 
explosive of heavy ordnance, which showed that the gun was not heated and 
that the explosive will considerably increase the range of projectiles. 



LIQUID AIR AS AN EXPLOSIVE. 

Among other peculiar properties of liquid air, says Mr. A. Larsen, in a 
paper read before the Institution of Mining Engineers, it has been found that in 
combination with carbonaceous substances it forms an explosive compound, and 
numerous experiments have been made in different countries with the view of 
applying it to blasting. The first practical trials were made in a colliery in Ger- 
many about three years ago. They do not appear to have been very successful, 
and were soon abandoned. Since then trials have been made at different places, 
but the most important of these have been made, and are still being continued, 
in one of the largest explosive works on the Continent, the carbonate factory at 
Schlebusch. 

Many different mixtures were studied, both as regards explosive strength 
and safety of manipulation, while Professor Linde endeavored to turn the results 
so obtained to practical account by getting the system introduced in the Simplon 
Tunnel. One of the problems to be studied was to find a suitable carbon carrier. 
A number of these have been tried, but most of them involve a considerable 
amount of danger ; not only are they highly inflammable after being soaked with 
liquid air, but when ignited they often detonate immediately and with great 
violence. 

Very good results have lately been obtained with a mixture of equal parts 
of paraffin and of charcoal. Several modes of preparing the cartridges have been 
adopted. Either a wrapper was first filled with the carbonaceous material and 
bodily dipped in liquid air until completely soaked, or the liquid air was poured 
into the filled wrapper. The liquid air would be taken down into the mine in 
large "ammunition boxes," the latter preferably on a wheel base, and sent into the 
different working places, like ordinary empty tubs. Square-shaped wire baskets 
filled with cartridges would be taken down at the same time, placed in the liquid 



USE. 771 

in due course, and left there. By the time the boxes had arrived at the shot-firing 
points all the cartridges would be soaked full, but they would, of course, remain 
in the liquid until immediately before being placed in the shot-holes. 

A carriage 8-in. in length by 2}i-'m. in diameter, when filled with a mixture 
of kieselguhr, tar and tar oil, weighs 11^ ozs. The same absorbed 24^ ozs. of 
liquid air, thus showing a total weight of 2 lbs. 45^ ozs. The time occupied for 
fully soaking the cartridges was about 10 minutes. The life of a liquid-air cart- 
ridge is unfortunately but ephemeral when once it has been removed from its vital 
fluid. A cartridge of the above-mentioned dimensions would have to be fired 
within 15 minutes to avoid a missfire. 

A larger cartridge would, of course, have a better chance, but a thinner one 
much less. Liquid-air cartridges are best detonated with a small gun-cotton 
primer and detonator. Dynamite primers such as are used for blasting gelatine 
are useless, as they would immediately freeze. The explosive effect to be derived 
from liquid-air cartridges depends, therefore, (i) on the "freshness" of the 
liquid; (2) on the selection of carbonaceous material; and (3) on the time of 
exposure. This last is, without doubt, the most important consideration, and, 
besides, the most difficult to adapt to the requirements of practice. 

Cartridges of small diameter, such as are met with in ordinary mining, 
would appear to require quite exceptional working conditions to enable their use 
with advantage. Even cartridges of large diameters — say, 3-in. to 4-in. — require 
very quick handling. The rapid surface evaporation soon creates a coating of 
inert material around the cartridge which, acting like an empty space, causes a 
considerable loss of pressure. Again, the absorptive power of the carbon carrier, 
as well as the amount of carbon contained therein, are important factors to con- 
sider. A carrier rich in carbon, but of inferior absorbent capacity, will, if the 
cartridge be exposed too long, leave too much carbon monoxide in the fumes to 
make it safe for underground work. 

Broadly speaking, it may be said that with certain admixtures, notably of 
the petroleum variety, and by using highly-oxygenated air, it is possible to obtain 
an explosive compound of greater strength than blasting gelatine. But these 
mixtures are, as already mentioned, highly inflammable, and therefore dangerous 
to use. The safer mixtures are less strong. Owing to the rapid evaporation, 
however, a reliable standard of strength is not obtainable in any case. 



^ MICROBES THRIVE ON LIQUID AIR. 

^ At the meeting of the Royal Society, at Burlington House, a paper was read 
describing some of the results of a remarkable investigation which has been 
undertaken by Professor Dewar, Sir James Critchton- Browne, and Professor 
Macfadyen. These gentlemen have submitted a large number of disease-causing 



772 



USE. 



microbes — those responsible for typhoid fever, diphtheria, cholera and others — for 
prolonged periods to the temperature of liquid air, which is igo Centigrade, and 
have found that they are not a bit the worse. After 20 hours of this frigid regimen 
these lively bacteria proved as lively as ever, and set up with punctuality and pre- 
cision their appropriate maladies. The microbes are to have a dose of liquid 
hydrogen shortly, and it is said if they can stand that they will stand anything. 



LIQUID AIR IN MEDICINE AND SURGERY. 

Dr. A. Campbell White, writing for the Medical Record, says : 

"I think there is reason to hope that we have in liquid air a therapeutic 
agent which will remove many otherwise obstinate superficial lesions of the body 
and cure some lesions which have heretofore resisted all measures of treatment 
at our disposal, including the knife. I am firmly convinced, with the experience 
already had with its use, that it is a specific in the treatment of such diseases as 
herpes zoster (painful neuralgia, accompanied by an eruption), sciatica and inter- 
costal and facial neuralgia, affording instant and continued relief after one appli- 
cation over the spinal end of the affected nerve. The use of liquid air in medi- 
cine, i. e., in pulmonary diseases, in the reduction of fever, etc., opens a large 
field, one which presents many obstacles at the very start, but much hope for the 
future." 

Dr. White, who is known as the first New York physician to use anti-toxin, 
became interested. Mr. Tripler gave him the use of his laboratory, and Health 
Commissioner Jenkins gave him the privileges of the department's hospital lab- 
oratory to test the effects of liquid air on germ life. 

Dr. White began treatment of the human skin by curing ulcers of the leg. 
The doctor put himself on record as saying : "So many of these cases have been 
successfully treated with liquid air that it can be positively said that we have 
nothing at our disposal to-day which will cure ulcers so quickly, thoroughly and 
with as little pain." 

Dr. White accounts for the phenomenal quality of liquid air in this way: 
He says in liquid air we have pure cold without moisture. The danger in getting 
one's feet frozen is not long exposure to cold^ but to cold and moisture com- 
bined; moisture preventing evaporation. 



LIQUID AIR IN GAS MAKING. 

In the Chemische Industrie Professor W. Hempel, of Dresden, has an arti- 
cle on the use in gasmaking of the mixture of half oxygen and half nitrogen, 
which is obtained by liquefying air in a Linde machine and allowing the liquid 
air to evaporate its nitrogen partly away. The half-and-half mixture can be made 
at a working cost of 4d. per thousand cubic feet by evaporating the remaining 
liquid, and it can be applied in two ways, for making oxygen producer gas and 



P" 



USE. 773 



for making oxygen water gas. Both in producer gas and in water gas the great 
advantages of internal heating are secured; but in both cases there is too much 
nitrogen in the product, and the heating values are relatively low. 

PRODUCER GAS. 

In making this gas, as used in regenerative heating, we pass air through 

glowing coke so as to form carbonic oxide and nitrogen. But if Linde 50 per 

cent, oxygen be used the results alter considerably, in the manner illustrated by 

the following table, which refers to gas made from brown coal : 

Ordinary Oxygen 

Producer Producer Gas. 

Gas, Vol- , ' > 

umes=Per- 77ol- Per- 
centages, umea. centages. 

CO2 34 34 6.1 

Heavy hydrocarbons 0.8 0.8 1.4 

Oxygen 0.3 0.3 0.5 

CO 25.4 25.4 45-9 

CH4 5-3 5.3 10.7 

H 6.8 6.8 12.3 

N 574 12.7 23.0 

994 54.7 99-9 

These results are approximate, and would be affected by the nitrogen taken 
in along with the production of CO2 ; but, on the other hand, the production of 
CO2 would be diminished, on account of the higher temperatures which would be 
obtained in the producer. For manufacture of such a gas as that in the last col- 
umn it is only necessary to use the 50 per cent. Linde oxygen in the producer. 



COMPRESSED AIR AND LIQUID AIR AS USED IN THE SIMPLON 
TUNNEL CONSTRUCTION. 

Mr. Axel Larsen, M. Inst. M. E., in Gassier s for January, 1900, has an 
interesting article illustrating and describing the progress of work on the Simplon 
tunnel. 

Among the ordinary uses of compressed air on this work we also find 
some extraordinary uses. To clear away the debris Mr. Brandt, of the firm of 
contractors who are building the tunnel, proposes to use a gigantic air gun 300 
feet long, and with a calibre of 6J/2 inches. This gun is charged with compressed 
air at a pressure of 100 atmospheres and fires a projectile of goo gallons of water. 
When the cannon has been placed in position the powder fuses will be abandoned 
and the shot firing will be done by electricity. In this manner it will be possible 
to fire the explosive in the bore holes and gun simultaneously. Thus at the same 
moment as the solid rock is splintered into a heap of fragments by the blasting 
charges a huge volume of water is hurled against the debris which is instantane- 
ouslv washed away from the working face and left against the wall some 50 yards 
further down the tunnel. 



774 USE. 

It is at this tunnel that the use of liquid air as an explosive was first tried, 
and much is expected of it.- The cost of it is comparatively low, as liquid air 
could be made on the spot where ample water power is available. The minor 
difficulties with it have been overcome and it is now possible to keep liquid air in 
specially constructed vessels for fourteen days and longer. Cartridges of 6 inches 
diameter would have a life of over a quarter of an hour, which would be sufficient 
*or loading and firing. But one great drawback remains. It is the danger of 
premature explosion of the cartridges when accidentally brought into contact 
with fire, and as naked lights of the oldest type are used everywhere in the 
Simplon tunnel, such an accident would seem extremely probable. 

A liquid air cartridge is made as follows : A cylindrical paper or cardboard 
wrapper is filled with the powdered material intended to support combustion, 
the liquid air being, of course, the oxidizing agent. The cartridge is then bodily 
immersed in liquid air. In from 15 to 20 minutes it is soaked through and is 
ready for use. Several mixtures of carbonaceous bodies have been tried as 
substances supporting the combustion, and it has been found that not all of them 
involve the same degree of danger. Some of the cartridges made as above 
described burn away more or less violently when ignited by flame, while others 
explode almost immediately. Unfortunately, the mixtures which have proved 
comparatively safe are also the least effective. It, therefore, remains to be seen 
whether a mixture will be found which combines sufficient explosive strength 
with safety of handling. Meanwhile, it may be said with a fair degree of cer- 
tainty that liquid air mixtures will never be generally introduced as a blasting 
agent, for apart from the difficulty of preparing the cartridges under ordinary 
mining conditions, it is an exceptional thing to meet with 6^-inch cartridges in 
ordinary mining (i to 2 inches being the usual sizes), and a thinner cartridge 
does not retain the liquid air long enough to be relied upon for shot-firing pur- 
poses. 

With the work in the Simplon tunnel it is, of course, a different matter. 
The conditions there are different. It is altogether an exceptional case, and if 
the experiments with liquid air should ultimately prove successful, the advan- 
tages achieved may mean the completion of the tunnel in 1903 or even earlier. 

Professor Linde, of Munich, who has done so much to render the lique- 
faction of the atmospheric air an industrial success, personally conducts these 
experiments at his laboratory near Brig, and his thorough knowledge of the 
subject promises a successful issue, if it is to be attained at all. 



COMBUSTION IN LIQUID AIR. 



When air is liquefied, nitrogen and oxygen condense simultaneously, so that 
the liquid has the composition of the gas mixture in the air. As soon, however, as 
evaporation recommences, the composition begins to change. At first the escaping 
gas is essentially nitrogen. After a while the vapors again contain the two gases 
in the proportions in which they are found in the atmosphere. That point occurs 
when about 70 per cent, of the liquid has evaporated, and 81 per cent, of the 
original nitrogen, and 35 per cent, of the oxygen have escaped; the remaining 



USE. 775 



I. 

predominate in the vapors. These numbers concern evaporation at atmospheric 
pressure. In vacuo, the evaporation of the two gases proceeds more rapidly ; at in- 
creased pressure, more slowly. The changes may be observed with the help of a 
glowing chip of wood. At first the wood will be extinguished, when held over the 
liquid; then it will brighten up, and when dipped into the liquid burn intensely. 
Powdered carbon, soaked with liquid air, puffs away like gunpowder on ignition, 
and explodes when a detonator cap is employed. This seems very strange when 
we think of the exceedingly low temperature of the liquid, — i8o degrees C. ; and 
in a paper brought before the Bavarian Academy of Science, Carl Linde expresses 
the opinion that we may have to modify our views on the nature of explosions. 
Petroleum, absorbed by kieselguhr or powdered cork 'Coal, can be saturated with 
liquid oxygen. Such a mixture explodes even when not confined. Cartridges 
filled with it cause others, placed at a distance of 25 centimetres (10 in.) from 
them to explode, while with the highest explosive so far known, blasting gelatine, 
cartridges 15 centimetres away from the detonating cartridge remain inactive. 
Linde has tested this preparation at Schlebnoch. Within a steel bomb of 20 litres 
capacity blasting agents are exploded by means of fulminate of mercury. The gas 
pressure is registered by a piston on a drum which has a circumferential velocity 
of 330 centimetres (10 ft.) per second. The petroleum-liquid air preparation gives 
a curve which demonstrates that the maximum pressure surpasses that obtained 
with blasting gelatine, and is reached in a shorter period of time. The prepara- 
tion was simply wrapped in paper. It is singular that such a mixture should burn 
more rapidly, in spite of its low temperature, than any solid or liquid compound 
we know at ordinary temperatures. — Engineering. 



A PLANT FOR THE COMMERCIAL MANUFACTURE OF LIQUID AIR. 

The announcement that within a short time there will be in operation in 
New York City a commercial liquid air producing plant, with an estimated 
capacity of some 1,500 gallons of liquid air per day, is certainly a remarkable one, 
and especially so when it is remembered how short a time has elapsed since the 
liquefaction of air was first effected, and that up to a couple of years ago or so 
the lequefaction had only been accomplished on a minute scale in one or two 
laboratories, and at an expense which made the product almost as costly as a 
precious metal. 

In the issue of Engineering News for April 14, 1898, was given the first 
technical description of the laboratory and apparatus of Mr. Charles E. Tripler, 
of New York City, who was unquestionably the first to produce liquid air on 
anything like a commercial scale. 

Since then, descriptions of this laboratory, and statements concerning Mr. 
Tripler's work of all degrees of accuracy and inaccuracy have run the rounds of 
the newspapers and the popular magazines, so that the general public has become 
quite conversant with liquid air, at least, from the spectacular standpoint. 

In our article above referred to, and in an editorial discussion of the possi- 
bilities of liquid air, published in the same issue, some of the uses and the limita- 



776 



USE. 



tions of liquid air were pointed out. These prospective uses and the great 
popular interest in the subject, have set a large number of investors and scientists 
at work in this field, both in this country and abroad. 

By all odds, the most extensive work, hov»>ever, to the best of our knowl- 
edge, has been done by the General Liquid Air & Refrigerating Co., of New 
York City, whose offices are in the same building as those of Engineering News. 
This company has been organized to control the inventions of Messrs. O. P. 
Ostergren and Moriz Burger, relating to the liquefaction of air. It has secured 



3^ 
/nfer- 
cooier 




To Outside 



Steam 
Cylindei 



a 



w^^^?#^' 



I cooler 



Inter- 
cooler 



Q 



\5tearn 
Cytinde'' 




Boilers 



FIG. 283— SKETCH DIAGRAM OF AIR WOUEFVING PI.ANT, SHOWING PRINCIPAIv ; 

APPARATUS AND PIPING. 



patents in the United States, and in a large number of foreign countries, and it 
has built and has now ready for operation a plant for the commercial production 
of liquid air on a scale sufficiently large to demonstrate the efficiency and value 
of its process. 

In the accompanying diagram, Fig. 283, we have represented in symbol the 
various parts of the apparatus, and by reference to this, the operation of the 
plant will be readily made clear to the reader. It may be said in the first place 
that in principle the plant is merely a steam-power refrigerating plant, utilizing 
the expansion of compressed air to produce a low temperature, and causing this 



r 



USE. 777 



cold air to react upon itself, utilizing a different principle, as they claim, from 
that of the Tripler or the Hampson apparatus, until a temperature is reached so 
low that liquefaction occurs. 

The steam is furnished by three vertical fire tube boilers, of 75 nominal 
H. P. each. These deliver steam at 150 lbs. pressure to two independent, two- 
stage horizontal straight line air compressors, built by the Ingersoll-Sergeant 
Drill Co., of New York City. The one at the left, which may properly be termed 
the low-pressure compressor, has a 16 x i8-in. steam cylinder, an i8^-in. low 
pressure cylinder, and a 12-in. intermediate air cylinder. These are connected 
by the first intercooler. The large low pressure cylinder is in reality a vacuum 
cylinder, whose function will be explained later, and m this the maximum pres- 
sure is never more than the atmosphere, or 15 lbs. The air leaves the second 
cylinder at 60 lbs., gauge pressure, and passes through the second intercooler to 
the low pressure cylinder of the second or righthand compressor. This has a 
22 X 24-in. steam C3'linder, low and high pressure cylinders 7^ and 7 ins., 
respectively, in dia;neter. 

The third compressing cylinder delivers the air into the third intercooler 
at a pressure of 300 lbs., and from it the air enters the high pressure cylinder and 
is raised to 1,200 lbs. pressure. The air then passes to the aftercooler. In this, 
as well as in the intercoolers, the operation is simply to extract the heat which 
has been generated by the compression of the air b}-- passing the air over water- 
cooled tubes. 

So far, the operation is identical with that of any ordinary four-stage air 
compressing plant. It is from this point on that the special apparatus for puri- 
fying and refrigerating the compressed air comes into play. Continuing the 
circuit from the aftercooler, the air enters at the base of a tall separator, 
whose purpose is to remove all moisture, oil, dust or other impurities from the 
compressed air, an operation quite essential to prevent the liquefier becoming 
clogged with ice and grease. As it enters the separator the compressed air meets 
a perforated disc, which breaks the incoming current up into a large number of 
fine jets. These bubble up through a column of water which washes the air and 
extracts from it all grease or other impurities which it may have accumulated 

• in its journey through the compressors, intercoolers and piping. Breaking from 
the water surface, the level of which can be maintained by means of the blow-off 
or regulating pipe, the air rises towards the top of the separator and strikes a 
series of conical baffle plates, between which it zig-zags, as shown by the arrows, 
until the top of the separator is reached. It will be noticed that the alternate 

■ plates with open tops have a series of holes in the inner casing which supports 
all the plates. This arrangement permits the entrained moisture to run back to 
the water chamber without coming into contact with the rising current of air. 

Just beyond the outlet end of the separator is a pressure regulating valve, 
whose duty is to let the compressed air pass by at a constant pressure, so that it 
will enter the liquefier in a constant and steady stream. From the far side of this 
valve a small pipe is carried to the automatic governor of the steam end of the 
high pressure compressor to insure its proper action. 

Passing on the air enters the header of the brine or cooling tank, Fig. 284. 
The header has an inner tube, which is small enough to considerably increase 
the velocity of the entering air, and at its lower end is provided with a small 



778 



USE. 



inverted conical, nozzle-closing receptacle, known as the "supplementary moisture 
collector." The air passing through the small tube, with increased velocity pro- 
jects into the nozzle any moisture which may have passed the separator, and then 
passes up between the small tube and the header. Radiating from this header 
and winding spirally inward towards the centre of the tank, Fig. 285, is a series of 
flat coils, all of which terminate in a second header, from which the air pipe leads 
to the liquefier. Beginning at the centre of the tank and winding outward in the 
reverse direction, is a similar and duplicate set of spiral tubes which terminate 
in an outside header. This second set contain the expanded air returning from 
the liquefier. The principle of this apparatus is seen by referring to Fig. 285, in 
which it will be seen that the cold expanded air in passing through its coils is in 
close proximity to the entering compressed and warm air. 

Before considering the liquefier it is perhaps well to trace the course of 
what has just been called the expanded air. In reality, this is only partially ex- 




X = Ejipancied Air 

Exit 
6= Enpandeai Ai' 

Entrance 

CimC news. 



CompresiedAie 
Exit. 
£,= Compressed AJ^ 
Entrance 



FIG. 284 — PLAN OF THE BRINE TANK, SHOWING ONE LAYER OF COILS. 



panded, for it reaches the exit end of the brine tank coil at a pressure of about 
300 lbs. per square inch. Referring again to Fig. 283 it will be noticed that a pipe 
leads to the third intercooler, which has also a pressure of 300 lbs. This ar- 
rangement, it will be observed, starts the cleaned and cooled air which has not 
been liquefied on the circuit again at a point where only a single compression is 
necessary to put it into condition for supplying to the liquefier. 

The principal part of the system and, of course, the one to which the most 
interest attaches, is this liquefier. For the present let us consider the apparatus 
without air, as it stands when inoperative. 

The liquefier consists of two portions. Fig. 286, the upper and larger of the 
liquefier proper, and the smaller and lower portion called the aftercooler which 



USE. 



779 



contains the reservoir for the liquid air and plays a very important part in the 
proper working of the system. 

Referring now to the liquefier, the upper portion is filled with two 
sets of coils of small copper pipes which, as in the case of the brine tank^ 
are wound in flat spirals in reverse directions, that is, those for the entering 
air spirally inward to the central of the header, shown in Fig. 286, and 
the other set starting from the outer section of the breaker and spiralling 
outward to an outside header. However, a fundamental difference exists between 
the brine tank and the liquefier in the fact that the tubes of the latter are soldered 



Lr,in' 



Vl^ffvf 



' I- 



<3^ 



Lake 






I No.ibbahlrv 

C cieanieaAir toPtts- . 

jure Regulating *&/>* 



?'0' 



Coke 



worer 



K •- 3' 



....... Bm"" 



? -^ 



Nolbbaiv.iron 



No 16 Pertvnmd 



n.i''''i' 



FIG. 285 — SECTION OF THE CLEANSER FOR REMOVING DUST FROm' AII^ PREVlduS TO 

COMPRESSION. ' ' - 



together in vertical rows, thus forming a spiral space from the outside to the 
'inside, or vice versa. In other words, it is as if a solid flat strip of 40 tubes were 
wound in a spiral. Connected with the space which surrounds both sets of 
tubes is a large exhaust pipe leading to the suction end of the first cylinder of the 
low pressure compressor, already mentioned, whose function it is to exhaust the 
air from this space and the interior of the aftercooler, as will be explained later. 

tThe aftercooler, shown in detail in Fig. 286, consists of a central chamber 
ed by a heavy cast-iron inverted cup, resting on a knife-edge turned on the 
of the reservoir, and a siphon tube dipping to the bottom of the reservoir, 
and winding around the cup and cover, and finally emerging to the outside of 
the supporting casing of the apparatus. This is all enclosed in an air-tight cas- 



I 



78o USE. 

ing which connected to the spiral space of the liquefier, and hence to the vacuum 
pump. 

At the lower extremity of the central header of the liquefier, and at the top 
of the aftercooler, are two similar valves, shown in detail in Fig. 286, and operated 
by separate valve handles from the outside of the apparatus. 

Having now an idea of the mechanical construction of the apparatus, let us 
start with the compressed air entering the liquefier, and follow the operation of 
the several parts. The air, at a pressure of about 1,200 lbs., and a temperature 
equal to that of the brine tank, say 50 or 60° F., flows into the outside header, 
and round and round through the spiral tubes towards the central chamber, and 
finally through the expansion valve into the small space below. This valve is so 
adjusted as to throttle the flow and keep the difference of pressure between the 
two sides of the valve at approximately 900 lbs. This drop in pressure, and con- 
sequent expansion cools the air a certain amount. This cooled air now passes 
upward in the outer portion of the central header and starts in its spiral course 
outward, the tubes in which it is confined being in close metallic contact with the 
entering air tubes. No matter how small the difference in temperature may be, 
the entering air will in consequence lose some of its heat to the outgoing cooler 
air, and will thus arrive at the expansion valve at a slightly reduced temperature 
only to expand and produce a further drop in temperature, which, in its turn, 
still further cools the entering air. This accumulative cooling continues until 
eventually the critical temperature of air is reached. Then, and then only, 
a portion of the air passing through the expansion valve liquefies and collects 
the small chamber over the second or aftercooler or reservoir valve. That por 
tion which does not liquefy, which is, however, intensely cold, of course passes 
into the cooling tubes as before. 

From what has been said, it will be seen that the air once taken into the 
system is used over and over. There is, of course, need for new air to take the 
place of that liquefied, and this is drawn in from outside through the cleanser, 
shown in Fig. 285, and a suitable automatic valve. This cleanser consists of an 
inlet tube coming from the roof of the building, and extending down to the 
bottom of the containing tank. From the bottom of the four arms, the air bub- 
bles out and up through water to a coke filter, where it is thoroughly scrubbed. 
It is also subjected to a water spra}^, after which it remains in the upper portion 
of the tank until needed by the system, when it is drawn into the vacuum 
cylinder. 

Returning to the liquefier again, it will be seen that opening the after- 
cooler valve allows the liquid air to pass into the reservoir below, where at first 
it will immediately volatilize, owing to this portion of the apparatus being warm. 
This will produce in the reservoir sufficient pressure to lift the heavy inverted 
cup and permit the intensely cold air to flow out into the vacuum space of the 
aftercooler, and thence through the spiral space of the liquefier. At the same 
time a portion of the cold air will pass through the coiled siphon tube and out the 
draw-off valve. Soon the parts of the aftercooler become sufficiently chilled, and 
the liquid air passing through the lower valve, remains in a liquid state. The 
heavy cap is so proportioned that there is a pressure of about 6 lbs. per sq. in. on 



T- I 



i 



USE. 



781 



the liquid surface, and this is sufficient to force the liquid air through the siphon 
tube and out of the faucet. We then have the following condition of affairs : 

The reservoir is partially filled with liquid air, as is also the coils of the 
aftercooler, and the space surrounding the tubes is constantly being exhausted, so 
that whatever liquid air or vapor may spill over when the inverted cap lifts is 
instantly evaporated in and around these filled tubes, thus further reducing the 




ReMrvoir Valve 
Enlorged . 

FIG. 286 — SECTIONAL ELEVATIOT»J OF LIQUEFIER AND AFTERCOOLER, SHOWING DETAILS OF 

VALVES. LIQUEFIER COILS ARE NOT SHOWN. 



782 USE. 

temperature of the air about to be drawn off; the vacuum spiral space surround- 
ing the tubes of the liquefier is constantly having the intensely cold evaporated 
air passing through it and the temperature of the whole apparatus is therefore 
being gradually reduced toward some minimum which, so far as present indica- 
tions go, is remarkably near absolute zero. In fact, judging from results ob- 
tained the first time the plant was operated to test the compressors, etc., it may 
be expected that air will be actually solidified. 

The same test seemed to indicate that the brine tank is superfluous, and 
it was found that the entering and leaving air and the liquefier casing were at 
practically the same temperature. 

One of the problems to be solved before liquid air can be of any great 
commercial value is some method of carrying and storing the material so that it 
can be retained in a liquid form. The company has endeavored to perfect this 
feature in a practical and business-like way. The results of its efforts 
is a double tank consisting of an outer and inner tank. The inner 
metal vessel is closed, except for a small offset pressure gauge tube, 
and the larger opening constituting at the same time the filling tube 
and the relief valve. Surrounding this is a second vessel, in its turn 
surrounded by some non-conducting material such as corn pith, excelsior, 
granulated cork or the like, contained in a wicker basket. The inner tank being 
filled with liquid air the relief valve automatically opens slightly from time to 
time, as the pressure exceeds about 6 lbs., and permits the escape of the cold 
air into the space between the two metallic tanks. This forces the warmer air 
out through the bottom of the tank and maintains a very cold blanket of air be- 
tween the liquid air and the exterior insulating casing ; smaller and cheaper forms 
are made by using an open inner vessel made of wood pulp similar to the well- 
known one-piece water buckets. These are surrounded by wire netting held 
away by small wooden strips. 

The vessel is then put in a wicker basket, packed about with some insulat- 
ing material as in the former case, and is provided with a wooden cover which 
rests on the wire netting and forms an air space. 

Still another form consists of two metallic spheres, between which is a 
third molded cork sphere held away from the others. 

Both the inner and outer spheres are provided with separate relief valves, 
so that when the pressure exceeds a certain set amount the inner valve lifts and, 
one might say, exhales into the space between the inner and the cork spheres. 
The cold air gradually works outward through the cork, becoming warmer as it 
progresses. Finally it reaches the space between the cork shell and the outer 
metal casing and accumulates until the pressure is sufficient to lift the second 
valve when it passes into the surrounding atmosphere. 

While the company has devoted its chief endeavors to the process of 
liquid air manufacture and transportation, it has also paid some attention to the 
possible applications cf liquid air. One which is of especial interest in these 
summer days is the operation of a cooling fan by compressed air obtained from 
volatilizing liquid air. The liquid is held in a suitable receptacle, while a coil 
connected with this receptacle constitutes a vaporizer and heater utilizing the 
heat of the atmosphere. The fan is revolved by a small turbine driven by the air 
imder pressure, which, as it escapes from the motor, is caught by the fan blades 



r 



USE. 783 



and whirled forward in the current of air. In this way not only is the air in a 
room kept in constant motion, but it is continually cooled and freshened by the 
addition of the cold exhaust air of the motor. 

To our readers who have followed the above description of the air liquefy- 
ing process, it will be apparent that its efficiency, or the quantity of liquid air 
produced for a given expenditure of power, depends primarily upon the amount 
of refrigeration which is effected in the expansion of the air through the con- 
tracted orifice of the expansion valve from a pressure of 1,200 lbs. to a pressure 
of 300 lbs. The cooling which is effected in such an expansion from ordinary 
atmospheric temperatures, when the expansion takes place in a cylinder against 
a piston, is, of course, known with fair accuracy; but what the cooling may be 
when the expansion occurs through a nozzle and the jet of air at high velocity, 
performs more or less internal work which tends to restore its "original heat, is 
something as yet unknown, and which can only be determined by careful experi- 
ment. 

Such preliminary tests as have been made with the above apparatus, how- 
ever, indicate that the refrigeration due to the expansion under the conditions 
existing in this apparatus, is much greater than such empirical formulas as have 
been heretofore relied upon have indicated. The results of complete and accu- 
rate tests to determine the product of liquid air per horse-power hour in this 
apparatus, will therefore be awaited with interest. 

For the material from which this description and the accompanying illus- 
trations have been prepared, we are indebted to Messrs, O. P. Ostergren, Presi- 
dent and Engineer of the General Liquid Air Co., and S. M. Gardenhire, Esq., 
its Secretary. — Engineering News. 



MECHANICAL APPLICATION OF COMPRESSED AIR. 

We have had this week a significant illustration of the scientific interest 
which is taken in the utilization of this force. There is, perhaps, no institute in 
the United States which has more speedily recognized new commercial tendencies 
and utilizations due to scientific discovery than the Franklin Institute of Phila- 
delphia. This institution set apart one evening recently for the discussion of the 
various uses to which compressed air is now put for commercial ends and for a 
discussion as to the range in the future which the utilization of this force may find 
in commerce and in manufacturing. Men of high scientific authority of New 
York, Chicago, Philadelphia and other centers in scientific study, took part in this 
discussion. 

USE IN MINOR INDUSTRIES. 

There was agreement that for a thousand and one industries, many of them 
of delicate and intricate character, compressed air is to furnish the most satis- 
factory and economical of all power-producing agents. In fact, it seems to cover 
the whole range of minor industrial vocations, especially some that hitherto have 
been presumed to be adapted only to hand power. When, the other day, workmen 
painted the whole substructure of the Washington Bridge by means of com- 



784 USE. 

pressed air apparatus and did it satisfactorily, there was amazement expressed 
here that this force could be put to such use. 

The master mechanic of the Erie Railroad laughed contemptuously when 
he was told that an air apparatus would tamp his railroad tracks more speedily 
and more cheaply than it could be done by hand power. This is something which 
master mechanics have always believed no apparatus excepting the tamping iron 
and the brawny arms of the laborer could satisfactorily do. Now, the president 
of the Erie tells his friends that compressed air apparatus will do this better than 
hand power. These are only illustrations of the wide range of the mechanical 
use mentioned at the Franklin Institute meeting. It was also said that com- 
pressed air would solve the problem of perfect food refrigeration in the tropics, 
and it is hinted that before very long there are to be established not only in 
Cuba and in Porto Rico, but in Manila, American apparatus designed to do 
this work. 

No one believes that compressed air is to be such a competitor of electric 
current as to supplant that. There are many things that electricity can do 
cheaper and better than any compressed air apparatus yet invented is able to do. 
It is more likely to supplement the electric current. 

It is true that compressed air force may be seriously threatened, by and by, 
by liquid air, the possibilities in which seem to be so great as to suggest complete 
revolution in the production and utilization of power. But that day is remote, 
although Mr. Tripler has demonstrated to the scientists of authority here that 
he is no quack, no maker of ingenious, interesting, but commercially useless phil- 
osophical experiments, but is carrying on a line of investigation worthy of the 
approval and encouragement of all scientists and of the commercial world as well. 

From 1881 to the present day we were in what may be called the era of the 
commercial development of electricity for other than telegraphic purposes. This 
year we seem to be entering into an era to be characterized by the commercial 
utilization of compressed air, not so much in competition with electricity, but in 
sympathy with and supplemental to it. — "Holland," in the Philadelphia Press. 



COMPRESSED AIR IN MACHINE SHOPS AND FOUNDRIES. 

In Gassier' s Magazine for August, 1895, Mr. C. O. Pleggem writes in- 
structively on the utility of compressed air for the transmission of power to out- 
of-the-way places and for use in lifts and hoists in machine shops, and also 
describes the various machines that are operated by air power. 

In machine shops compressed air serves as a helper for the machine hand 
in a far more efficient and economical manner than that rendered by the manual 
help, which in some shops require an order from the foreman and a great deal 
of time lost. 

All the attendant annoyances may be overcome by putting in air lifts over 
all lathes above 20 inches swing and over all planers, shapers, drilling machines, 
and drill presses working on pieces too heavy for one man to lift, and so quick 
and satisfactory are they in their action as to leave out of comparison all chain 



USE. 785 

blocks or chain rigs of any kind. A very cheap form of air lift is a plain cylin- 
der, suspended from a trolley traveling on a swinging arm, the cylinder being 
about four feet long, and for all lathes below 36 inch swing, or planers 30x30 
inches, it need not be more than 6 inches in diameter, and yet will lift about 2,000 
pounds with an air pressure of 80 pounds per square inch. 

Chucks, face plates and steady rests can be lifted from the floor and placed 
in position by the aid of the compressed air hoist in less time than by hand, and 
work can be lifted and placed against the face plate or in the chuck with more 
satisfaction and in less time than by any manner of "blocking up" in vogue with 
the old helper system. 

Very convenient little presses can be fixed up for driving mandrels, press- 
ing in seats for valves, linings in piston rod glands, etc. The presses are made 
with a cylinder 16 inches in diameter, which at 80 pounds pressure is equal to 
about 16,000 pounds pressure on the ram. This compressed air press will at once 
commend itself for accuracy and avoidance of many accidents. 

In turning soft steel shafting it is customary to use water to which a cer- 
tain percentage of sal soda has been added in order that the water may not rust 
the finished w(3rk. 

As the tool is being crowded away it crowds more over the harder portion 
of the steel than softer ones, and the result is, in addition to a tapering shaft one 
is also produced that is not round. 

By using a small air jet — that is, air issuing from an orifice of about 1-16 
inch in diameter, the work can be finished very much the same as if water is 
used. A smooth surface will be produced with this important difference, that the 
tool will not crowd, and, consequently, the shaft will be nearer true and straight 
when using compressed air than when using water. 

The same size of air jet may be used to advantage at different places 
around the shop. It is excellent for cleaning off benches and machines, and is 
much to be preferred to the common dust brush for this purpose. 

Punching may be done by having a small cylinder at the back end or arm, 
suitably pivoted, at the other end of which the attachment is made to the head 
carrying the punch. Such an arrangement is especially well adapted for quick 
work in the construction of smokestacks, breechings, tanks, and all work not re- 
quiring heavier than % inch, or, say. No. 8 gauge of iron or steel. With these 
presses arranged so as to be operated by a foot tripping device and equipped 
with jigs, it is surprising how much more can be done than by any other system 
^ laying out. 

B A number of special tools have been on the market for some time, made 
^r compressed air caulking. Some of these tools do the Work very effectively, 
and with a minimum amount of discomfort to the man running it, in the shape 
of reduced jar. 

It is an incontrovertible fact that caulking is done better and can be done 
^fcry much cheaper by air pressure than by hand. 

^ From the machine shop and boiler shop Mr. Heggem goes to the foundry. 
and there on every side he hears the blasts of escaping air. Here are direct lifts 
or suspended cylinders of five tons capacity. Copes are lifted off without any 
jar. Patterns are lifted out just as slowly as you please until they are clear of 



L 



786 USE. 

the mould. Large green cores are placed in position to dry, without jar or shock 
of any kind. 

Compressed air for lifting and other purposes in the foundry will com- 
mend itself to any practical foundryman without using any argument whatever 
in its favor. 

In the same article the writer gives practical advice to those contemplating 
compressed air. He says : "Put in a compressor two or three times as large 
as you think you will actually need, and a belted compressor is to be preferred 
to a steam-driven one where the main engine running the shop machinery is 
sufficiently large to carry this addition. It is preferable because it is more 
economically run, no matter from what standpoint the economy is viewed." 



IN AND ABOUT RAILROAD MACHINE SHOPS. 

The sand blast is the most efficient means of cleaning paint scale and rust 
from tanks. No other way cleans out the pitting and around the rivets as satis- 
factorily. 

A tender which had been repainted several times can be cleaned bright at 
the rate of a square foot in 7 minutes. A tank which had never been painted 
may be cleaned of rust at the rate of a square foot in 3 minutes. 

At the Susquehanna, Pa., shops of the Erie R. R. Co., a Baird stay-bolt 
breaker saves 50 per cent, in time and one man at $1.40 per day. Two men and 
the pneumatic breaker can break 300 to 325 stay-bolts in 7 hours. 

Stay-bolt tapper run by air saves 50 per cent. 

Stay-bolt pincher or cutter operated by 2 men cuts 1,000 per hour on inside 
work. By hand one man can cut 300 in 4 hours. 

Caulking and beading tool beads 235 2-inch flues in two hours and ten 
minutes. By hand 200 flues can be beaded in ten hours. 

Mud ring riveter and two helpers at $1.40 per day each will do as much 
as two boiler makers at $2.30 per day each and one helper used to do in two days. 

Riveting bull saves one man's time at $1.40. Bull also used to punch out 
old stay bolts after same have been cut. One boiler maker at $2.30 per day by j 
hand can punch out 100 per day. Bull and two helpers at $1.40 each punches 300 
in five hours. 

Tank frame pneumatic riveter operated at 100 pounds pressure saves 50 
per cent. Flue swageing machine for reducing flue end 1-16 inch for ferrule 
saves 50 per cent, in time. 

At the establishment of Russell & Co., Massillon, Ohio, oil stored in tanks 
buried in the ground is forced by air pressure to store room where it is drawn 
from a faucet as required. This is a great convenience and minimizes the fire risk. 

Stay-bolt cutter cuts 100 ^'4-inch bolts in one-half hour, by hand lOO to 
two hours is the average. When stay-bolt cutter was introduced a reduction of 
60 per cent, was made in the pay of men doing this work and still they now make 
6 per cent, more wages than before the reduction. 

The cutter does not loosen the stay like chipping by hand is likely to do. 



USE. 
MANHATTAN ELEVATED RAILROAD SHOPS. 



787 



The power which is extending its range in railroad fields with a force and 
vigor of which we have no recorded precedent, is compressed air, which is becom- 
ing every day more and more closely linked with practical usefulness, and the 
reason therefor is not far to seek, and is a short tale soon told. 

Compressed air and pneumatic apparatus of the highest types, are the em- 
bodiments of inventions made by mechanicians who grasped the compressed air 
proposition with one hand, and the requirements of industries with the other, 
incorporating them into the moulds that fashioned the compressors and tools 




FIG. 287 — BORING HOLES IN WOOD. 



which are at work to-day in every part of the world. One of the most con- 
spicuous features in the progress of compressed air apparatus and pneumatic 
tools is their rapidly extended use in railroad shops, under numerous novel condi- 
tions and forms. A notably well conceived and carried out installation of the 
latest type of compressed air service is that in the shops of the Manhattan 
Elevated Railroad Company, which covers two city blocks in the Borough of 

^lanhattan, bounded by East 98th and 99th Streets and Third and Fourth 

■iLvenues. 

*^ The elevated roads comprised under the Manhattan management have been, 

for a quarter of a century, a great factor in the upbuilding of the new west and 



788 USE. 

east sides of what are now the Boroughs of Manhattan and Bronx. In 1873, the 
then existing elevated road was a light structure, single track with sidings, 
extending from Rector to West 34th Street. The power was transmitted from 
stationary engines, to endless chains clutched by the cars. The system was crude, 
when measured from the standpoint of to-day, but nevertheless, the road sprang 
into immediate popularity, and its prosperity led to the great extension com- 
menced in 1876, which stretched miles of tracks over territory in great part 
devoted to agriculture, and as sparsely settled as counties of the State bordering 
upon the Adirondack region. It is now 20 years since the roads were completed to 




FIG. 288 — BORING OUT A CYLINDER. 



the Harlem river and beyond, and the strongest evidence of the road's success in 
building up the city is the indisputable evidence that since 1876, there has been 
built upon land from 59th Street to 176th Street, and from river to river, homes, 
shops, factories and institutions which house a larger population than is enumer- 
ated in the combined populations of Boston and Baltimore. 

The Manhattan elevated system holds the world's record for frequency of 
trains, and passenger traffic, per mile of track. As an illustration of the volume 
of traffic, it may be said, that the system conveys more passengers than all the 
railroads which ply between the Potomac and Rio Grande rivers. 



USE. 789 

The following figures show the enormous traffic of one year. 

Train, Car and Engine Mileage and Passengers Carried, Fiscal Year ending June 30th, 1867. 

Train Miles. Car Miles. Eng. Miles. 

Branches 120,130.78 184,558.30 120,130.78 

Main Lines 9,790,834.60 42,996,973.42 10,548,448.28 

Total 9.910,965.38 43,181,531.78 10,668,579.06 

Total number of Passengers— All lines 182,964,851 

The need of improved appliances suitable for handling expeditiously the 
vast equipment of the road was quickly appreciated by Mr. W. J. Fransioli, 




FIG. 289 — CHIPPING AND DRILLING WITH HAESELER DRILLS AND BOYER TOOLS. 



General Manager of the Manhattan Elevated Railroad, and one of his earliest 
acts on assuming management was to take up the compressed air feature. Previ- 
ous to that time it had not been used at all. By his kind permission we recently 
had the pleasure of visiting the Manhattan shops for the purpose shown herein. 

For the information relative to the plant we are indebted to Mr. M. Mc- 
Nally, Master Mechanic. 



-I 



790 



USE. 



The air compressor is situated in the boiler and engine room, a separate 
building, adjacent to the blacksmith, boiler and machine shops. The type is an 
IngersoU-Sergeant. 

From the reservoir the air is conveyed in 600 feet of three inch, and 900 
feet of two inch mains, to the various shops. In one line of main pipe the exten- 
sion is underground in a public street, and then overhead for distribution in a shop 
400 feet from the compressor, but there is no drop in potentialty in any of the 
smaller supply pipes deflected from that main. In each shop there are either bat- 
teries or single air tanks conveniently placed for access and distribution to the best 
advantage. A great many air hoists are used, and one is in course of construction 




FIG. 290 GAUGE TESTING APPARATUS. 



for hoisting lumber from the yard to the upper stories of the wood working shops, 
which will hoist about 3,000 pounds or less, 26 feet. 

Several pneumatic cranes are in use; one recently installed, enables one 
man in one minute, to perform work that formerly required two men four 
minutes. In the boiler shop pneumatic tapping, screwing and drilling machines, 
perform varied operations with high velocity and accuracy. In form the machine 
is a rotary miniature engine, with a short cylinder fitted with a circular piston, 
internaUy tangent to the cylinder; the axis of the piston being parallel with the 
cylinder. A sliding diaphragm of brass divides the cylinder into two equal 
parts, air admitted behind the diaphragm, causes it to revolve until the exhaust 
passage is reached. The speed of the piston is controlled by gearing. This 
ingenious machine is used for tapping and screwing staybolts, reaming and drill- 



USE. 



791 



ing out boiler tubes, and drilling of several descriptions. With this machine a 
good mechanic can roll out 200 boiler tubes on both ends in four hours. 

Several riveters are in use, and in them is noticeable the striking superi- 
ority of pneumatic over hydraulic riveters, in that the pneumatic riveter makes 
an initial stroke that is quick and powerful, bonding the rivet and plate into 
homogeneity, following with a secondary blow which upsets the rivet, so that the 
rivet and orifice are fixed in a perfect unit. The pneumatic staybolt cutter has a 
capacity for cutting off from 1,200 to 1,500 staybolts an hour, according to the 
diameter of the bolts. 

Under the chisel and hammer method which obtains in shops not equipped 
with compressed air, staybolts are invariably loosened in the sheets, whereas with 
pneumatic tools, the work is flawless. All caulking performed in this establish- 
ment is done with pneumatic tools of especial design for the requirements. 

Reboring of Cylinders while in Shop for Ordinary Purposes. 
The hoists for axle lathes and wheel borers are also of designs adapted to 
the requirements of the work, and are provided with ingeniously constructed grip- 




FIG. 291 — cleaning rattan CAR SEATS. 



ping, and overhead trolley attachment. One man can lift a wheel to the lathe in 
two seconds. All the air hoists were made in the establishment; the material 
being wrought iron pipe, the ends being set with ordinary caps and couplings. 
The pistons work well, notwithstanding the fact, that in several patterns, the cylin- 
ders were not bored out, as is done with hydraulic jacks and hoists, and arrange- 
ments are being made for a further extension of work in tbg direction of ham- 
mers, jacks and portable cranes for use in the yards. All cylinders are blown out 
with air, replacing the steam process, so hot and uncomfortable for the hands. 
All air is delivered at uniform pressure of eighty pounds, wheresoever required 
in and out of shops. Other uses besides the foregoing are seen in the air brake 
bonding and testing processes, the testing of Pintsch gas tanks and pipes to 
eighteen atmospheres, the boring and cutting of wood, the mixing of paints, and 
the conveyance of sawdust from the shops through pipes to the sawdust furnace 
near the boiler house. 



792 USE. 

All the seats and backs of the car seats are of cane work, and are soon 
soiled and begrimed with smut and dust in the almost incessant use to which 
they are subjected. These are cleansed from dirt and dust wholly by means 
of compressed air admitted through an %" nozzle secured to flexible connections. 

All castings are cleansed by substantially the same process. A short time 
ago, when preparations were being made for painting the interior of the shops, 
Mr. McNally decided to free the walls and ceilings from dust by the use of 
compressed air forced through %'' nozzles secured to hose connections. The 
result of the operations has firmly established the process for future use. This 
iji brief recounts the application of compressed air and pneumatic tools in an 
extensive plant, which in every respect ^s in alignment with every progressive 
movement in mechanic arts that is founded upon correct principles, having for 
its purpose the production, conservation and practical use of the highest available 
type of power applied through the best tools. 

Ere long further additions will be made to the use of compressed air appa- 
ratus at this plant, where it is recognized as a mighty power, swift and sure, 
pulsating with energy that can both push and pull. 



IN THE SHOPS. 



Boiler and Firebox-Sheet and Staybolt Work at the Union Pacific Shops. 

The boiler shop is one of the most interesting departments of the manufacturing 
and repair plant of the Union Pacific at Omaha, and, as usual, the firebox work 
embraces some of the best features of this department. It is perhaps unnecessary 
to say that compressed air is used to a very great extent. With the air plant 
installed and in operation in such a variety of operations, it is difficult to imagine 
the possibility of a substitution of power or of accomplishing the work without 
its assistance with any degree of economy. 

All firebox ends of boilers are made from sheets as large as can be obtained 
from the manufacturers; that is to say, sheets are never spliced when single 
sheets of sufficient size can be obtained. The largest now used are for the firebox 
boiler sheets, and the sizes are 109^ by 235^ inches and 114 by 176 inches for 
different classes of boilers. The work to be done is laid out on the flat sheets 
before bending, and the punching for staybolts, rivets, etc., is done upon the press 
shown in an accompanying illustration. The press is a home-made affair, located 
out of doors. It is J^uilt up of columns firmly anchored in the ground and braced, 
and the thrust is taken by heavy I-beams secured to the top of the columns. The 
"anvil" is a part of a driving axle supported by a driving wheel centre as a base. 
The opening between the uprights is about 12 feet. The sheets are handled dur- 
ing the punching process by a crane, also partially shown in the illustration. This 
punch is operated wholly by air. After punching, the sheets are bant to shape in 
ordinary bending rolls. 

An ingenious device is used for holding firebox ends while flanging. The 
bed consists of a thick cast-iron plate of the form which the inside of the sheet is 



USE. 



793 



to be after flanging. This is supported near the ground level of the shop. Above 
this is a plate of similar shape, but smaller, which is attached to the piston of a 
long air cylinder anchored above. The sheet being laid upon this base, the upper 
plate is brought down and held by the air pressure while the flanging is done with 
hammers. The pressure is sufficient to hold the plate firmly in place, the base 
plate serves as a former to give an accurate curvature, and the piston rod being in 
the middle of the plate is entirely out of the way of the workmen. 

The staybolt practice in this department is an especially interesting feature 
of the work. The holes are tapped by the use of an air-operated tool, and the 




FIG. 292 — PUNCH FOR LARGE BOILER SHEETS. 



staybolts are screwed in in the same manner. All staybolts are screwed in from 
the inside and cut off inside. To do away with the necessity of forming a square 
head upon each staybolt, an ingenious and simple tool has been devised. This is 
shown in two forms in one of the accompanying engravings, one in a form adapted 
for handwork and the other the chuck which is used with the air engines. The 
clutch consists simply of a disc having an opening to receive the end of a bolt 
eccentrically mounted upon a pin, which is cut away so as to form about one- 
fourth the wall of the opening. The pin forms the means of attachment to the 
engine or to the handle when used in hand work. It is clear that the turning of 
the pin in the disc will cause the edges of the part of the pin forming the walls of 



794 USE. 

the opening to grip the bolt firmly between itself and the other wall of the open- 
ing and the result is the same in whichever direction the tool is turned. It is 
said that the threads of the bolt are not injured by the use of the tool, and the 
saving of the work of forming a square end is an obvious economy. 

It is the practice of the Union Pacific to drill all staybolts for i^ inches 
from the outer end, as a precautionary measure to secure a sure indication of bolts 
partially broken near the outer sheet. The work is done before the bolts are 
inserted, contrary to the practice in many shops. This method is made possible by 
the practice before mentioned of screwing in and cutting off staybolts on the inside 
of the firebox, since if it was necessary to cut them off outside, the drilled holes 
would be partially or wholly closed in the process of cutting. A special machine 
has been designed for the purpose of drilling, which is substantially automatic 
except in so far as it is necessary to turn air off and on. A general view of this 
machine is shown herewith. Both ends are the same as the one shown, the 
machine being fitted up double, though the work at present requires the work of 
one part of the machine and one man only. The air is regulated by the handles 
at the front of the machine. In operation, the bolt to be drilled is automatically 
gripped and presented to the drill, withdrawn at intervals to clear the drill, while 
constantly fed at a uniform rate. When the gauge indicating the proper depth of 
hole is reached, the bolt is withdrawn from the drill and automatically released 
from the clutches. Each of the two cylinders shown represents a separate working 
part of the machine, three hand levers being necessary for controlling the opera- 
tions of each cylinder. The rate of drilling is about 140 staybolts per hour, one 
man operating two drills. — Raihvay Age. 



PNEUMATIC EQUIPMENT FOR BOILER SHOPS. 

It is not enough that a modern boiler shop should be equipped with a 
power punch, shears and rolls, which have until recently seemed to constitute 
enough of an equipment to satisfy the ordinary boiler builder that he is doing 
justice to his business, his customers and to himself. While these machines are 
labor-savers of the first order, the proportion of work which they contribute in 
the manufacture of a boiler is small in comparison to the balance. 

To overlook any opportunity to cheapen the production of standard com- 
modities is a positive step towards a business failure, and a number of apparently 
insignificant savings amount to perhaps just enough to keep the business afloat. 

To depend upon the sentiment of the consumer for a higher priced home 
product is folly, for when the home consumer recognizes the fact that the local 
manufacturer does not take advantage of recent appliances for cheapening the 
cost of production, he does them an injustice which they repay by trading else- 
where. 

In return for the patronage of a community a manufacturer, in order to 
establish himself on firm ground, must never permit his patrons to pay out their 
money for the loss of time entailed by the use of antiquated or inadequate tools 
or machines. 



r 



USE. 795 



The pneumatic chipping, caulking and light riveting tools, probably broke 
the ice, as it were, of the old methods, and took boiler making methods out of the 
realm of main strength and awkwardness and placed it alongside of machine 
shop practice. Plate steel may now be machined into boilers as legitimately as 
cast steel may be machined into engines. The pneumatic hammers have been a 
great help to boiler makers. In actual test, an operator with the pneumatic ham- 
mer cut off a 2j^-in. tube in 36 seconds as against 2^ minutes by hand, and 46 
tubes were cut off, turned over and beaded with the same tool, in an hour and 
three-quarters as against five hours doing the same work in the ordinary manner. 

Horizontal boiler seams may be caulked and trimmed in one-third of the 
time required by hand labor, and another great advantage is, that in using the 
pneumatic tool the quality of the blow is the same, consequently the caulking 
should be perfect; whereas, in hand caulking, unless done by a very skilled me- 
chanic, the quality of the blows varies considerably. The caulking is, therefore, 
not homogeneous, the heavier blows tending to reduce the effectiveness of the 
caulking done in a lighter manner. 

For re-caulking an old boiler or re-caulking seams that have been im- 
perfectly done, the pneumatic hammer is a most advantageous tool. A fresh cut 
can be made on the sheet in a very short time and in a perfect manner, and the 
boiler be re-caulked with the tool so as to leave the seam in as good shape as if it 
had been recently manufactured. 

It is only necessary to watch the operation of one of these tools in chip- 
ping cast iron in cutting off heavy angles and beams or plates in awkward places 
and positions, to realize what a labor-saving device it is. There are many places 
where chipping and caulking have to be done where it is almost impossible to 
swing a hammer or to properly guide a chisel or caulking tool. Here is where 
the pneumatic tool shows to its greatest advantage. It weighs but a few pounds 
and does not occupy a space more than 12 ins. long, and any place into which the 
arm can be thrust this tool can be pushed and good work be performed. 

These tools are especially valuable in light riveting. Not only do they 
save a great deal of time in ordinary open riveting, but in riveting up pipe they 
prove themselves money makers on every occasion. It is an expensive proposi- 
tion to lay pipe and rivet up the joints in the ordinary manner. Holes have to be 
provided for passing into the pipe the hot rivets, which have to be pushed up 
through the holes and the men have to hold against the riveting from the out- 
side. During all this operation light rivets are becoming cold and the difficulty 
and annoyance and hard work during the whole task make it expensive and the 
results inferior to riveting under ordinary conditions. With the pneumatic tool 
the rivets can be pushed in from the outside; the workmen on the inside of the 
pipe using the pneumatic tool to rivet it up on the inside. The holding is done on 
the outside. The workman inside is furnished with good air to breathe and 
merely has to handle the light tool. No expensive digging out under the pipe 
has to be undertaken in order to rivet the seams next the ground. In short, 
it is entirely probable that riveting in this, manner can be done for at least one- 
third the cost and in a very much better manner than by hand. 

The riveting up of gasometer rivets, stand pipes and tanks, which are set 
up outside, can be done much better and in a great deal less time by the use of 
these labor-saving devices. 



796 USE. 

These pneumatic hammers are not the only pneumatic tools which are itsed 
in modern boiler shops. There are many other appliances ; for instance, pneu- 
matic drill and tap combined, for drilling and tapping out the numerous holes 
required to be made for the stay bolts of fire boxes. 

There is also the pneumatic drill, for drilling holes using ordinary twist 
drills. These machines are extremely easy to handle and they do good work. 

There are pneumatic machines also for expanding tubes into place. 

Every good boiler shop should also have, in addition to a large pneumatic 
crane, small pneumatic lifts for handling heads and sheets and pieces of boilers 
so they can be rapidly placed in position and without the pulling and hauling 
which would be necessitated by hand labor. A pneumatic crane properly in- 
stalled in a boiler shop is a valuable acquisition and should be made powerful 
enough to pick up an ordinary boiler and move it from place to place as re- 
quired, or for final transportation. The entire surface of the shop in this manner 
would be made to yield working space, while with no means of lifting and trans- 
porting boilers over each other a large portion of the ordinary shop space has 
to be left open for gang way, and the annoyance and inconvenience of pushing 
boilers past each other for exit, and the moving of work and tools which are 
frequently in the way, causes a loss of time and annoyance which amounts to 
considerable. 

In the testing of boilers much time and expense could be saved by having 
a water tank on the shop floor in in any convenient place, at sufficient height to 
readily fill any of the boilers for testing. After testing, the water may be ex- 
pelled from the boiler by compressed air, which will shoot the water back into 
the tank in a very small fraction of the time necessary to empty a boiler under 
ordinary circumstances ; in fact, emptying a boiler after testing is one of the slow 
jobs and generally loses a day in shipment, whereas, with the use of compressed 
air, after a boiler has been tested it can be emptied and shipped inside of an hour. 
The water is also saved, which in many localities is a considerable item. 

Besides the pneumatic tools, a well equipped boiler shop should have a 
gang shell driller, for drilling holes in the shell, as required for Government 
boilers, and if the shop is of any considerable size, a head spinning machine and 
furnace would pay for itself in a short time. The ease and rapidity with which 
ordinary boiler heads can be spun into shape and the certainty of turning out 
a first-class job, and the economy with which it can be done, should make it a 
desirable adjunct for any first-class boiler shop. All reasonable sized scraps 
about the shop can be heated in the same furnace, and with the addition to the 
plant of two or three forms of inexpensive hydraulic presses, these scraps could 
be made into manhole crow feet, manhole plates themselves, compressed steel or 
iron flanges, eyes, angle plates and many other pieces which go to furnish up a 
first-class boiler, .which in cheap work are generally made out of cast iron. All 
this work, which consists of scarcely more than operating a lever connected to a 
machine and putting the heated raw material in place, can be done by boys as 
well as by the most experienced men. 

For a large boiler shop the equipment would be incomplete without proper 
pneumatic or hydraulic riveters for heavy work, and finally when boilers are 
finished they can be painted more effectively and in one-third the usual time by 



USE. 797 

the use of pneumatic spray painting machines which are now in use amongst most 
of the large car shops in America. 

A compressed air plant to do all this work for an ordinary shop would be 
a very small one. A 15-h. p. engine, driving a small compressor, could, with 
sufficient receiver capacity, handle all the business of an ordinary shop, unless the 
boiler testing was done with compressed air, which, by the way, is, to the mind 
of the writer, a better method than cold water, for with the use of soap, water 
and a brush to paint the seams, the smallest leak can be instantly detected by 
the bubbles blown, and the rapidity with which the pressure can be introduced 
and released and the absence of water and leakage, makes the whole operation 
more desirable. 

A valuable addition of any boiler shop would be a portable pneumatic plant 
with the proper tools for doing work away from the shop, such as erecting 
gasometers, stand pipes, putting in riveted water mains and doing any "sheet iron 
work where the use of these tools saves in both expense and time. These plants 
could be small and easily portable and would certainly pay handsomely to the 
shop that possessed them. 

The writer is glad to note that most of our principal shops here in San 
Francisco have, during the last twelve months, been gradually improving their 
equipments and installing many of the tools described above, with the most 
satisfactory results. Never has the output of boilers been so great in San Fran- 
cisco as during the past six or eight months. While our manufacturers here are 
handicapped by a limited field and therefore not enjoying the advantages of man- 
ufacturing considerable numbers at a time, still the differences between the freight 
on raw material and the finished product in this community, acts as a protective 
tariff which partially does away with the disadvantage above mentioned and our 
boiler makers feel that with modern tools and methods, they can hold their own 
in the competition which is everywhere the life of trade.-^E. A. Rix, in The 
Boiler Maker. 



COMPRESSED AIR IN A ROLLING MILL. 

Most of the more successful iron-working establishments now use "air" — 
a little — some a great deal, and among the foremost of the latter class is the 
Passaic Rolling Mill Co. at Paterson, N. J., not only because of their extensive 
use of compressed air, but particularly by reason of the variety of operations per- 
formed by it, several of which are of more than ordinary interest and we believe 
originality. These works cover about 25 acres of ground, employ about 1,200 
men, knd have a monthly output of about 5,000 tons, chiefly structural steel, a 
considerable portion of which is manufactured into bridge trusses, columns, etc.. 
dt the works, so it will be seen that compressed air has there a good field in which 
to demonstrate its value. 

The accompanying illustration shows partially the row of jib cranes; each 
equipped with independent air hoist, used for loading the finished material on 
cars for shipment. The air cylinders for this work are about 6 in. diameter by 
6 ft. stroke, mounted on the mast, the air connection being made with a short 
piece of hose at the top of the crane. 



798 



USE. 



Figure 294 illustrates one of the most interesting applications of compressed 
air; one in which work formerly requiring the services of thirteen men is now 
done by four, and with less danger. By it the capacity of the rolls has been 




FIG. 293. — UNLOADING CARS WITH AIR HOISTS. 



trebled. This apparatus is not operated entirely by compressed air, steam and air 
being assigned to the work for which each was considered best suited. It consists 
of two transfer tables, one on each side of the main rolls of the rolling mill, the 
duty of one of which is to deliver the heated billet to the first roll, move into 



in 



USE. 



799 



position to receive it from the second, move and deliver it to the third, and so on 
till the billet comes out a finished beam. Of course the process described applies 
to the table on one side of the rolls only, the one on the opposite side operating 
in the same way with it. This transfer table consists of a heavy four-wheeled 
carriage A carrying a tilting platform or girder B (with fulcrum at C), the top 
of which consists of rollers operated in either direction by the level gears and 
shaft plainly shown in the cut. The carriage travels in the pit on rails parallel 




FIG. 294 — TRANSFER TABLE. 

I to the rolls in moving from one roll to the next, and the end of the tilting table 
next the rolls is raised and lowered to position for the upper and lower rolls by 
an 18 in. air cylinder located in the yoke D. The crossbend E is connected at its 
center to the piston of this air cylinder and moves the tilting platform by means 
of the side rods fastened to its ends. The action of this cylinder is controlled 
by a special valve F, operated from the engineer's platform at P. The men shown 
in the cut were engaged in changing rolls at the time the photo was taken and are 
in no way connected with the operation of the table, one engineer and a roll tender 



8oo 



USE. 



being all that is required for the apparatus shown in the cut, and the same number 
for the other table (not shown) on the opposite side. 

After the beam leaves the rolls it passes to the hot saw shown in Fig. 295 
where it is trimmed and cut to length. The rollers A, Fig. 295, receive it from the 
rollers on the table, Fig. 294, without any handling or even a pause in its motion, 
so that a few seconds after it has received its last squeeze in the rolls it is being 
cut by the saw. This saw is fed through the beam by the compressed air cylinder 




FIG. 295 — AIR CYLINDER FOR LIFTING HOT S.\W AND DEVICE FOR PLACING BEAMS ON 

EDGE, OPERATED BY AIR. 



B, which is 12 in. diameter by 20 in, stroke; the elastic yet persistent nature of 
the feed given the saw by compressed air is found much better than any other 
method. 

Compressed air performs the next operation on the beam, which is to 
remove it from the rollers (making room for the next) and set it on edge to cool. 
When the beam lays on the rollers after being cut to length the fingers (C) are in 
a horizontal position under it between the rollers, and an air cylinder, 15x36 in., 



USE. 



8oi 



located under the rollers pulls the fingers to a vertical position, bringing the beam 
with it, at the same time carrying it sideways far enough to clear the rollers. 

The rest of the work done by air in these works is being done in many 
places elsewhere, and is consequently of but passing interest. Fig. 296 shows a 
busy corner in the bridge shop — a group of three riveters, two reamers, a chipping 
tool and hoist, all being operated by compressed air. The total pneumatic equip- 
ment of the works, outside of the special apparatus described consists of about 40 




FIG. 296 — AIR HOIST, AIR DRILLS, AIR HAMMER AND AIR RIVETERS. 



cylinder hoists, 12 riveters, 5 drills and reamers, and 2 chipping tools. They 
now have nearly completed a very interesting device for charging the heating 
furnace, which we hope to describe in a future article. This equipment is being 
constantly increased, especially the number of hoists, which vary from 4 in. to 12 
in. diameter and up to 6 or 8 foot lift, used for handling material throughout 
the works. 

Fig. 297 is a ground plan showing the approximate location of these com- 
pressed air appliances. 



8o2 



USE. 



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■^ rIG. 297— PIvAN OF THE PASSAIC ROI.WNG Mil,!,, PATERSON, 
N. J., SHOWING THE DISTRIBUTION OF COMPRESSED 
AIR APPWANCES. 



USE. 803 



r 

H^ Great credit is due their master mechanic, Mr. J. E. Jones, to whose energy 
and inventive ability is largely due the successful installation of this aggregation 
of pneumatic appliances, the value of which it is difficult to even estimate, and the 
cost of which was comparatively very low. The officers of the company (all of 
whom are great advocates of the use of compressed air) are : Mr. Watts Cooke. 
President; Mr. W. O. Fayerweather, Vice-President and Treasurer; Mr. A. C. 
Fairchild, Secretary ; Mr. John K. Cooke, Superintendent, and Mr. G. H. Blakeley, 
Chief Engineer. 

Amxple compressed air for this plant is furnished by one Class A Straight 
Line Piston Inlet Ingersoll-Sergeant Air Compressor, which is controlled by an 
automatic device, so that steam is used only in proportion to air used in the works, 
which naturally varies within wide limits. 

These works seem to be more favorably situated than would at first thought 
appear ; they have in their yards the tracks of the Delaware, Lackawanna & West- 
ern and Erie Railroads and are very convenient to the New York market. 

HARRY M. PERRY. 



COMPRESSED AIR IN SHOPS. 



Compressed Air has from time to time published illustrations and de- 
scriptions of compressed air appliances in railroad shops. We have endeavored 
to exercise care in dissociating patented and theoretical designs from those 
which have been put into practical operation and which have established them- 
selves in a field of usefulness. We illustrate herewith some of the successful 
cessful applications of compressed air in railroad shops, the cuts being made 
from photographs taken by our representative. 

In no class of work has compressed air such a varied usefulness as in 
shops, and it is» much to the credit of the mechanical engineers connected with 
railroad shops that they should have assumed the initiative in this important 
industrial use of air and that they have developed it to so large an extent. We 
understand that Mr. Gordon, Master Mechanic of the P. W. & B. shops at Wil- 
mington, Del., about the year 1882, and Mr. Dolbeer at the Renovo shops of the 
P. R. R. about the same time, were pioneers in the application of compressed 
I air to railroad shops. We will be glad to have the names of persoils who may 
ihave applied air to the shops prior to the date given. The first application was, 
we believe, to a hoist. Those who are familiar with railroad shops know the 
importance of a small, portable and powerful hoist, and we are quite safe in say- 
ing that prior to the introduction of the air hoist there had been nothing which 
met the requirements so well. Next in importance to the hoist is the application 
of air to portable motors, such as drills, reamers, taps, riveters, chipping tools, 
etc. Such uses can hardly be called exclusive, as other powers have been applied 
with, we think, less economy and success. There are, however, certain exclusive 
applications of air, such as cleaning cars, painting and pumping, which have of 
late come into general use, and which invariably argue as a good reason why 
a compressed air plant should be installed in the shop. There are many things 



8o4 USE. 

now done by compressed air which might be done by electricity, but there are 
few things which electricity can do in a shop which cannot be done equally as 
well by air. Air power has a more general application and has a greater field of 
usefulness in a shop. With the single exception of lighting, what is there about 
a shop which can be done by electricity for which compressed air is not just as 
applicable? The great advantage of electricity is in long distance transmission 
of large powers and in the ease with which it is subdivided and distributed. 
These advantages are not apparent in a shop equipment. The power distributed 
is usually small and easily transmitted throughout the limits of the shop with 
practically no loss by friction. Piping a shop is an easier operation than wiring; 
the tools are at hand, and the men, down to the most inexperienced, are capable 
of understanding and managing a pipe line. There is less liability to leakage, 
because when air leaks it whistles, while with electricity much loss might occur 
for months or years without discovery. There is always the element of danger 
by fire and otherwise in an electric installation, while air is so safe that it has 
been called the "humane power." We have no doubt that, when properly under- 
stood, insurance rates might be affected favorably to an air plant. It certainly 
seems desirable in a place where there is so much oil and so many combustible 
elements to use that power which, when generally distributed throughout the 
shop, is perfectly safe. As air and electricity are both secondary powers, it costs 
perhaps as much to produce one as the other; but in any system where the use 
of the power is variable and intermittent, air is more economical. Upon this 
point we can stand with much assurance. If the motor does not consume air, 
the generator is simply reduced in speed or stopped altogether by an automatic 
governor. But we have heard it said that the most important advantage in air 
over electricity is that air machines are easily understood by the men in the shop, 
and if anything happens repairs may be promptly made. Trouble in an electric 
plant calls for a telegram to the electrician, who is not always as available as he 
Is expensive. 



AIR FOR SHIP BUILDING. 



Compressed air for ship building is being used extensively in the large 
ship yards of the country. Following is a record of its use at the Chicago Ship 
Building Company's yard: 

They commenced to use compressed air in this plant about two years ago, 
putting in at that time a couple of pneumatic hammers for caulking and chip- 
ping in the machine shop and outside on ships under construction. This part of 
the plant has been in constant use ever since, and with very great success. Both 
edge caulking and butt caulking are done much more rapidly and cheaply than 
either can be done by hand, and make better work in every respect. About |l 
eighteen months ago they started to experiment with portable pneumatic com- 
pression riveters for use in driving rivets in ships on the stocks. The riveter 
was the ordinary form of bow riveter, and the only trouble had with it was in / 
arranging to handle it quickly in the ship. After considerable experimenting, a 
rig was finally gotten up which enabled them to pass rapidly from one rivet to 



USE. 805 

another, and they have used these riveters with much success ever since on a 
number of vessels. 

Last summer it occurred to the company to experiment with the pneumatic 
hammers for driving rivets, and in connection with a pneumatic holder-on, which 
was devised by themselves, the result in that class of work has been very satis- 
factory. 

The latest application made is in the form of a light wrought iron bow of 
about 4J/2 ft. gap, with a hammer fastened on one side and a pneumatic holder- 
on on the other side. This is suspended by a chain fall from a portable section 
of overhead tramway, and has been very successful in use. The whole arrange- 
ment weighs only about 400 lbs., against a weight of nearly a ton on a com- 
pression riveter of the same gap and capacity. Altogether they are driving now 
from 15 to 20 per cent, of all the rivets in the ships by these riveters. 

Pneumatic reamers for fairing the rivet holes have been adopted, and a 
number of them are in use. Two men with one of these power reamers can do 
the work of six or eight men working by hand, and on some classes of work can 
ream as many as three thousand holes a day. Pneumatic hoists are also used to 
some extent in the shops, and the extension of the application of the air goes 
along at a rapid rate. 

The first compressor put in had a capacity of about 200 cubic feet free air 
per minute, and the one now being used has about 800 cubic feet capacity. Air is 
used at a pressure of from 90 to 100 lbs. Compressed air machines of their own 
designing are used for painting and whitewashing the shops and for painting the 
iron work on ships. They find it works very well on a plain flat surface like 
the outside of the hull, but it has not been very successful on the inside work. 



MONON RAILROAD SHOP. 



When the "Monon" Railroad erected new shops at Lafayette, Indiana, 
about a year ago, they installed. 10" x lo^" x 12" Piston Inlet Class "A" Air 
Compressor, which they considered would be ample to operate any compressed 
air appliance they might put in for some time to come. 

The use of compressed air has grown so rapidly in this shop that an order 
was recently placed for a Duplex Ingersoll-Sergeant Compressor, with both 
steam and air cylinders compounded and of about four times the capacity of the 
original machine installed. 

At present they are using, in connection with the small compressor, air 
appliances as follows, some of which we illustrate and describe in detail, the 
description being kindly furnished to us by Mr. Charles Coller, Master Car 
Builder of the road. 

Fig. 298. Hose Press. — A bench 30" wide, 8' long, set up against shop wall ; 
at each end is an upright post, 9" x 12" x 8', secured to bench and against wall. 
To each post is bolted one cylinder, 5" in diameter, 10" stroke. These are old 
engine steam brake cylinders taken from scrap pile. The one on the right hand 
is used for clamping hose, having cast dies of different sizes for the different 



8o6 



USE. 



sized hose. These dies slip into the cast iron blocks, which are fulcrumed to 
piston rod on cylinder, and the lower one is bolted to top of bench. The cylinder 
on the left has piston rod connected to the long arm of the tongs, or clamp, which 
is pivoted to a fulcrum bolted to bench. This is used for clamping hose bands 
onto hose while bolt is being inserted; is also used for cutting old hose off 
couplings. 

The 8" X 12" freight air cjdinder shown is bolted on top of bench. There 
are a series of dies which fit into the end of the piston shank, which hold all 
patterns of steam and air hose couplings and nipples to proper position to be 
inserted into hose. Above this cylinder is a shelf set up on brackets, upon 
which, standing in an upright position, is an auxiliary reservoir. This is used 
for testing plain triple valves. On the upper side of the bench is bolted a 




FIG. 298 HOSE PRESS. 

freight car auxiliary and cylinder complete. This is used for testing 
quick-action triple valves. At the end of bench, to the left, is one 
air brake and one signal hose, which are attached to pipe leading from main 
reservoir. To these hose, all hose fitted up are coupled and a cap or plug put on 
the opposite end, and full pressure is turned on in order to be positive the hose 
leaves the shop in good condition with regard to leakage. 

Fig. 299. Car Lifting Jack. — Used for lifting coaches. This jack has a 
piston 15" diameter, with 26" stroke ; piston rod is constructed of a piece of pipe 
6" in diameter, 30" long. There is a sleeve 5" long on piston, which extends into 
lower end of pipe and is bolted to same. There is a cap with four lugs, V/i" 
long, cast on under side, which drops on inside of upper end of pipe. The cast- 
ings are all malleable iron. 

The jack is bolted to a small truck of the warehouse type, being easily 
moved around shop or yard. Both jacks are operated by one man, the hose run- 



USE. 



807 



jing in "Y" shape from jacks to main hose, which has a cock attached to it. 

Khere is a %" air cock attached to each jack, used for releasing air. 

H Fig. 300. Car Wheel Hoist. — Used for loading and unloading loose 

Hir wheels not on axles. There is a pit 3' wide, 5' long and 6' deep in the 
ground, walled up with brick, and bottom of same laid with grout 6" deep. On 
top of this are three pieces of scrap "T" rail bolted to a piece of boiler plate, and 
to this plate are bolted two cylinders of 7" pipe, 5' long. The plunger, or piston 
rod, is made of 6" pipe and fastened to piston at lower end, and a cast iron plate, 
is" diameter with sleeve 5" long, inserted into the upper end. To these plates 
are bolted a platform of oak timber, 3' wide by 5' long, the cross pieces being 

, sandwiched with iron plates. There are two posts, 6" x 6" x 20" long, framed 
to platform for wheels to rest against. There are four posts set suitable 




FIG. 299 (AK LIFTING JACK. 



distances between car to be loaded, or unloaded, and the air hoist. These are 
let into the ground about 3', and boarded up on each side. The two forward 
posts nearest car have a piece of oak, 5" x 5", with ends rounded and pivoted to 
fit into slots in the posts; on this cross piece rests the stage plank. The end of 
stage next to hoist is hinged to platform of same. When air is applied this 
throws stage plank about 6" inside of car door, and when released it inclines 
same in a position that will clear car about one foot. 

The hoist is operated, and all wheels loaded and unloaded by one man, he 
taking all numbers and defects, etc., of wheels. Time consumed to load one car 
of 80 to 100 wheels being 50 to 60 minutes; same being done piece-work. 

Fig. 301. Car Wheel and Axle Hoist. — Overhead traveling hoist used for 
iding and unloading wheels on axles. This is constructed of two tripods, the 
js of same being 3" gas pipe fitted to cast iron shoes at the bottom. The shoes 



8o8 



USE. 




FIG. 300 — CAR WHEEL HOIST. 




FIG. 301 — CAR WHEEL AND AXLE HOIST. 



r 



USE. 



809 



rest on blocks of stone, 20" square, let into the ground and set in grout. Bolts 
which hold the shoes are let into stone and leaded. The top castings are made 
to take the three legs and the ends of the two *1" beams of 5" height and 30". 
long; these being trussed on under side with i" rods. The trolley is constructed 
of four wheels, 12" diameter, with flanges on outside, and have axles of V/z" 
diameter. To this is suspended a hanger, made "V" shape, which is made of Ij4" 
X 4J^" iron. Suspended to this, by a clevis, is a cylinder 10" diameter, 5' stroke. 
Alongside of car track, and running in opposite direction, is a series of tracks 
on which wheels are stored. Running parallel with car track, and about 20' 
from same, is a track of 20" gauge. This divides the series of tracks men- 
tioned above; on one side are stored the wheels for shipment, and on the other 
side the old wheels unloaded. This track runs through the shop, alongside axle 




FIG. 302 — CARPET NOZZLE. 

lathes and wheel press. On this track is a truck, the top of which is on a level 
v/ith top of rails on cross track and top of platform of wheel press, making it 
easy work for one man to roll a pair of wheels on same from press platform, or 
any one of the cross tracks, running same out and rolling wheels off on track 
directly under hoist. 

Usually two men operate this hoist loading and unloading — one man on the 
car, and the other on the car handling wheels. A car consisting of 14 to 18 pairs 
of wheels is loaded, or unloaded, in 20 to 30 minutes; same being done piece- 
work. 

Fig. 302. Carpet Nozzle. — Showing an air nozzle used for cleaning car- 
pets, cushions, etc., and interior of coaches; this appliance being in use in most 
railroad shops employing compressed air. 

Fig. 303. Pneumatic Scrap Shears.— This is an old-time tool, being made 
of boiler plates by one of the veteran boiler makers in charge of this company's 



I 



8io 



USE. 



boiler shop, some forty years ago. It was consigned to a resting place in the 
scrap yard, but when the "air" fever struck us we considered it economy to set 
this tool up again, attach a 14" car cylinder to it and operate same in our scrap 
shed, for cutting off old bolts, instead of trucking same into shop and then 
trucking the scrap cuttings out again to the pile. With one man and a pressure 
of 60 pounds, of air, this veteran tool is cutting off all old bolts i]4", and under, 
in scrap shed, the only handling being to take them to the screw machine to be 
threaded, and our supply is kept up in good shape in the bolt room and a small 
siock carried in scrap pile. 

Fig. 304. Pneumatic Punch. — This tool is a brother to the shears, as 
described and shown in photograph Fig. 7. It is made in the same manner, and 
about the same time, and, like the old shears, we took pity upon this tool in its 
old age and applied the elixir of life through a second-hand 10 x 12" car cylinder 




FIG. 303 — PNEUMATIC SCRAP SHEARS. 



and set it up in the shop, and at first trial punched a Ys" hole through >4" iron 
with 50 pounds air pressure. We punch at the rate of six holes per minute in 
34" to ^" iron with punches of same diameter. 

Fig. 305. Air Compressor. — This shows the small Piston Inlet Air Com- 
pressor now being used to operate the pneumatic tools. This machine will 
shortly be replaced by the Cross Compound Compressor of the following di- 
mensions : 

High pressure steam cylinder, 14" in diam. 
Low " " " 26" 

Low pressure air cylinder, 22^4" 

High " " " 14K" 

Stroke, 18". 
This machine will be proportioned for a steam and air pressure of 125 
pounds. 



USE. 



8ii 



Overhead Trolley Timber Hoist. — (not illustrated.) — This is used in 
wood machine shop. There is a track leading from lumber yard through the 
shop ; on one side of track is a heavy four-side timber dresser ; on the other side 



• r * 


1 ■ 










^ 


' ■» 4 


'%'.- 





FIG, 304 — PNEUMATIC PUNCH. 




FIG. 305 — AIR COMPRESSOR. 

and adjoining track is a 40" cut-off saw; 12' back of this is a Fay Planer. Above 
J these, running in opposite direction, is suspended a trolley track, 40' long. Sus- 
pended from this is an air hoist, cylinder 5" diameter with 4' stroke. Attached 



8i2 USE. . . 

to this is a half-inch hose running from distributing air pipe. There is a re- 
ducing valve between pipe and hose. On lower end of piston rod there is slipped 
a spiral spring to relieve any shock to trolley when the air is applied too sud- 
denly. This, however, never occurs when the reducing valve is in good order. 

A truck is loaded with heavy timber in the yard and run into the shop. 
The timber is then picked up by the hoist and conveyed to cut-off saw, and from 
saw to either side of track to planers. 

There were formerly two men employed at this saw, cutting off and truck- 
ing timber; the work is now done by one man. There is a rope, with each end 
attached to hoist and passing over sheave at end of trolley. The operator stands 
at the saw and moves the timber to either side of the shop with little exertion. 
The timber suspended from hoist is of the following dimensions: 7^" x I2j^" 
X 19". 

Lifting Jack — (not illustrated.) — Used at wheel turning lathe. This is 
constructed of two cast-off 5" x 10" steam cylinders bolted to a block 9" x 
12". There is a piece of boiler steel formed to fit the shape of the axle and ful- 
crumed to each piston rod, which is set in middle of lathe. Wheels are run into 
shop on track mentioned before as being used for transferring wheels; there are 
two pieces of timber laid across lathe pit and against truck. 

Other air tools at present in operation in these shops are as follows : 

MACHINE SHOP. 

Three (3) Rotary Drilling and Tapping Machines. 

BOILER SHOP. 

One (i) Punch for sheet iron. 

One (i) Punch for boiler plate. ' 1 

One (i) 14" Hoist. 

Two (2) Caulking Tools, 

One (i) Stay Bolt Breaker. 

One (i) Stay Bolt Cutter. 

BLACKSMITH SHOP. 

One (i) Small Bulldozer. 

Two (2) Babbitt Melting Furnaces. : ■ 

CAR DEPARTMENT. 

One (i) 10 X 12 Press for pressing oil out of waste. 

Air is also used for cleaning lubricators, testing air brake pumps and 
testing air brakes. 



COMPRESSED AIR IN A SAWMILL. 

In the early part of 1898 a compressed air plant was installed in the saw-?- 
mill of Wm. Engel & Co., Orono, Me., and all the appliances hitherto actuated byrj 
steam were made to run by compressed air. The chief object of adopting com- 
pressed air to operate sawmill appliances was to minimize the fire risk. Instead| 
of dangerous belts, pipes now conduct the power and the details of the plant will 



USE. 



813 



irove interesting. An Ingersoll-Sergeant Class "B" Air Compressor is operated 
iy a large water wheel. Air is compressed and stored in a receiver and dis- 




FIG. 306 — STEAM FEED CUTTING-OFF SAW. 

^ributed through pipes to any part of the mill desired. The power generating 
plant, consequently, is so simple that any person of ordinary intelligence can 




FIG. 307 — THE NEW "aLLIS" BXND MILL. 

easily superintend its operation. The machinery in use at the Wm. Engel mill is 
the same as that used in steam sawmills. Air at 90 to 100 lbs. pressure is carried 



8i4 USE. 

in the receiver and pipe line to the different machines that air is used in. The 
following devices are necessary to operate modern sawmills, and combined with 
the use of compressed air the method of producing lumber may be fairly realized. 

ALLIS JUMP SAW RIG. 

Air is used to raise and lower an Allis Jump Saw Rig that is placed in the 
log slide to cut off the logs at the right length. 

ALLIS LOG FLIPPER. 

This machine throws the log out of the log slide on the log deck, where they 
are stopped by a 

KLINE LOG ROLLER. 

This appliance holds them in place until the sawyer wants the log on the 
carriage, when he does the same as he would in any steam mill, that is, step on 




J 



FIG. 308 — DIRECT ACTING STEAM LOG FLIPPER FOR ROLLING LOGS OUT OF THE LOG SLIDE. 
OPERATED BY COMPRESSED AIR. 

the treadle in the floor; the air does the rest. At the same time he has one hand 
on the 

HILL STEAM NIGGER LEVER 

and the other hand on the carriage lever; when the air gets in its work again 
with the nigger he places the log just right to saw and with 

beck's TWIN ENGINE FEED . 

that runs the carriage back and forth to the 

BAND saw, 

which puts the logs into lumber, which goes on down the mill on live rollers to 
some Allis Jump Saws that set in the roller casing to trim the lumber and timber 



USE. 



815 



rork, also to cut up edgings and slabs. Besides the machines which have been 
)oken of which use the air successfully are a 

STEAM PUMP 

fire protection, it is also used to blow a 

LARGE WHISTLE 

Start and stop the mill at meal times. 

This mill is operated 11 hours per day and pro'duced from 50,000 to 65,000 
;t of lumber daily, and goes to show that compressed air does the work as well 




FIG. 309 — HILL S PATENT DOUBLE CYLINDER STEAM 

PRESSED AIR. 



NIGGER. OPERATED BY CX)Mi 



as steam, with the advantages of lowering the rate of insurance, which is ex- 
tremely high on sawmill plants, and the avoidance of disagreeable conditions that 
the use of steam entails. 



APPLICATIONS OF COMPRESSED AIR IN RAILROAD SHOP 

PRACTICE.* 

Wherever steam has gone to create the necessity and opportunity for it, 
there compressed air has followed, going often where steam could not go, rivalled 
only in its adaptability and convenience by electricity. In all branches of industry 

♦ From an address before the St. Louis Railway Club. 



8i6 USE. 

and manufacture it has its hundreds of applications, and this is no mere figure 
of speech, for there lies before me a list of nearly four hundred different uses 
of compressed air, and this list is doubtless incomplete. 

In case of transmission and of application, in adaptability, as well as in 
cost of installation and maintenance, air and electricity are on almost equal foot- 
ing, and it is only when we consider the tools by which this power is applied that 
we find the advantages of the former over the latter. It is in the greater sim- 
plicity of the motors required for its local application that air may base its claim 
to distinction. In addition to the important difference in cost, due to the greater 
simplicity of construction, the air-driven tool possesses the advantage, so requisite 
for its proper use, of being readily understood by the operator — a claim which 
cannot be made for electricity for some time to come, for the confusion and 
dread, in the ordinary mechanic's mind, of all things electrical, are not soon dis- 
pelled. 

The figures relating to saving in time and labor as given in this paper 
were, without exception, obtained from the master mechanics or general fore- 
men, and in almost every case these estimates were verified by consultation with 
the shop foreman and the operators themselves. Care has been taken to insure 
that such figures represent ordinary conditions, and records made particularly 
for the purpose of showing a saving, or under unusually favorable circumstances, 
have been excluded or modified, so that the figures given may with reason be 
relied upon for the conditions mentioned and under which they were obtained. 
In one of the railroad shops, and one from which more than its share of this in- 
formation has been drawn, the change from handwork to the use of air tools 
has been made within the last eighteen months, and many of the figures are de- 
rived from daily records, and all the information is fresh in the minds of those 
concerned. In all other cases where the figures given were not based on written ^ 
records, the results, as intimated above, have been carefully scrutinized. f 

For riveting, the use of the pneumatic holder-on adds much to the tight- 
ness of the work. In one of the shops visited, in riveting the mud ring on a con- 
solidation locomotive by the air hammer, the saving over riveting by hand was 
67 per cent., and this class of work is typical of much that is done by the ham- 
mer. 

One of the most interesting operations performed by the pneumatic ham- 
mer is the chipping of wrought iron and steel. In one instance, in work of this 
character, done on a "ten-wheeler," the work formerly requiring the labor of a 
boiler-maker and helper for two days is now done in one-quarter of that time. 

In a particular piece of work on saddles, typical of many situations in 
which the pneumatic drill is used, a machinist and helper accomplisTied in three 
hours what would have required by means of the ratchet drill sixteen hours, and j 
this saving of 70 per cent, is by no means extraordinary. ... In one of our i' 
Chicago boiler shops the time required for work done by the pneumatic breast ' 
drill was to the time consumed on the same work when done by the hand-driven 
tool, in the ratio of one to ten or one to twelve. The various other uses to which 
the motors of all these air drills may be put present themselves at once, and by 
one of these applications— the grinding and facing of steam pipes— there is now 



] 



USE. •■ ■■ - gj^ 

:bmplished in fifteen minutes what formerI>, by tedious hand work, took an 
mr or more. 

The facility with which compressed air may be made to meet particular 
;ds has created in many shops, in addition to the regular pneumatic tools, a 
iber of special devises, one of which is a press for the brasses of driving 
ces. This machine drives the brasses for all the boxes that go through the 
msiest shop on one of the largest railroads in the West. With it two men and 
a helper now do all the work formerly done by eight men, and it has become as 
indispensable to its owners as the lathe beside which it works. 

For chipping out defective stays on an ordinary American type locomotive, 
which had come into the shop with about the usual number to be replaced, three 
hours' work by an apprentice boy sufficed to do the cutting-out which it would 
otherwise have taken a boilermaker an entire day to do. In this case the boy 
can undertake, without risk of damaging the plate, work which would not ordin- 
arily have been intrusted to him with the hammer and chisel. . . . The ham- 
mer used for flue beading effects about the same saving as it does in other classes 
of work. To bead 150 flues by hand cost $2.35, while the same work done with 
the aid of air amounted to 60 cents. 

The portable riveting machine with fixed yokes can, of course, do better 
work than the hand hammer, and for a great variety of work will produce as 
good results as the stationary pneumatic riveter, besides being much more con- 
venient. "With these riveters," to quote the foreman of one of the boiler shops, 
referred to above, "we can do with three men (two boilermakers and one helper) 
twice the amount of work formerly done by three boilermakers and one helper 
riveting by hand." These machines will operate successfully on plates up to about 
7/s in. in thickness, and for work of this class will compete in their results with hy- 
draulic riveting. Indeed, the foreman in the same shop informed me with con- 
siderable satisfaction that work done by one of these riveters had been inspected 
and passed as hydraulic-riveted, a few days previous, by an inspector of one of 
our best known boiler-inspection companies, who was with difficiilty convinced of 
his mistake. 

One type of air-operated nippers cut off in one case all the stays in the 
firebox of a Brooks "ten-wheeler" in three hours where handled by two boys, a 
job which formerly occupied a boilermaker and helper nearly two days. This 
i.<; a saving in cost of about 90 per cent., and the same work with this tool in 
another erjecting shop results in a saving of 86 per cent. The nippers cutting off 
from both sides at once do not injure the sheet or loosen the thread, as may be 
done by chipping them off. 

Passing now to the car shops, we may note the drill again at work, this 
time on wood — a drill, of course, adapted to this purpose, running at a higher 
rate of speed than the metal drill and weighing usually not more than twelve or 
fifteen pounds. One of these tools has a record of boring through 5 inches of 
oak a 2>^-inch hole in less than twenty seconds— a statement which is particu- 
larly significant to any one who has ever tried to bore a 2j/^-inch hole in oak. 
This drill, in the car shop in rip-rap work, produces a saving of time even greater 
than that effected by the drill in machine shop operations. 



8i8 USE. 

The saving to be effected by the paint sprayer varies, of course, with the 
character of the work. In general, the larger the area to be covered the greater 
the economy in the use of the sprayer, although the intricacy of the work modi- 
fies this. The saving in painting trucks is about 85 per cent., while in the case of 
box car painting the records kept for several days show a decrease in cost of 90 
per cent. . . . The paint burner is a compressed air and oil jet, and -by its 
use four men have been found to do in ten hours what would by other methods 
usually require two days and a half. ... In one shop inspected two boys 
were doing in ten hours with a sand blast what formerly occupied two men five 
or six days, and this saving of 80 per cent, does not represent the total economy ; 
for by the sand blast the paint and rust are so thoroughly removed from even the 
smallest pit that the new paint lasts much longer and the tank is in the paint 
shop less frequently than when merely scraped. This same machine is used for 
sanding the roofs and ends of cars. 

The car journal turner illustrates very forcibly one of the fundamental 
reasons for the general success of pneumatic tools — namely, the ability of local 
application and the avoidance of outlay of time and labor in transporting the 
work to the tool. We have here a machine-shop operation transferred out of 
doors, and a car journal being turned in nearly its original position. This tool 
takes two cuts and a finishing cut on a car axle in about an hour. The ordinary 
drill is its motor, which is detachable, and consequently available for other work. 

The pneumatic fire kindler is an important piece of apparatus in the round- 
house. It is simply a compressed-air oil burner of the simplest construction, but 
of a usefulness entirely out of proportion to its simplicity. It is used above the 
coal and without any kindling material. Some of the results of tests conducted 
by the mechanical engineering department of the University of Illinois with this 
instrument may be of interest. The tests were made to determine the relative 
costs of kindling fires by wood and by crude petroleum, the latter being burned 
by means of a fire kindler. The boiler pressure raised in each case was the same ; 
the time required to reach this pressure was one hour and ten minutes kindling 
by oil and one hour and forty-four minutes kindling by wood. The total cost, 
which in each case includes cost of labor, coal and the kindling material, amounts 
to 34 cents for oil and 61 cents for wood, on a basis of oil at 2^ cents per gallon 
and coal 75 cents per ton — a gain in favor of the oil of about 45 per cent. 

In the tables below are the averages of all the figures given in the fore- 
going. The conditions they represent are normal and such as exist in all shops. 
All extraordinary records or test cases have been excluded, and the results given 
may safely be applied in making deductions for conditions similar to those noted 
in the table. 

I have confined my attention to the saving effected by the tools themselves, 
without regard to the outlay at the compressor, but the question naturally sug- 
gests itself: What does it cost to compress the air? This is a question easily 
enough answered in specific cases, but which must necessarily be differently an- 
swered in every case. In one shop, from which many of these figures were drawn, 
the decrease in the saving effected by the tools themselves, due to consideration 
of the cost of compression, amounts to about 15 per cent, at the most, which still 
leayes a net saving of from 50 to 60 per cent. These figures must be taken as 



r 



USE. 



819 



representing only this one case, and further generalization would be fruitless. 
That the cost of compression, combined with the interest on the cost of installa- 
tions and maintenance, would be prohibitive of the use of pneumatic tools in some 
cases, is entirely conceivable; but that this should be true in a railroad shop of 
any considerable size is hardly credible. 

Among the various men who have supplied the foregoing. information, the 
most enthusiastic advocate of compressed air was the general foreman of a plant 
where 1,800 cubic feet of air are used per minute, and where almost every one of 

TABLE TZ- 



Tool and General Character of Work. 



Pneumatic hammer, general foundry work— chipping . . 
" riveting on mud ring and on firebox 

" chipping flue sheet 

" beading flues 

" general boiler-shop work 

" cutting out broken firebox stays 

" cutting off staybolt heads 

Riveter, boiler riveting 

Drill, drilling saddles. 

" in general machine-shop work 

" drilling for stays 

" in general boiler-shop work 

" facing steam pipes 

" tapping for stays 

" reaming crown sheet 

Breast drill, general work 

Staybolt nippers, cutting off stays 

Driving-box press, pressing brasses 

Paint sprayer, painting box cars 

"' ' ' car trucks 

Paint burner, cleaning off passenger cars 

Sand blast, cleaning tanks 

Air jet, cleaning cushions 



Saving. 



Per cent. 


Per cent. 


of Cost. 


of Time. 


67 to 75 


67 to 75 


67 





84 


75 


75 


75 


60 




70 


70 


68 




66 


50 


70 


70 


75 


75 


50 


50 


75 


75 


75 


75 


65 




70 





90 


90 


73 to 90 ♦ 


75 to 90 


68 





67 


67 


87 


87 


67 


67 


90 


83 


50 


50 



the devices mentioned in this paper are in daily operation. It can no longer be 
said that the use of compressed air is in its infancy, nor can the old charges of 
unreliability and uncertainty in its action and of great wastefulness in its trans- 
mission be substantiated. The use of compressed air in shops is no longer a sub- 
ject of controversy. The field is already fairly well occupied and the possibilities 
are pretty clearly understood. edward c. schmidt. 



PNEUMATIC CYANIDE PROCESS. 

Under various forms the mining papers of the West have been printing the 
account of what is called the Pneumatic Cyanide Process. It is claimed that it 
will revolutionize the treatment of or^. 

The features of the "Pneumatic" process are so easily understood that it 
does not require an "expert" or a thorough chemist to appreciate them', for every 
mining man has had more or less experience with compressed air, and most of 
them know something about the cyanide process and understand that oxygen is 
absolutely necessary in a solution of cyanide of potassium in order to form a 



820 



USE. 



new compound called "Cyanogen," which is the true solvent of the gold. They 
know also that agitation hastens the process of dissolving and extracting the 
values during the leaching process, because agitation, or stirring, enables the 
oxygen of the air to reach the solution more rapidly to form "Cyanogen" and also 
to bring the ore and solution into more intimate contact, and does in a few hours 
what it takes days to do if the ore and solution remain unmoved in the leaching 
vats. 

Many attempts have been made to stir or agitate the mass of leaching ore 
by machinery; but the great cost of power, expensive construction, breakage of 




FIG. 310 SHOWS A SERIES OF LEACHING VATS, OR TANKS, FITTED WITH PIPES AND 

VALVES FOR THE INTRODUCTION AND CONTROL OF THE COMPRESSED AIR. | 

parts, etc., have caused them to be abandoned, and mill owners have gone back to 
the old slow process of letting the ore stand for days in the leaching vats because 
there was no practical and cheap way of agitating them, or of getting the oxygen 
through the solution, except by the slow absorption from the atmosphere. 

Just at this time, when it seemed as if improvement in the cyanide process 
was at a standstill, the "Pneumatic" process comes forward with a method so 
simple and so effective that, as we said before, it is a wonder that it was not 
thought of sooner. 

It is simply the introduction of strong currents of compressed air into the 
bottom of the leaching vats, which force their way upward bubbling and boiling 




FIG. 311 IS A CROSS SECTION, CUT THROUGH THE MIDDLE OF FIG. 3IO, AND SHOWS THE 

AIR PIPES BETWEEN THE TRUE AND THE PERFORATED FALSE BOTTOMS OF THE VATS, 

AND THE TRAP DOOR IN THE BOTTOM FOR DISCHARGING THE LEACHBD REFUSE. 



through the mass of crushed ores and cyanide solution, and thus furnish both the 
oxygen and the agitation needed for the rapid and thorough extraction of the 
gold. This method of forcing the air through the leaching ores can be readily 
understood by means of the cuts shown. 

Fig. 312 is a view of the bottom of a leaching vat, with a portion of the per- 
forated false bottom cut away to show the coil of perforated air pipe, by which 
the compressed air is evenly distributed over the entire bottom of the vat. 

It can be readily seen from these illustrations how fully this process solves 
the problem of leaching the ores rapidly and thoroughly — requiring only hours 



USE. 821 



i where old methods required days. It also drives all the slimes to the surface, 
where they cannot interfere with percolation, as they do when permitted to settle 
at the bottom of the vats. 
Experience has proven that a hot solution of cyanide of potassium is more 
effective in dissolving gold than a cold one; but until this process was invented, 
no practical method of heating rows of large vats filled with solution and leaching 
ores was known. Now, however, by simply passing the compressed air through 
a small furnace before forcing it into the bottom of the vats, the solution is heated, 
the extraction hastened and increased, and all danger of freezing in cold weather 
obviated; an improvement which mill owners in high altitudes will certainly 
appreciate. 

The method of precipitating the gold from the cyanide solution after the 
leaching process is completed is also an improvement over the present methods, 
and is covered aiid protected by a separate patent. It has all the good qualities of 




FIG. 312. 

the old zinc box, with the addition of three new features which aid in rapid pre- 
cipitation and leave the solution in better condition for using a second time. 

The inventor of the process has been working quietly for nearly three years 
in perfecting it and securing his foreign patents, and it has been before the public 
for only a few weeks. The system is now being installed by the Pneumatic Cya- 
nide Process Co., of Denver, Colo. 



WORKING ROCK DRILLS BY ELECTRICALLY COMPRESSED AIR. 

In some of the German collieries the drills are worked by compressed air, 
but the compression takes place within the mine, not far from the face, the air- 
compressor being driven by an electric motor, taking its current from the regular 
power service of the collieries. German mining engineers are stated to prefer 
this plan to either working the drills by compressed air, the air being compressed 
on the surface, as in England, or to driving the drills by electric motors, and it is 
stated to be more economical, though no figures are given. In Belgium rock- 
drilling by electricity has not been attempted. 



822 USE. 

ROCK CUTTING APPARATUS FOR MINING AND QUARRYING. 

Under this heading come all forms of drills and rock boring apparatus, 
stone saws and other cutters, and it must be admitted that in this class of ma- 
chinery American apparatus is superior to the foreign devices shown. 

In the first place, with the exception of the various types of rock drills, 
foreign manufacturers exhibit absolutely no apparatus for quarrying. 

Secondly, their rock drills range all the way from those operated by com- 
pressed air, through electricity and flexible shafts to hydraulic contrivances, with 
a preference for auger drills, electrically driven. On the other hand, with the 
exception of coal augers, American manufacturers adhere to compressed air and 
steam-driven drills of the reciprocating percussion type, except in the case of 
diamond drills for taking out rock cores for prospecting and other similar pur- 
poses, and extensive and expensive experience has shown the percussion drills 
to best meet the conditions of mining hard, medium or even soft rock; and, as 
a result, there are in operation in the United States over 35,000 rock drills 
operated by steam or compressed air. The American drills are extremely com- 
pact, substantial in construction and very simple in design. 

Continental practice is not standardized, and the few manufacturers of 
drilling apparatus have such a small output that each machine is special, there 
being no attempt at interchangeability of parts. 

The best-known American drills, on the other hand, are made in large 
quantities, and all parts are made with jigs, templates and dies, so that their 
dimensions are identical. This permits cheap and rapid repairs when parts wear 
or break. 

Again, there are absolutely no delicate working parts, no insulation to be 
damaged by oil or water, no switches nor contacts to corrode or burn out, abso- 
lutely no danger from sparks igniting gas or explosives, and no danger to men. 
American manufacturers have two forms of mountings — the tripod, and 
what is known as the shaft-bar, or a straight bar on which the drill is mounted. 
One is used for surface and cut work, the other for shafts and tunnels. Con- 
tinental makers nearly always insist on a cumbersome carriage with a swinging 
arm, on the end of which are clamped one or more drills. Sometimes matters 
are complicated, and a tank, levers, wheels and other devices are added until the 
machine presents a formidable appearance. 

The electric drills are generally of the auger type with twisted or gimlet 
bits rotated by a geared or belted motor and fed forward by a hand-screw. 
Usually water is forced down through a hole in the centre of the drill bit and 
flushes out the hole as the bit advances. These electrical augers may work here, 
but they never would under the conditions imposed in the United States, for the 
electrical parts are exposed, and moisture, grit, etc., would soon put an end to 
their usefulness. 

The reciprocating electric drill finds some admirers, and this is shown by 
there being many manufactured. Extensive experiments with it in the United 
States have shown its absolute inferiority in efficiency, durability and simplicity, 
and its continued use, in face of troubles which it develops, can only be credited 
to a fad and the backing of an enterprising electrical company deserving to sell 
electrical machinery. 



USE. 823 

One form of electrical drill makes a very creditable . showing in its exhi- 
bition colors, but we would prefer a history of three months' operation before 
saying much about it. It consists of a motor encased in a water-tight box, with 
[a flexible shaft attached to a percussion drill mounted on either tripod or shaft 
^bar. Gearing, a small crank and various springs inside produce the reciprocation 
and the blow. 

Another strong reason for the use of compressed air drills is that the trans- 
[mission of the air to the drills in pipes is economical. The pipes are easy to 
install and certain. Further, the introduction of the compressed air into the 
headings causes a decided current of air, which keeps the workings cool and 
fresh and incidentally blows out smoke and gases resulting from blasts. 

Hydraulic drills mounted on enormously heavy carriages and complicated 
looking enough to worry a Yankee machinist, it must be admitted, have done 
good service in special cases, but it can hardly be seriously suggested that they 
are suited for more than a very few cases, and, indeed, even their friends could 
not recommend them for quarrying, general mining or rock excavation. 

One concern, from the United States, exhibits two special quarrying ma- 
chines which attract a good deal of attention. The purpose of both of these ma- 
chines is the same, one of them only being considerably larger. The smaller 
machine consists of two round bars held parallel in a suitable frame, but mounted 
on four adjustable legs, so that the frame can be swung through all angles, from 
vertical to horizontal. On these bars is mounted a carriage, which can be 
moved back and forth along the bars by a small motor. This carriage forms the 
support for a powerful reciprocating drill, which may be operated either by 
steam or compressed air. The drill is equipped with a special cutter, and as il 
rapidly reciprocates and cuts the rock, it is moved back and forth, thus cutting 
a narrow slot the length of the machine and to a depth up to 7^ feet. 

The other machine consists of a heavy four-wheeled truck supporting a 
vertical boiler and a powerful special drill, consisting of a cylinder, a heavy 
piston and rod, and a suitable guide for the cross-head of the piston, which, at 
the same time, constitutes the clamp for the cutting tools. The machine is also 
provided with a feeding mechanism which moves it back and forth along the 
track on which it runs. In this way, a vertical cut 12 feet deep and of indefinite 
length can be made. 

If the types of apparatus signify anything, it may be stated quite con- 
clusively that American methods and apparatus for general quarrying and min- 
ing purposes are in advance of continental practice. No doubt this can be 
attributed to cheapness of labor, conservatism, and, perhaps, a certain amount of 
self-satisfied feeling among continental mining concerns.— J. J. S., in London 
Engineering Times. 



TUNNELING BY COMPRESSED AIR. 

Compressed air is to be employed as the power to dig New York's great 
rapid transit tunnel. Within two weeks a compressor plant costing $60,000 will 
be in full blast at the north end of Union Square. This particular plant will 
operate the bolsters, drills, etc., used by Holbrook, Cabot & Daly, of Boston, who 



824 tJSE. 

have the contract for section 3 of the tunnel, which begins at the middle of 
Great Jones street, in Lafayette Place, and runs along Lafayette Place to Astor 
Place, thence to Fourth avenue, to Park avenue, to Thirty-fourth street. 

Workmen are engaged in laying five-inch steel pipe six inches below the 
surface and along the curb on the west side of Fourth avenue. This pipe line 
will be connected with the compressed air plant, and can be tapped for power at 
any point as readily as gas or water mains could be tapped. 

Henry B. Seaman, engineer for Holbrook, Cabot & Daly, talked of the 
work, which may now be said to be really under way. 

"At first," he said, "we considered the advisability of using electrical ma- 
chines for power, but they proved impracticable. They are largely experimental 
as yet. What we sought was something that would prove applicable over the 
whole of the work, at the same time being as economical and as little of a 
nuisance as possible. 

"The question arose as to whether steam or compressed air would be 
employed and the latter was selected. With steam it would be necessary to have 
separate boilers for each bolster and a set of drills, and this would necessitate 
having two or three boilers on each block. Soft coal would have to be used, too. 

"So we decided to put in a $60,000 compressor plant in an enclosure at the 
north end of the park. Pipes from the plant will have three or four inlets to 
each block, and we can have power at any point. Escaping air will not be ob- 
jectionable like steam, and there will be no offensive odors. There will be no 
danger of frightening horses, 

"There will be five boilers in the plant. The first of these will arrive next 
Tuesday. The pressure will be from eighty to one hundred pounds to the square 
inch." 

No especial machinery to be used on the work has yet been made, Mr. 
Seaman said, with the exception of a derrick designed to impede traffic as little 
as possible. As the work progresses, however, special devices will probably have 
to be employed, as in all such big undertakings. 

"Just what devices we will have to use," said Mr. Seaman, "it is impossible 
to say at the present time. We will have to wait and see the condition of affairs 
under ground. We expect to strike considerable rock between Fourteenth and 
Twenty-second streets." 

Excavations will be made for a short distance at a time, and photographs 
will be taken before the street has been torn up and after the section is com- 
plete, as the contractors desire to show that they will leave the pavement in as 
good condition as it was before they touched it. 



THE USE OF COMPRESSED AIR IN MINES. 

Of late years compressed air has gained greatly in prominence as a means 
for the transmission of power, and now occupies a broad field of usefulness. In 
addition to its value and convenience as a power transmitter for engineering pur- 
poses it possesses also characteristics which make it applicable to a great variety 



USE. 825 

of uses in the manufacturing industries and mechanic arts, in which the element 
of actual transmission of power does not at all enter. A discussion of these, 
however, would not be appropriate here. 

In connection with mining, tunneling, shaft sinking, and kindred operations, 
compressed air has found several of its most important applications. Here, for 
some purposes, it has made a place for itself in competition with steam, but it is 
in conjunction with steam, and other prime movers that compressed air, acting 
purely as an agency for transmitting power, has frequently become indispensable 
for underground work. As compared with steam the employment of compressed 
air for such purposes is particularly valuable and convenient for four reasons : 
First, its transmission loss is small ; second, the troublesome question of the dis- 
[posal of exhaust steam underground is avoided; third, the exhaust air is of direct 
assistance in the ventilation of the confined working places, and fourth, its 
capacity for storing power makes it well adapted for intermittent work. These 
points will be briefly considered. 

The conveyance of steam long distances underground involves serious and 
unavoidable loss from radiation and consequent condensation. The loss due to 
friction is common to both steam and compressed air, and although not equal at 
the same pressure, on account of the greater density of compressed air, the one 
may be taken as approximately offsetting the other. In a steam pipe of proper 
diameter, under given conditions, the frictional loss should be not more than one- 
fifth the loss from radiation. Condensation may be reduced by carefully covering 
the piping with good non-conducting material, but even with the best covering the 
effective pressure at a distant underground engine is greatly diminished, and very 
uneconomical working is the result. In conveying steam a distance of several 
thousand feet, as is by no means uncommon in extensive collieries, the pressure 
may be reduced to half the boiler pressure, or even less. Take, for example, a 
pump situated 2,000 feet from the boiler and using 200 cubic feet of steam per 
minute at a boiler pressure of 75 pounds, with a mineral-wool covered pipe, 4 
inches in diameter, the effective pressure at the pump would be only about 58 
pounds, or, with a poor covering, like some of the asbestos lagging often used, 
it might easily be as low as 35 pounds. For compressed air transmission the 
reduction of pressure for the same volume of air, size of pipe, and initial pressure, 
would be 9.3 pounds, giving a terminal pressure of 65.7 pounds. But, as the speed 
of flow in pipes for economical transmission is greater for steam than for air, a 
comparison based on piping of the same diameter cannot justly be made. If, in 
the above example, the diameter of pipe were smaller the gain in reduced radiation 
would outweigh the increased frictional loss, and the net loss would be diminished. 
The frictional loss varies inversely, and the loss from radiation directly, with the 
diameter. Therefore, under given conditions, the diameter of the pipe can be so 
proportioned as to produce a minimum loss. With compressed air transmission, 
however, the case is dift'erent. For, if the diameter of the pipe in the above case 
be increased to 5 inches, the loss of pressure, or head required to overcome fric- 
tion, is reduced to 2.8 pounds, and increasing the distance to one mile it would 
be only 7.4 pounds. Furthermore, the increased cost of the larger air-pipe would 
be offset by the expense of the non-conducting covering. No account has been 
taken here of the loss due to leakage. Attention may be called to the fact that 



826 USE. 

little or no danger is to be apprehended from the rupture of a compressed air pipe, 
while the bursting of a steam pipe in a shaft or in the mine workings may be a 
serious matter. — Western Mining World. 



COMPRESSED AIR IN UNDERGROUND WORK. 

So much has been said regarding the use of compressed air in mining, that 
very little is left to be said. But I find that with all the information scattered 
from one end of the continent to another, there are a number of mining superin- 
tendents and foremen, in the Western mining country particularly, who are ready 
at all times to argue against its use. Their arguments are sometimes reasonable; 
for instance, when the question of expensive fuel comes up. But most of their 
arguments are unreasonable, and to prove this, we will commerce with rock 
drills, and where they can be used economically ; sinking shafts and winzes, driv- 
ing drifts and upraising, and in a large majority of cases for stoping. 

In sinking by hand, a good day's work for three men would be the drilling 
and blasting in medium hard rock of four holes three feet deep each. These 
four holes would just about make the sump two feet deep; the other two shifts' 
work, if working eight hours each, would hoist the debris and drill the holes to 
square the shaft, making in depth two feet in 24 hours. Had a compressed air 
rock drill been used for this work, all the holes necessary for blasting the bottom 
of a shaft 8 or 9 feet long by 5 feet wide, could be drilled in one shift of 8 hours ; 
and instead of taking out a sump to square two feet, as done by hand, the ma- 
chine in the time stated would drill the holes deep enough to take out a sump 
to square four feet — doubling the work at an extra cost of an engineer and the 
fuel ; or, in other words, instead of sinking 45 to 50 feet per month by hand, 90 
to 100 feet would be sunk with machine drills, and I think shows conclusively the 
economy of their use. 

But with facts of this kind presented, we are told they are not economical, 
and the reasons given are that sinking by machine drills break out too much of 
the sides or walls of the shaft, requiring a great deal of filling and wedging be- 
hind the timber, and in blasting the debris was thrown so. high up the shaft that 
it cut out the dividing timber, and the time lost in the filling and repairing the 
shaft would more than offset any time gained by using machine drills. 

To disprove these statements we would ask, why should the holes drilled by 
a machine have a greater burden to remove than a hole drilled by hand ? and with 
the same judgment used in planning or marking out the position of the hole to be 
drilled, the same results should be obtained and all the holes necessary to make 
the sump and stope holes to square the bottom would be done in one-third the 
time; showing a saving of not less than one-half the cost of drilling compared 
with hand labor. But experience shows that the holes should be drilled by a ma- 
chine with a greater burden, for the reason that the diameter of the hole is much 
larger than a hole drilled by hand; and (as an illustration) where a hole is drilled 
by hand, say 4 feet deep and i inch diameter, and in the opinion of the miner 
charging the hole, he should insert powder enough to fill it up one foot to re- 



USE. 827 

lOve the burden and prevent the breaking out of the sides and cutting out the 
dividing timber. Now, if a machine hole be drilled with double the burden, the 
same depth and about i 3-8 inch diameter at the bott&m, one foot of powder would 
be about double the quantity there would be in the hand-drilled hole; and if the 
resistance is double in the machine-drilled hole, why or by what cause, providing 
the hole was practically pointed, should this hole break further into the walls of 
the shaft, or throw the debris up the shaft to cut down the timber? The only 
answer that suggests itself is : If any difference in results was shown, it was not 
because the hole was drilled by a machine, but for this reason : the hole or holes 
were improperly pointed, or the charge of powder was too great to remove the 
burden in a safe and economical manner. 

If this is correct, is it not economical to use machines? Aside from this, 
you have the benefit of ventilation. The work done in one-half less time, the 
benefits derived from this in most cases is worth to the mining company one-half 
the actual cost of sinking the shaft. 

No one questions the economy of the rock drill in drifting and raising and 
in stoping. 

East of the Missouri River, in Africa and Great Britain shaft sinking is 
done successfully by machine drills operated by compressed air, and there is no 
reason why every shaft in the United States that requires drilling should not 
adopt the rock drill and use of compressed air. 

Many advantages are also gained by compressed air for pumping; no con- 
densation of steam, no change necessary in the pump for its application. Mine 
timbers are kept dry and preserved. It prevents arches and pillars in the mine 
from slacking and crumbling; can be applied to small hoists for hoisting the 
debris out of winzes, raising timber, etc. 

Many mines have soft or what is termed running ground, very difficult to 
timber. If in drifting the breast has to be close timbered in sections, the ad- 
vancement is very slow. A great deal of tim<? can be saved by putting in an air 
lock and using 30 to 40 pounds pressure of air. This will in most cases allow the 
miners to advance very rapidly and far enough for a set of timber, and the set 
of timber put in in the ordinary way. The cost of a lock in a small tunnel would 
be no more than the extra cost required for timbering such ground as above 
described for the advancement of 6 feet of three sets of timber in the ordinary 

way. WM. M. TREGLOWN. 



Charlestown, Mass., Aug. 6th, 1897. 
Compressed Air: 

Some experiences in connection with the early use of compressed air at the 
Hoosac Tunnel may be amusing if not instructive. 

It was clearly understood by those who were devising and building com- 
pressors and drills, that steam could not be used in Tunnel work. 

The drills were simple and strong machines, the Burligh type being the 
first and, I think, the only ones there. 

In the very beginning it was determined to put the drills in charge of the 
foreman of miners, instead of introducing a new element in the way of skilled 



828 USE. 

or even common mechanics, with whom the other men would have no sympathy. 
It was thought more important to have men, who, through their experience, 
knew how to place holes which would do the most work, than to have men 
ignorant in this respect, though, familiar with the construction of the drills, 
which they could scarcely injure. This plan proved successful, and secured har- 
mony all around. 

But even while using compressed air, at the east end there were many who 
believed that steam would do just as well. In order to convince such, and se- 
cure uniform belief on this subject, it was determined to make the trial. 

A point was selected which was as near out of doors as any thing on the 
work, the central shaft. This was an ellipse in form, its axis being 27 and 15 
feet respectively. 

It was then down 74 feet from the surface. There were no means of com- 
pressing air at this point, but there was an engine of 100 horse power for hoist- 
ing, and 3 boilers, set up and in working order. So a drilling machine intended 
to be used with air was set up on its tripod and the work begun. The escape 
steam was carried by a rubber hose into the water in the bottom of the shaft. 
The hose was shifted about from puddle to puddle, until all the water became 
boiling hot, and it became a very serious question where to find standing points. 
When the water under foot would take no more steam, it must of course take to 
the air, which soon became so thick that a man could not see his hands before 
his face, nor find air enough to breathe. 

In addition to this, the drills of course could not be directed aright, and 
they also became so hot that they could not be handled. 

So by this simple and inexpensive trial, everybody was convinced, and no 
more talk about it was heard. 

As in much of this world's experience, "seeing is believing." 

THOMAS DOANE. 



VENTILATION OF THE ST. GOTHARD TUNNEL. 

Up to the year 1890 the differences of air pressure in the two ends of this 
double line tunnel (length g% miles), and the resulting through current of air, 
was sufficient to keep the atmosphere pure enough for platelayers to work com- 
fortably in, but after that date the traffic increased so much that it became neces- 
sary to resort to artificial ventilation, and in March of 1899, a complete plant on 
Saccardo's system was set in operation to effect this object. 

The installation, which is situated at the north end of the tunnel, consists 
of a locomotive driving two fans, each five metres (16.4 ft.) in diameter. These 
fans compress air into a chamber surrounding the face of the tunnel, from whence 
it issues through an annular aperture and in a southerly direction along the tun- 
nel, dragging the mass of air in the body of the tunnel along with it, on the same 
principle as the steam injector. 

Since the plant has been in operation the air in the tunnel has been pure 
and free from smoky smell, and besides facilitating the work of platelaying and 



USE. 



829 



inspection it is expected that the permanent way will have a longer life under 
the new conditions. The cost of the installation, exclusive of the locomotive, was 
about £7,200. 



COMPRESSED AIR DREDGER FOR GOLD MINING. 

In general, as shown above, these machines are iron caissons, which can be 
raised or lowered through the center of a boat or barge, the water being expelled 



f^ :<^s 



I 



\\ 









a! 



'i 



'% 



\\\ ^^^ P^ffi_:- 




'■Mi>fimm^m<^ 




I 



FIG. 313. — SUBMARINE GOLD MINING MACHINE. 



by the proper pressure of compressed air. The bottom is thus exposed to the 
direct manipulation of the miner who is within the caisson, and he picks or other- 
wise loosens up the earth or gravel on the bottom and sends it to the surface 
through the small internal discharge pipe, either by direct air or water pressure 
as he desires. 



830 USE. 

This apparatus consists of an air compressor and appurtenances for operat- 
ing it. The equipment being very complete with telephones, traps, pipes, ejectors, 
etc. 

This machine does not interfere with the dredgers, the idea being to clean 
up the bedrock in the cracks and crevices wherein lie the heavy gold which no 
dredger of any kind has ever been able to lift. Dredgers working on rivers have to 
stop when they have cleared off the upper portion of the bed rock. They cannot 
go into the holes or crevices. 

No bad effects upon the operator are produced as the pressure is moderate 
and invigorates rather than depresses the worker. 

Men work in caissons at 25 to 30 pounds pressure per square inch, which 
corresponds to 60 and 70 of water pressure. 

This machine is intended for such rivers as the Yukon and is manufactured 
by Rix & Donahoo, San Francisco. 



ELECTRICITY IN MINING.* 



It has already been pointed out that electric percussion drills have not so 
far been at all successful. Two principles have been made use of in these drills, 
some deriving their reciprocating action from the sucking power of solenoids, 
others striking a blow under the action of a spring, which is compressed by a 
cam, and, when released, allowed to shoot the drill forward, or else, actuating the 
drill by some form of crank; that is to say, the latter class convert the rotary 
motion of the motor into a reciprocating movement. Solenoid drills, of which the 
Van Depoele and the Mavin are examples, have not proved satisfactory, the main 
difficulties being the treating of the coils of the solenoid and want of power in 
the blow. Mavin drills have been used in one or two places, but no accurate 
data as to the results obtained are available. The solenoid drill made by the 
Union Electricitates Gesellschaft strikes 350 to 500 blows per minute, requires 4 
h. p., and is said to drill about two inches per minute. The Bladray drill is one 
of the neatest forms of the second type, spoken of sometimes as electrical 
mechanical drills. In this drill the drill stem is encircled by a cylindrical cam 
which forms the continuation of the hollow armature of a small motor. The 
cam works against a scroll-shaped cylindrical tappet, which is a portion of the 
drill stem, and is pressed forward by a powerful spring. As the cam revolves 
the tappet is pressed back against the spring till it clears itself, when the spring 
shoots it forward, striking the blow. This drill strikes 700 3-inch blows per 
minute, and has been used in South Africa; but nothing is yet known of the 
results obtained by it. Messers. Siemens and Halske make a percussion drill 
very like the Ingersoll hand drill, fitted with a heavy flywheel, and worked by 
means of a separate motor, the cam of the drill and the motor being connected by 
a flexible shaft. This machine strikes 450 blows per minute, and is said to be 



Scienc*e^^ewcS,e'i'n"T>?e. ""' ""' ^' ^' ''" ^^ ^^ ^^ ^*^-' P^ofeesor Mining. Durham College of 



USE. 831 

capable of boring a i>^-inch hole into hard granite at the rate of 4 inches per 
minute with the consumption of i h. p. It need hardly be said that if these 
results can really be obtained in practical work it would be a most valuable 
machine, and far more efficient than any compressed air drill. It has hardly yet 
passed beyond the experimental stage, and is, moreover, a cumbersome and 
clumsy machine. A more modern type is the Bornet drill, which has been used in 
the south of France. This drill is actuated by a separate motor, the connection 
between the two being by means of a flexible shaft on a double Hooke joint; 
this works a crank shaft, the crank moving a solid piston backwards and for- 
wards. The piston is enclosed in a cylinder, to the front cover of which the 
drill is attached; the action is thus precisely similar to that of the Scoll pneu- 
matic stamp, the air compressed alternately in either end of the cylinder acting 
as a spring and giving the machine the required elasticity. As already said, elec- 
tric percussion drilling is, as yet, very far from being a success. 

Rotating electric drills have given excellent results wherever they are 
applicable, which is, of course, only in the softer rocks, such as ironstone, salt 
and coal. One of the best of these drills is that designed by Mr. A. A. Steavenson 
and made by Messrs. Easton, Anderson & Goolden (Limited), for use in the iron- 
stone mines of the Cleveland district. It consists of a carriage supporting a 
standard capable of being turned in any direction, which carries an arm, on one 
end of which is supported a small direct current motor, whilst the other end 
carries a twist drill driven by means of bent gearing, the connection between the 
drill and its driving shaft being made by a Hooke joint, so as to allow the drill 
perfect freedom of motion. Such a drill works at 220 volts, and requires 20 
amperes, or (say) 6 h. p. at the drill. It makes 100 revolutions per minute, and 
drills in ironstone at an average rate of 3 feet to 4 feet per minute ; in a working 
shift of ten hours each drill will put in 100 holes, averaging 4 feet to 5 feet deep, 
in about eight different working places. Messrs. Siemens & Halske make a 
twist drill, worked from a separate motor by means of a flexible shaft. It is 
used in the salt mines of New Stassfurt, where it has given good results; its 
rate of advance is controlled by differential gear. The motor is of i to 1.5 h. p. ; 
the drill makes 200 revolutions per minute, and drills about i foot in depth in 
from I to 2 minutes. The General Electric Company makes an electric twist 
drill connected directly with the motor. It absorbs 2 h. p., makes 300 revolutions 
per minute, and drills i foot in depth in 30 to 40 seconds. These machines are 
quite effective for boring in coal, for which purpose the Jeffrey drill is particu- 
larly well adapted on account of its lightness, portability and compactness. It 
works at 220, 350 or 500 volts, and will drill to a depth of 6 feet in about a minute. 

Electric motors present quite special advantages for working diamond 
drills, and have been largely used for that purpose, both at surface and for 
explorations underground. A drill working a 2-inch hole and bringing up a i^- 
inch core, capable of drilling easily to a depth of 600 feet, can be driven by a 2^-h. 
p. motor, the whole arrangement being compact in the extreme and suitable for 
prospecting underground or in awkward situations where steam could hardly be 
used. The only rival that electricity has to compete with under such conditions 
is the oil engine, and it is obvious enough that the latter has many serious draw- 
backs, especially underground. The rapid rotation of the diamond drill renders 



832 USE. 

it particularly suitable for electric drivage. Were it not for the prohibitive price 
of the diamonds required, it is probable that electrically driven diamond drills 
would have been used extensively before this for drilling shot holes, and, as 
already said, it needs only the discovery of a suitable substitute to place this 
mode of boring high amongst the most important of mining appliances. 

Electric locomotives have been used a good deal in America, and also on 
the Continent of Europe. Some are worked by means of secondary batteries, 
but the majority take their power off wires running along the roof or sides of 
the drift. Except in fiery mines, no more convenient or economical method of 
haulage can be devised where large quantities of mineral have to be transported 
considerable distances, whether underground or on the surface. Electric locomo- 
tives have been built by the Jeffrey Company, the General Electric Company, 
Messrs. Siemens & Halske, and others. These locomotives usually run at from 200 
to 400 yards per minute, and can ascend grades of 5 per cent. When this inclina- 
tion is exceeded, rope haulage is generally preferable. In addition to the general 
advantages of electricity over steam underground, the electric locomotive has 
that of great compactness combined with ample power, electric mine locomotives 
capable of developing a drawbar pull of 10,000 lbs. having been built and worked 
successfully. Polyphase motors have been used, but most locomotives are worked 
with continuous current. The useful effect of an electric locomotive is usuallly 
70 per cent, of the electric power in the conductors, expressed in terms of draw- 
bar pull. Mine locomotives are usually of 10 to 15 h. p., the weight of the former 
being about 2j/^ tons; but in special cases much larger and heavier locomotives 
are employed. As has already been pointed out, underground traction by means 
of electric locomotives presents practically the same problems as does ordinary 
traction at the surface, and is, therefore, rather a matter for the electrician than 
for the mining engineer. 



IMPROVED QUARRY PLANT. 



During the past year the Washington Slate Co. has been quietly experi- 
menting on the practical application of compressed air as the motive power for the 
operation of their quarry and factory plant, and it is claimed by the manager, Mr. 
A. P. Berlin, who designed and built the plant and conducted the experiment, that 
it has proven not alone successful, but has exceeded his highest expectations. 

This plant is not only a novelty because it is the only successful one of 
the kind in the world to-day, but also on account of the general effect noticeable in 
the quarries and about the works by reason of its entire absence of condensed 
steam and smoke. Every quarry man will understand and fully appreciate the 
importance of having the quarries relieved of the heavy clouds of vapor and 
smoke which so often hang over the opening when the outside atmosphere is 
heavy. 

The power plant is located on the Company's private siding connected with 
a branch of the Lehigh Valley Railroad and consists of one Return Tubular 
Boiler of 140 horse power, with a return draft and a nest of two reserved boilers 



USE. 833 

of 90-horse power so connected with the main boiler and the machinery that either 
one or both can be used in running the plant. 

The Air Compressor is an Ingersoll-Sergeant, Straight Line, Class "A" 
machine, with piston inlet valves and automatic unloading device and all the 
latest improvements. The steam cylinder is 18 inches in diameter and 24-inch 
stroke, and the air cylinder 20^4 inches in diameter and 24-inch stroke, capable of 
developing 127 horse power with 90 revolutions per minute and 60 lbs. air pres- 
sure. Total weight of compressor, 20,400 lbs. 

The plant has all the necessary side equipments, consisting of air receivers, 
water tank, feed and supply pumps and a unique system of pipe and valve co;i- 
nections by which the steam direct from the boilers can be substituted for the 
compressed air and the compressor put out of service in case of emergency or 
accident, without closing down the operations. 

The main supply of compressed air is delivered through a 5-inch pipe to 
the quarries 1,000 feet from the power plant. The quarry plant is operated solely 
by compressed air, and consists at the present time of two Double Drum Flory 
Hoisting Engines for three cable ways, and one small hoisting engine operating a 
swing derrick, one duplex pump, two air drills and one small stationary engine 
which supplies the power for two slate sawing benches and two sets of school slate 
saws. 

Besides the quarry operations, this plant supplies the power for the running 
of two slate factories, with a 30-horse power stationary engine in each one 
located 75 feet from the compressor, and the other at a distance of 300 feet. — Slate. 



THE POWER PLANT OF GOLDEN WAVE MINE, CONGRESS, ARIZ. 

A most interesting installation of an air compressor, a gasoline engine and 
a mine hoist, is afforded by a plant installed at the Golden Wave Mine, Congress, 
Arizona, and as an example of the cost the following information is given : 

The speed of the compressor is 175 revolutions per minute. 

The size of heading, 10' x 8'. 

Elevation above the sea level, 6,000 feet. 

Ten holes are put down to each round, i^" diameter x 5' deep. 

Two rounds of holes are drilled and blasted each shift of 10 hours, making 
7' progress per shift, or 14' per day. 

It requires 6 lbs., of No. 2 Giant powder for each round of holes, or 24 lbs. 
to 14' of tunnel, or 1,714 lbs. powder per lineal foot of drift. 

The following force is employed underground: 

Four drillers per shift, making eight per day, with wages $3.50 per day 



each. 



One mucker per shift, or two per day, at $3 each. 
Number of cars hoisted per shift, 25. 
Cars waste, 15. 
Cars, ore, 10. 



834 USE. 

Weight of loaded car — ore i,SOO lbs. 

car 500 " 

Total 2,000 lbs. 

Total output per shift, 37,500 lbs. 
" " day, 37H tons. - 

Gasoline, per shift, 9 gallons. 
" day, 18 " 

Cost of gasoline per day, $2.70. 

Number of men above ground ; two each shift, four per day, at $3.50. 

Drills operate about 2^/2 hours per shift, or five hours per day. 

Time to drill one round of holes, iJ4 hours. 

Ground hard and flinty, 1-3 harder than Chicago Tunnel work. 

Hoisting, incline, 30% ; 380' to heading. 

Time hoisting, i^ minutes. 

Feet tunnel per day, 14. Gasoline, $2.70. $0.1928 per loot. 

Eight drillers, at $3.50 $28.00 

Two muckers, at $3.00 6.00 

Four men above ground, $3.50 14.00 

$48.00 

$48.00 labor for 14' ; per foot $3.43 

Gasoline, per foot 1928 

Cost of labor and fuel per ft. of drift $3.6228 

This is a practical demonstration of the cost of operating such a plant and 
those who are working small claims now by hand will find a plant of"this kind 
one that can be installed with small outlay and at the same time obtain results 
possible only with machine mining. 

We are enabled, through the courtesy of Messrs. Patterson, Gottfried & 
Hunter, of New York, the general Eastern agents of the Fairbanks-Morse Co., 
to give to our readers the following accurate description of the plant itself, which, 
when taken in connection with the foregoing data, should prove of interest. 

The gasoline engine is a standard Fairbanks-Morse engine of 30 B.H.P., 
and is located between the air compressor and hoist. The shaft of the compressor 
\z directly connected to the engine shaft by means of a friction clutch coupling 
which permits of the disconnection of the compressor at will. When the com- 
pressor is not required it may be totally uncoupled from the engine, thereby allow- 
ing the use of the available power for hoisting. 

The compressor is fitted with a mechanical unloading device, which, when 
the desired pressure has been attained holds open the admission valve and pre- 
vents compression. When this unloading occurs the load on the engine is imme- 
diately reduced and the governor automatically cuts down the supply of fuel in 
proportion to the demand for power. 

The usual forms of Fairbanks-Morse gas engine air compressors met with 
are either a direct connected outfit in which the air cylinder and engine cylinder 
are mounted on the same frame having a common shaft, and secondly the familiar 



USE. 835 

belted unit. In the plant in question, however, the conditions were such that 
neither of the above combinations would answer, and it was found necessary to 
especially devise this direct driving arrangement with the intermediate clutch 
coupling so that they could be used intermittently. 

The hoister employed is known as a flat faced friction hoist. On the oppo- 
site side from the compressor the engine shaft is extended to receive two flat 
friction rollers; these rollers bear on two iron surfaces which form the sides of 
the rope drum, the rollers thus acting on either side of the drum. The drum is 
carried on two eccentric boxes and its movement horizontally is controlled by a 
lever which works in a quadrant. When it is desired to operate the hoist the 
drum is shifted into contact with the friction rollers by manipulating the control- 
ing lever and the drum is made to revolve. 

In connection with the hoisting part of the apparatus the engine is equipped 
with an automatic speed regulating device. A foot pedal is conveniently placed 
which communicates with the governor, and when no pressure is exerted upon it 
the engine runs at a minimum speed of approximately 70 revolutions per minute. 
This pedal being pressed down, however, immediately increases the speed of the 
engine to normal. The object of this speed variating device is two- fold; first, the 
chances of accident are greatly reduced, for, immediately the pressure on the pedal 
is removed the power and speed of the engine is cut down to a minimum and 
second, the speed being cut down when the hoist is not in use greatly reduces the 
consumption of fuel during the periods of idleness. 

Another feature which may be of interest is the fact that power is used only 
in hoisting; while lowering, the power is cut off and the drum is controlled by 
means of a band brake. 

The compressor is constructed with opening for air intake, so arranged as 
to connect with cold air outside of engine room, air arriving as cold as possible 
within the cylinder. The cylinder and head of the compressor are water jacketed, 
relieving the air of much of the heat due to compression. The air cylinder is 
single acting, doing away with stuffing box and having only one set of valves, 
which are easily removed together with their seats. 

This plant tends strongly to confirm the many advantages of the gasoline 
engine for mining, and especially is the fact made clear that great economy may be 
expected from a gas engine air compressor combination, for, where other fuels 
are scarce gasoline is generally easily obtainable owing to its portability, and 
this fact coupled with the portability of the machine itself and its general com- 
pactness render the gasoline engine invaluable for many purposes. 



THE USE OF COMPRESSED AIR IN BUILDING THE DELAWARE 

BREAKWATER. 

Among recent appropriations made for river and harbor improvements by 
the United States Government was an appropriation of $4,665,000, which pro- 
vided for the construction of a harbor of refuge for deep draft vessels in Dela- 
ware Bay, and is expected to be completed on or before December 31, 1901. 



836 



USE. 



GENERAL PROJECT. 

The plans submitted by the chief of engineers, January 29, 1892, which 
were adopted by Congress in the Act of June 3, 1896, are contained in the report 
of a commission of engineer officers, dated January 5, 1892, and published in 
Document No, 112, House of Representatives, 52d Congress, ist Session. They 
provide for the construction of a stone breakwater located upon the line of least 
depth along the eastern branch of the shoals known as the Shears. This shoal 
is situated upon the west side of the main ship channel near the entrance of 
Delaware Bay. It is proposed to form the breakwater by the deposit of random 
stone to the level of low water, and by the construction of a superstructure 




FIG. 314. — THE USE OF COMPRESSED AIR IN BUILDING THE DELAWARE BREAKWATER. 



thereon, by the erection of outer and inner walls of very heavy stones, the in- 
terior space to be filled with rubble. 

The total length of the breakwater at the level of mean low water will be 
about 8,000 feet, but this length may be increased if found practicable without 
increasing the quantity of stone estimated for the construction of the work. 

The depth at mean low water along the site of the work varies from 13' 
to S3', the average depth being 28'. 

It was assumed that each cu. yd. of enrockment will contain 1.25 gross tons 
of stone. Upon this assumption, the approximate amount of stone to be quarried 



USE. 837 

for the construction of the breakwater, expressed in tons of 2,000 lbs. each, is as 

follows : 

Substructure 1,210,665 

Superstructure ^^73,7 45 

Total 1,384,410 

The site of the proposed breakwater is about 254 miles north of the Dela- 
ware breakwater harbor, about 3 miles from the Government pier at Lower 
Delaware, and about 10 miles from Cape May. 

The contract for the complete work was let on Dec. loth, '96, to Messrs. 




FIG. 315. — MCMYLER DERRICKS. 



Hughes Bros. & Bangs, of Syracuse, New York, and is one of a number of 
large contracts on public works now in hand by this firm. 

The work of laying out a plant for this immense work was begun soon 
after the awarding of the contract, and at the present time the work is pretty 
well under way, the output at the present time being just about 50 per cent, of the 
proposed total capacity. 



838 



USE. 



Suitable stone in sufficient quantity was found at Bellevue, Del., a station 
on the P. W. & B. R. R., and located on the Delaware River, about 5 miles from 
Wilmington, or a distance of 75 miles from breakwater. At this point a large 
dock has been constructed, and ample facilities are at hand for handling an output 
of 3,000 tons of stones per day. 

Connecting the dock with the quarry is one mile of double track railroad, 
built of 6o-lb. steel rail, and has stone ballast laid on a 2 per cent, grade. A num- 
ber of cross-overs, or sidings, are provided, so that loaded and empty trains may 
pass each other. 

Four Baldwin locomotives (Fig. 320), with cylinders 12 x 16, handle the 
various mixed trains of flat cars and gondolas. The train equipment consists 




:i&?;K-?^. 



FIG. j:^ 1 6.— AIR COMPRESSOR. 



of 300 flat cars, 15 tons capacity, and 60 gondolas, 10 tons capacity each (for 
earth and small rock). 

When a train load of stone reaches the dock it is run on one of the sidings, 
the locomotive taking back the empties, and two derricks, provided each with 
Bull wheels, as shown on cover, unload the stone from cars to the barges; 2 
hoisting engines operate the derricks, and each Bull wheel is controlled by a 
small rotary engine operated by compressed air. 

The water-way equipment for this plant consists of 13 barges, each 180 feet 
long, with 40 feet beam ; 7 of these barges have flat decks and are fitted with 
steam derricks, and the other 6 are known as open bottom dump scows. The 
capacity of each barge is 1,500 tons. 

There are also 3 ocean tugs, .110 feet long, that tow the barges from 
Bellevue to the breakwater, each tow consisting of 2 barges, and takes about 6 
days to make the round trip. 



USE. 



839 



The quarry equipment proper consists of 9 McMyler Derricks; 20 Inger- 
soll-Sergeant Rock Drills, 3^" cylinder; 12 Lidgerwood Hoisting Engines for 
operating 22 derricks, and several small pumps for draining quarry. 

The McMyler derricks, as shown in cut (Fig. 315), are fitted with steam 
cranes, run on 16 feet gauge track, and have a capacity of 15 tons at 30 feet 
radius, or 6 tons at 45 feet radius. The rock drills are of the standard Sergeant 
and Tappet make of the Ingersoll-Sergeant Drill Co. 

The hoisting engines are 8j4" x 10" double cylinder, double drivers, so 
roped as to handle stones from 12 to 15 tons. 

The question of operating so large a quarry plant as this in the most 
economical manner was thoroughly considered by the contractors. Estimates 




FIG. 317. — POWER HOUSE. 



were received for electric transmission, compressed air and steam transmission. 
A visit to Jerome Park, where similar work is being done from a compressed 
air central plant, soon convinced the contractors that for work of such variable 
nature as this the Central Compressed Air Power Plant gave the best assurance 
of economy, and it was therefore installed. 

The compressor is one of the best type made by the Ingersoll-Sergeant 



840 USE. 

Drill Co., of New York, and has compound steam and air cylinders of the fol- 
lowing dimensions : 

High pressure steam cylinder 22" x 48" 

Low " " " 40" X 48" 

Low " ,air " 36^" x 48" 

High " " " 22K" X 48" 

The air cylinders are tied tandem to a Corliss Compound Condensing En- 
gine, and are also connected by a vertical receiver intercooler, 48" diameter by 
13' 6" high (Fig. 316). The air pressure is steadily maintained at 80 to 85 lbs. 
at power house, and Fig. 317 shows location of power house. The pond shown 




FIG. 318. — COAL-BIN 600 TONS CAPACITY, AND FLAT DECK BARGE 1,500 TONS CAPACITY. 



in cut has an average depth of 14 ft., and is of sufficient area to maintain 
a low temperature for the condensing water which is used over and over. The 
coal is first stored in a 600 ton bin at the dock (Fig. 318), and carried as required 
by dump cars upon inclined track to bin of 300 ton capacity at boiler house 
(Fig. 317). 

The boiler plant consists of 3 Hogan water tube boilers (Fig. 319) of 125 
horse power each, and furnish steam to the compressor at 125 lbs. per sq. in. 

One fireman is all that is required at the boilers, and the compressor 
receives the attention of only one man, the engineer; so that aside from the old 



r 



USE. 



841 



method of carting the coal to the various small boilers about work of this kind, 
and the expense thereof, there is quite a saving effected in labor for attendance, 
to say nothing about the difference in producing a given amount of power by an 
economical Corliss engine, situated convenient for water and coal, as compared 
with a number of small boilers carrying steam through long, uncovered pipes, 
and where the boilers are constantly in danger of being damaged by flying stones, 
thus making the question of repair account an important one when compared with 
the central power plant. 

Aside from these questions of advantage, it will be well to bear in mind that 
the compressor is fitted with an automatic unloading device which unloads the air 






FK.. Jiy. — THKEE HOGAN BOJLEKS. 



cyclinders as soon as a maximum pressure of 85 lbs. lias been reached, thus calling 
for only enough steam to overcome the friction of the compressor. When the 
pressure in pipe line falls to 80 lbs., the unloading device responds and the machine 
goes on with its regular work. 

When rock drills use compressed air, the drill is capable of drilling more 
feet per day than with steam, due to higher pressure (because of no condensa- 
tion), and the drills are easier handled by the operator on account of being cold. 
Again, a given quantity of oil will do more service in an air motor than in a steam 
motor, for there is less heat to destroy the useful effect. 



842 



USE. 



The convenience of having air power on tap at this quarry is illustrated in 
its use in the various pumps which are set to work intermittently and at any place 
without the delay of changing boilers and keeping them partially fired. Drinking 
water of the finest quality is drawn from a well 200 ft. deep, by means of a Pohle 
Air-lift Pump, a device calling for but 2 long pieces of pipe, and has no valves to 
get out of order. 

Up to the present time there has been no trouble due to freezing of the 
moisture contained in the air. However, if trouble should arise from that source 





^^^PW^^< 


*|" 


flW-'^^jff' _■■ ^ . ■ .... .-. 




-~ -^^^r^!^™^"™ ' 



FIG. 320. — LOADED TRAIN. 



in winter, small reheaters will be placed near the various motors, which are quite 
inexpensive to maintain and have the good grace to add about 30% to the effi- 
ciency of the plant when used in the proper manner. 

This is practically the second large plant of this kind in this country, and 
we venture to predict the establishment of more; for the results obtained are so 
far in advance of old practice, that it would be folly to go back. 

F. C. Weber. 



!^-,- 



USE. 



843 



THE COMPRESSED AIR POWER PLANT AT JEROME PARK, N. Y. 

The Aqueduct Commissioners of the City of New York have now in 
active progress of construction two important works to increase the water sup- 
ply of New York City. One is the new Croton dam, designed to increase the 
size of the present Croton Lake and thereby impound a greatly increased water 
supply for the city at large. 

From the present Croton Lake two aqueducts, the old one of 1840, the 
other the new one completed in 1890, run to the city, delivering their water di- 
rectly into the reservoirs in Central Park. The city of New York has had one 




FIG. 321. — THE POWER PLANT — JEROME PARK, N. Y. 



policy as to its water supply; it has always worked on the lines of an increase 
of reservoir capacity by addition, the old reservoirs being preserved. 

To provide for additional storage capacity for direct use in the city, con- 
struction operations are now in progress on what is known as Jerome Park 
reservoir, in Fordham, in the annexed district. 

Here Jerome Park, with its famous old race course on which so many 
celebrated horses have been ridden to defeat or victory, with a quantity of adja 
cent territory, has been selected for a reservoir. The ground offers fair ad- 
vantages in point of elevation and configuration; its vicinity to the city and its 
situation in the heart of the annexed district make it peculiarly available for the 
purpose. The area of about 5,800 feet long and 2,800 feet wide is to be sur- 
rounded by an embankment and the bottom is to be excavated until good surface 
is reached, so as to establish an available depth of 33 feet 6 inches. This will 
involve a very large amount of excavation ; the engineers having estimated that 
there will be nearly seven million of cubic yards of excavation to be made, of 
which 3,165,000 will be in solid rock. 



844 



USE. 



The reservoir will be bounded on the west by Sedgwick avenue, on the 
east by Jerome avenue, north by Van Cortlandt Park, and south by Kingsbridge 
Road. 

Mr. John B. McDonald secured the contract for building the reservoir in 
August, 1894. He examined the various methods for facilitating the work and 
doing it economically. Being a man of practical methods, he went into the 
examination with great thoroughness, and finally decided that he would adopt 
the compressed air central plant system as the most efficient and economical. 

The plan is to locate a compressor at a central point, compress the air 
into a large storage receiver and from thence conduct it in pipes to wherever 
it is needed. Consequently a plant of this kind was procured. An 8-inch pipe 
is laid from the storage tank and takes a straight course to the northeasterly 
corner of the work. 

This pipe is tapped at various points, and each lateral supplies air to 
drills and other apparatus. These drills, hoists, pumps, etc., are located in 




THE QUARRIES, 



various parts of the tract. They may all be in use at one time if occasion requires 
it, or only one machine need be in use. This distribution of air power on the 
"European plan" has effected some wonderful economies. 

There are 14 rock drills, 14 hoisting engines, and 3 water pumps at work 
during the day. They are supplied by power from the central plant, which con- 
sists of one Ingersoll-Sergeant Duplex Corliss Condensing Air Compressor, 
steam cylinder 24 and 44 x 48; two air cylinders, 24^ x 48, capable of produc- 
mg 540 H. p. at a pressure of 80 pounds at the air receiver. Steam is made for 
this compressor by a Hogan Water Tube Boiler, manufactured by the Hogan 
Boiler Co. of Middletown, N. Y., the nominal rating of which is 240 horse power. 
The pipe leading from the receiver is 8 in. in diameter and carries the main sup- 
ply of air to the individual machines. At a distance of 2,000 feet the air passes 
through a Sergeant Reheater. This reheater consists of two cast iron shells, 
which are bolted together. In appearance it resembles a truncated cone. It 
keeps the velocity of the air constant. The air being hot, it has greater volume, 
and would consequently increase the friction if there was no room for expan- 



USE. 



845 



ion. Tests have been made with this heater, and the results show that 340 
ibic feet of free air per minute, at 40 lbs. pressure, can be reheated so that a 
lin of 35 per cent, is imparted to the energy of a pound of air. 

The point where the economy is immediately effected is in the operation 
the drills, hoists and pumps. Ordinarily these would be run by separate 
boilers requiring the attendance of an engineer and stoker, and the extra labor 
of hauling fuel and water to each boiler. This performance is dispensed with 
by the air power being transmitted from the central station. 

Aside from the reduction in expense, the convenience of having a power 
that can be used at any moment and without the annoyances attending the care 
of individual boilers for each machine facilitate the work vastly. 

The whole work of excavation is reduced to as small a use of human 
effort as can well be devised at this time. 

With the use of steam for the operation of drills, considerable water- 
condensed steam — collects in the pipe, even in the short time consumed in chang- 




FIG. 323. — RE-HEATING THE AIR. 



ing bits or moving from one hole to another. This must be worked out through 
the exhaust before the drill can begin to do good work. If this water from the 
different drills and pumps could be collected, it would be found to amount to a 
great many barrels in the course of a day. Each cubic foot of water wasted by 
condensation represents one horse power. There is another and serious loss 
with steam — that of loss of capacity of the drills. With full pressure of dry 
elastic compressed air at the drills, more work will be done than by the wet 
steam, a less number of drills, drill runners and helpers are required for the 
same work, and these various reductions in the pay roll and coal bill may 
amount to the cost of the plant before it is worn out. It is a common expres- 
sion of quarrymen who have adopted compressed air after using steam, that 
"two drills will do more work with air than three with steam." 

There are several other items, representing in the aggregate a large amount, 
that would be difficult to name, that is saved by the Jerome Park plant. For 
instance, a cheaper grade of hose can be used with air, and will outwear several 
lengths of steam hose. As a matter of fact, quarrymen using compressed air 
find that the saving in hose alone equals the expense of keeping up the plant. 



846 



USE. 



Less oil is required with air than steam. A little oil will last for hours 
in an air oylinder and will ease the working of the jnachine. Steam bums the 
oil out in a few minutes. 

It is evident that greater economy will be realized by the use of one cen- 
tral plant placed where fuel and water are most accessible, removed from all 
danger from blasts, falling derricks, etc., not subject to constant removal, pro- 
vided with an economical boiler plant, a compressing engine of high efficiency, 
fitted with an entirely automatic system of governing devices, using steam ex- 
pansively, and requiring steam only in exact proportion to the amount of air 
being used. This disposes of all annoyance and expense incidental to supply- 
ing coal and water to a number of different boilers, and there is only one fire- 




FIG. 324. — HOISTING A 3 TON ROCK BY AIR POWER. 

man, and one boiler plant to keep in repair. All annoyance and expense from 
frozen pipes in cold weather, smoke, exhaust steam and ashes in the quarry are 
avoided. 



PAINTING BY COMPRESSED AIR. 



IMPORTANT DISCUSSION BY THE NEW ENGLAND RAILROAD CLUB. 

At the February meeting of the New England Railroad Club the subject 
for discussion was: "Is it Economy to Use Compressed Air in Painting 
Railway Equipment?" The facts presented by the various speakers are of such 
a character that they have been widely published and favorable comment has 
been the rule. We reproduce the various interesting parts of the discussion. 
Following are the remarks of Mr. C. E. Copp, general foreman painter B. & M. 
R. R.: 

"I saw and questioned a man who painted the equivalent of 29 standard 
34-ft. coal cars in about five hours, which is an average of one every 10 minutes, 
and the air pressure was poor. Various speeds of from five to ten minutes 



USE. 847 

car were realized at this work. This was for the car body and attachments 

ily. No more material was wasted than by the brush generally. By a test 

ide at the Pittsburg & Lake Erie shops less was used by the spray method. 

lut when computing the expense of painting by compressed air, the cost of the 

air should be reckoned in. Westinghouse air pumps will not answer for all 

these attachments that are being put on the shops ; there must be compressors of 

more power employed. 

"As to the practicability of this method, conditions will vary. As an open- 
air way of painting cars in yards in pleasant weather, I have no doubt of its 
utility, by having the yards, of course, piped with the air, with connections at 
proper intervals. But in very cold weather out of doors it is found that the con- 
densation or dampness of the air in the hose congeals and stops the valves, ren- 
dering them inoperative. To remedy this trouble, some way of warming the air 
by passing it through a heated coil has been considered. My opinion is that it 
will require as much skill, if not more, to operate a spray successfully as by the 
brush method, especially if the machine is at all complicated. And then it must 
be adjusted rightly, held at the proper distance from the work, and not too long 
in one place; for, if it is, it will produce unsightly runs, requiring slicking up 
with a brush afterward. 

"If lead dust from sandpapering is deadly to breathe into the system, 
what may lead mist be from spraying? And so green paint containing arsenic, 
or any other poison. But if cars are painted with an earth paint, as they should 
be, such as mineral brown, which most roads are doing, then no fears need be 
entertained of its poisonous effects. And in this connection I should recommend, 
if this method of painting were adopted, to do the car all over with it, top, body, 
trucks, iron-work and all, and afterward blacK no irons, as they would be much 
more durable that way than with the asphaltum black which is generally applied. 

"As to the quality of work done by the spray method in comparison with 
brush work, it may be thought that the working of a heavy-bodied paint well 
into the pores of the wood by a patient and diligent spreading of the same by 
hand with a brush would be more durable, than the sprayed article, and doubt- 
less it would be if it were done ; but, as a matter of fact, freight cars are not 
painted that way in nine cases out of ten. We know that they are slopped over 
in the most hap-hazard way possible, especially at piece-work prices, the only 
object being to cover them with the paint and a brush, which is often of huge 
proportions, so that the paint runs down the beads and drips on the floor. 

"To the credit of paint sprayed on, it may be truthfully said that it will 
go into places where, with great difficulty, if not impossibility, it is to be put 
with a brush. 

"Regarding the immediate adoption of this method of work, I should 
recommend its postponement, except in the line of experiment, until its patent- 
ability is cleared up, and then only when its practicability was fully settled." 

Mr. Worrall presented the following, which was prepared by Mr. W. O. 
Quest, foreman of painting, P. & L. E. R. R. Co.: 

"We will further call your attention to the fact that a perfectly atomized 
sprayed on paint will almost instantaneously reach, cover up and consequently 
protect a car's most complicated structural parts. It penetrates the rough 



848 



USE. 



beaded work — the open joints through shrinkage of sheathing — the crevices and 
other disfigurements usually met with where painting the new and repainting the 
old railway freight car equipment. In refutation to existing doubts in circulation, 
we will ask you to accept the evidence of the close observation made by us, from 
time to time, of some sprayed freight and other large surface work done by the 
P. & L. E. R. R. Co., in the beginning, convincing us that the results from a 
standpoint of durability will not suffer on the score of fact that the paint was not 
applied with a brush. 

"We will also advance the theory that we will be safe when we express 
the belief that the operation of a perfect atomized painting apparatus will not 




FIG. 325. — COMPRESSED AIR PAINTING MACHINE. 



injure the health of the operator, if the proper precautionary measures are 
taken. The safe-guard we would suggest against this possibility Is to use noth- 
ing but a perfect atomizing device, which should be worked to its full capacity 
with a sufficient generated air pressure to force the paint clear of nozzle on to 
work without dripping. The much-objected-to white spray, which is always per- 
ceptible during the spraying operation, on investigation will prove to be nothing 
worse than volumes of discharged surplus air, which becomes vaporous on forced 
release, from the fact of air being so much lighter than the heavier atoms of 
paint which is ejected with great force ahead on to the work, and not back, as it 
has been claimed, into the face of the operator. 



USE. 



849 



"This being the fact, we would judge there need be no danger apprehended 
a health sense, through the practical use of the pneumatic paint sprayer, where 
properly operated. Deeming the above summary a sufficient introductory for 
the paint spraying issue, we will now proceed to take up the question of com- 
parative cost of paint used, the utility of innovation, etc. 

"The folloAving is the estimated cost of the work done in the Pittsburg 
& Lake Erie Company's freight yard during the period in which the spraying 
apparatus was in operation. This is compared with the time and cost of work 
done with the brush the laborers are paid on the piece-work plan:" 





Piece Work. 


With Spray. 


1^ 




Hours. 


Cost. 


Hours. 


Cost. 




Box 


f 

% 


.60 
.30 
.50 
.10 
.30 
.10 


1-6 


.15 
.10 
.12 
.05 
.12 
.04 


75 


Coal 


66% 
76 


Coke 


Flat 


50 


Trucks, all cars 


60 


Roof only, box 







60 







The following is taken from a paper prepared by Mr. H. G. McMasters, 
master car painter, Illinois Central R. R. : 

"It takes from two to three hours, or we will be liberal and say two hours, 
to coat a 35-ft. box car with the brush. Now, we feel safe in making the asser- 
tion that a man who has never seen a spraying machine before can take one 
and coat a car in at least one hour at his first attempt, which even at that rate, 
is a saving of one hour per coat, and this will be increased as the workman be- 
comes accustomed to the machine. 

"So far with the sprayer we have been unable to show a very great saving 
in paint over the brush, but even if we do not make a saving in paint, and use the 
same amount we did with the brush, the saving in labor will pay us to use it, as 
the following figures (which we had occasion to take a few days ago) will show: 



PRIMING NEW 3S-FT. BOX CAR BY HAND. 

Labor 2 hours, at 20c $ 40 

Material, 14 lbs. paint, at Sc 70 

Total 

PRIMING NEW 35-FT. BOX CAR WITH SPRAYING MACHINE. 

Labor, 35 minutes, at 20c. per hour $ 12 

Material, 12 lbs., at 5c 60 

Total 

Total saving of 

Or 34.57 per cent. 



$1.10 



72 



38 



850 USE. 

"Saving of labor painting by spraying machine, 28c., or 70.83 per cent.- 

"Saving of material, painting by spraying machine, lOc, or 14.29 per cent. 

"Roof and trucks not included. 

"The above figures include placing staging around the car, making all air 
connections, filling and cleaning machine, replacing hose, etc., or the actual cost 
of priming one car. 

"The cost of second and third coating vary slightly, but are materially the 
same as above. We also find it profitable to use the sprayer on a number of 
things in the coach shop, but, as we said before, a little experimenting with one 
will show how really profitable it is." 



PRACTICAL PAINTING BY AIR. 

The illustrations on the following page show the Bryce Pneumatic Paint- 
ing Machine in operation painting the Pan House of the Arbuckle Bros. Sugar 
Refinery in Brooklyn. This building consists of ten (10) floors, each 200 by 87, 
and from 12 to 25 feet high, each floor having 60 brick columns, 500 feet in each, 
so that the average space to be painted on each floor is over 27,000 square feet or 
272,812 feet in all. The ceilings are of fire proof tile arched, walls and columns 
of brick. The entire building is being painted by The Bryce Machine under con- 
tract with John A. Chater, 132 Nassau Street, New York. King's cold water 
paint is used and the covering as applied by the machines is entirely opaque and 
white with one coat. The machines of which there are now two in operation are 
worked from a Clayton air compressor on the ground floor, air being taken up by 
an inch hose on the outside of the building and taken through the window on to 
any floor on which the machines are used. Fig. 326 shows one machine at 
work on one of the columns which has been left uncovered at the base. The 
ceilings on this floor are 12 feet to the arch and are sprayed from the floor without 
any scaffold by the use of a four-foot nozzle; other ceilings are over 14 feet. 
There is no return of material Irom the ceiling. 

Painting can be done in this way on floors or ceilings at the rate of 2,250 
feet an hour by actual test, though 10,000 feet is a good day's work for one man 
holding the nozzle. 

The tank shown on wheels holds 16 gallons of paint. On the left side of 
tank are shown the valves for injecting air and ejecting air and paint. These are 
in one casting which terminates in an inch pipe which is screwed into the top of 
the tank. Inside this pipe and connecting both with the air and paint valves of the 
casting is a ^^-inch pipe extending down to within i^ inches of bottom of tank. 
The single hose attached on the left of valve casting supplies air. Of the other 
two small hose on the right of valve casting one takes the paint and the other the 
air to the nozzle. The' valves represented by the small handles as shown in 
picture are all open. The air passing in at the left passes down the wide short 
pipe and pressing-on the top of the paint in the tank forces it up through the small 
pipe and out through upper valve and hose shown on the right of casting from 
whence it passes to the stem of the nozzle, and into an inner tube within the out- 



USE. 



851 



side tube of the nozzle passing out at a vent at the end of this tube where it is 
caught and sprayed by the air passing through the outer tube. 

The air in addition to performing this duty of forcing up the paint arso 
passes straight from the valve on the left to the lower valve on the right and 
thence through the hose to the stem of the nozzle where it passes through a valve 
into the outer tube of the nozzle catching the paint at the end of the inner tube 
and spraying it into a fine mist. When it is desired to stir up the paiiit' in the 
tank the valve handle- on the left is turned vertically up, when the air passes 
down the small tube in the tank stirring up the paint and mixing it thoroughly. 

The nozzle consists of two tubes one within the other with an air space 
between fitting into a stem or handle containing openings corresponding with 




FIG. 326. — PAINTING. ARBUCKLE SUGAR REFINERY BY THE BRYCE PNEUMATIC PAINT 

MACHINE. 

The column to the left partly painted. The upper part has been sprayed with 
white paint. The lower part still untouched. 



openings in both tubes which form the valves for regulating the flow of air and 
paint. These consist of openings in the outer and inner tubes so arranged that the 
flow of paint and of air can be regulated separately or together, or either or both 
shut off with one turn of the h'and. 

The machine illustrated has been developed with great care and ingenuity 
and is thoroughly well made and finished in every respect. It is the most highly 



I 



852 



USE. 



developed and, with one exception, the only machine in the market at this time, 
and is thoroughly protected by the earliest patents. 

These machines are more specially in demand for painting large surfaces 
and ceilings with kalsomine and cold water paints also for protective painting of 
large bridges and iron structures and ships with the different kinds of oil paints. 
They can also be used for first two coats on barns and houses. One man handling 




FIG. 327, 

Building 200x87, 10 floors, ceilings 12 feet, 60 columns on each floor. 

the nozzle will do the work of from eight to ten men with the brush, with often a 
complete saving of scaffolding. An additional saving is in the wear of brushes. 

At a late hour Mr. Chater reports that the U. S. Navy has purchased these 
machines for painting war ships in Dry Dock. 



THE APPRAISER'S STORES BLDG., PAINTED BY AIR. 

At the present time the iron works of the U. S. Appraiser's Stores, foot 
of Christopher street. New York Gity, is being pointed by compressed air. It 
is a ten-story building, covering an entire block. The painting is being done ,by 
the contractors, Post & McCord. Four painting machines, made by the Turner 
Machine Co. are being used. The whole outfit comprises one Clayton Com- 



USE. 



853 



pressor and four spraying machines. In operation it requires one man for each 
spray, and to facilitate he work three additional men are employed to carry paint, 
move travelers and be in attendance for whatever purpose may be required of 
them. One man v/ith a spraying machine can paint as much in 4 minutes as can 
be done by hand in 45 minutes. The paint used is ordinary red lead and oil. 

The average work of four men, each with a machine, has been 100,000 
square feet in 5 days, working 8 hours each day. Mr, John C. McCord is super- 
intendent of the work. The compressor is located on the fourth floor, and 40 




FIG. 328. — APPARATUS USED FOR PAINTING THE WORLD's FAIR BUILDINGS. 



lbs. pressure is carried. The machines work under 15 lbs. pressure, and do the 
work thoroughly. 

The incidents leading up to the painting of the Appraiser's stores are of in- 
terest in the way of the development of painting by air. The machine was perfected 
by Mr. C. Y. Turner, who was assistant decorator under Mr. F. D. Millett at the 
World's Fair in 1892. The work of painting the buildings was done by a rotary 
machine, and the material used was kalsomine. It was accomplished with great 
success. So rapidly was the work done that the inside of the great Manufac- 
turers' Building, which covered 31 acres of ground, was done in one month. The 



854 USE. 

largest amount of surface covered in an eight-hour day was 31,500 feet by one 
double spray outfit. Since that time a number of outfits have been furnished 
to manufacturers and others for painting and whitewashing, and the machine 
of to-day is much advanced from the stj^le used at the World's Fair. 

It was necessary to facilitate the painting of the structural iron of the 
Appraiser's stores. The machines mentioned were put in for a trial test by 
the Turner Machine Co. Red lead was used, and it was distributed in a most 
^satisfactory manner, and the machines were adopted. The machines in use by 
the various railroad shops are adaptations of the original Turner machine. 



PAINT FOR PNEUMATIC SPRAYING. 

Some inquiry having been made as to the requisite nature of paint to be 
successfully sprayed, we will say that any paste paint thinned down with oil to 
the proper consistency to be applied with a brush, can be handled with the spray, 
with sufficient force. It is not customary, however, to use a paint for this pur- 
pose (usually oxide of iron mineral) that weighs over ten pounds per gallon. 
If a semi-paste is used mix 3 parts Sipe's Japan oil with i part raw linseed oil 
thoroughly. Of this mixture take 7 lbs. and mix 3 lbs. of finely ground metallic 
paste paint, which makes a spraying paint that weighs 10 pounds per gallon. In 
an experiment of painting a gondola coal car recently we took the Patterson- 
Sargent Co.'s liquid mineral roof paint, which is a very heavy paint — too heavy 
for brush, without thinning, and weighs 17 to 18 pounds per gallon — and thinned 
it down with Sipe's Japan oil to about 11 pounds per gallon, and it worked suc- 
cessfully ; but a little greater air pressure and a pound lighter paint per gallon, 
would have produced better results. Sipe's Japan oil, being light-bodied and a 
good drier, is, with linseed, well adapted for this purpose. — R. R. Car Journal. 



JETS OF AIR. 



Air at 75 pounds gauge pressure will escape from a ^" hole in the receiver 
at the velocity of 548 feet per second, from a short pipe at the rate of 658 feet 
per second. The velocity of flow varies but slightly at different pressures, only 
as affected by the opening, which varies the co-efficient of contraction. Approxi- 
mate results may be obtained in practice by using the above named velocities for 
any pressure between 45 and 100 pounds. 

The rate of flow may be obtained from the size of the opening and the 
velocity given above. 

The heat of compression causes the greatest loss in the use of compressed 
air. This is being greatly reduced by the use of compound compressors. 

When the volume of air is heated 475 degrees above its initial temperature 
the volume, at the original pressure, will be doubled. 






USE. 855 

Air leaks in pipes are more expensive than steam leaks of the same size — 
)ut two and one-half times as great. 

The compression of air, at constant temperature, follows Mariotte's law, 
id is inversely as the volume, the pressure being calculated in absolute units — 
pounds more than gauge pressure. — National Engineer. 



PAINTING BUILDINGS BY COMPRESSED AIR. 

The following interesting description, by Mr. J. J. Hubbell, is taken from 
Michigan Engineers' Annual for 1897 : 

The buildings belong to the Buckley & Douglas Lumber Co., and included 
'main building 475 ft. long by 356 ft. wide. The structures covered about five 
acres, and there was fully 1,000 "squares," or 100,000 square ft, of surface to be 
covered with paint. Rough hemlock lumber was used in the sides of these build- 
ings, and the problem was to cover this siding with some preservative compound 
as cheaply as possible. After a full consideration of various washes, a mixture 
of good raw linseed oil and red oxide of iron was determined on. 

Bids were received from three local painters. One of these offered to fur- 
nish brushes and ladders and to apply the paint for. 35 cents per square ; another 
offered to do it for 28 cents if the company provided all material; and the third 
made a lump bid of $300 for providing labor alone. Each of these bids was reas- 
onable, but all of the painters deemed two coats necessary, and thought the season 
too far advanced to undertake the work at the time. In this emergency Mr. Hub- 
Isell determined to use corhpressed air for the work. 

He made his own sprayer at a cost of $10, and in addition provided 150 ft. 
of ^-inch hose, an air pump taken from a locomotive, and an air reservoir also 
taken from a locomotive. This latter had a capacity of 10 cu. ft., and was placed 
near the large building and connected to the air pump by J^-inch gas pipe. He 
says that he should have used ^-inch pipe, but the smaller pipe was on hand in 
quantities. Of the hose, 125 ft. were to connect the nozzle with the air reservoir, 
and 25 ft. to connect the nozzle with the paint bucket, the latter being elevated 
to about the level of the nozzle. 

The paint came in barrels of 50 gallons each, and to each head of these 
barrels was screwed an iron flange with a short journal attached. The barrel was 
hung on these journals and revolved by a crank so as to thoroughly mix the paint, 
which was then drawn off by a molasses gate set in the side of the barrel, two or 
three gallons at a time. In use the air pressure ranged from 40 to 50 lbs., and as 
the air passed through the nozzle it sprayed the paint in a fine cloud looking like a 
jet of red vapor. The discharge was controlled by a valve in the base of the 
nozzle, and the operator soon became expert and could paint 8 or 10 ft. above his 
head and the same distance below his feet. Two men were required, one to keep 
the paint bucket full, and the other to handle the brush. There was little waste 
of paint, though every crevice was filled, and the rough surface was covered better 
than it could have been done by hand. One gallon of paint would cover about 150 



856 



USE. 



sq. ft., and the two men would cover about 5,000 sq. ft. in one day. The windows 
were protected by a light movable canvas covered frame. 

The cost of the oil paint thus applied did not exceed 10 cents per 100 sq. ft., 
and the cost of painting the buildings, including all labor and a reasonable sum for 
the use of the air pump, pipe, reservoir and brush, was less than 15 cents per 
square of 100 sq. ft., or less than one-half the cost of painting by hand. 



PNEUMATIC PAINTING MACHINES. 

The interesting subject of "painting by compressed air" has the faculty ot 
keeping before the public as conspicuous as any other line of compressed air 
work. The August issue of the Railroad Car Journal prints the following re- 
garding it: 

"The ever progressive Louisville & Nashville Railroad Company is improv- 
ing the appearance of their property along the line of the P. & A. divi^on, between 
Pensacola and River Junction, by having all the section houses and a number of 
depots and water stations painted. The handsome new freight warehouse in 




FIG. 329. — PAINTING CAR TRUCKS. 

this city, now rapidly nearing completion, is also being painted, all this work 
being done under the supervision of Mr. C. D. Beyer, the foreman painter of 
the L. & N. Railroad shops in this city. There are about 85 buildings, the fresh, 
new paint on which will be very gratifying to the travelers along the line." 

At the M. C. B. Convention, held in June last, a discussion was opened on 
this subject by Mr. F. W. Brazier, Assistant Superintendent of Machinery of the 
Illinois Central Railroad. 

The topic assigned to me to speak on, "The Durability of Paint Applied to 
Freight Cars by Compressed Air," as compared with paint applied by the brush, 
is a question which our company has taken great interest in. We are at present 
repainting about 400 cars per week with compressed air. We are positive that we 
are getting better results, a saving in labor, and our cars are painted more thor- 
oughly than with a brush. We have cars that have been painted about two years, 
and in order to get reliable information for the benefit of this association, I sent 
out inquiry letters all over our system to have our foremen painters inspect any 



USE. 



857 



and all cars that they could find that were painted with air. I might mention 
the fact that we found most of the old school painters opposed to the air system 




FIG. 330. — PAINTING TOP OF CAR. 

when we inaugurated it. From one of our Southern States our painter reports 
as follows : 

Vicksburg, Miss. 
"In reply to your letter as to the durability of paint applied by compressed 
air, and the old method by brush, I would state that after making close observa- 
tion of several cars done by air and by brush, I find very little difference in them, 
and if any, it is in favor of cars done with air. 

(Signed) J. Glass, 

Foreman Painter." 




FIG. 331.— TOUCHING UP THE EAVES. 



Other letters follow which bring forth about the same results. Many of 
them acknowledge their skepticism in the beginning as to the chances of this 
method becoming a permanent institution in the painting of railroad equipment. 



858 



USE. 



The experience of nearly every one who has tested the capabilities and the dura- 
bility of the pneumatic painting machines has been of a highly satisfactory nature. 
In the trade, painting machines are being supplied by the Chicago Pneu- 
matic Tool Co., and their actual working is shown in the illustrations. They 
require only one hose — that for air — as the paint is sprayed directly from the 




FIG. 332. — PAINTING EDGES OF BOARDS. 

machine. Its convenience is evident and the testimony of practical painters will 
do much toward promoting its use wherever painting is done. 



THE MASON PAINTING MACHINE. 

It seems as if only a small number of people had heard of painting by 
compressed air, notwithstanding the many references made to it in this and other 
journals, and we constantly receive inquiries asking for information regarding 
this interesting process. A painting machine usually consists of a vessel for con- 
taining oil or cold water paint and a means for forcing it through hose to a spray- 
ing nozzle by which it is applied. At the point where it is ejected it is met by a 
small stream of air which atomizes the paint and thus puts it under control so that 
it may be sprayed on the surface to be painted. That is the operation, but much 
depends upon the construction of the machine itself, for if not properly con- 
structed it fails in the most important features. In some cases it has been found 
impossible to operate home made machines or machines made on wrong principles. 

A very successful machine for this purpose is the "Mason," manufactured 
by the Alden Speare's Son Co., 74 John street. New York. 

The Mason Painting Machine consists of a hand air compressor, with a 
steel tank for storage of liquid paint or whitewash and the air. It has no rubber 
valves to be destroyed by any chemicals which may exist in material used. No 
material can get at the valves or any part of the mechanism (which is extremely 



|pt^^ I^IF ii.,-KfTr 



USE. 



859 



simple in its construction), to put it out of order. By an ingenious device the 
paint is automatically kept agitated and settling prevented. Only forty pounds 
pressure required to operate it, and" the tank is guaranteed to stand a pressure of 
two hundred pounds. It can be operated either by hand or power. It will apply 
with equal economy and facility oil paint, cold water paint or whitewash. It is 




FIG. 333. — THE MASON PAINT MACHINE. 



complete in itself, but can be arranged to be used in connection with a supply of 
air when such is at hand. 

The cut herewith shows the construction of this machine in complete work- 
ing order. The Spearcs Company are manufacturers of cold water paint, and the 
demand for an apparatus for properly applying their product led them to adopt 
this one and manufacture it to accommodate their patrons. A full knowledge of 



86o USE. 

{.he reqii 
the user. 



Lhe requirements qualify them in offering it with assurances of satisfaction to 



PNEUMATIC DESPATCH. 



On Thursday, October 7th, 1897, the Tubular Dispatch Co, gave a public 
demonstration of the Batcheller Pneumatic Dispatch Apparatus at the New York 
Post Office. Few appliances meet with a more auspicious reception or launch 
more genuinely into national importance than this one did. The company's line is 
laid from the Post Office to the Produce Exchange. Among those present at the 
opening were Hon. Chauncey M. Depew, Second Assistant Postmaster-General 
Shallenberger, ex-Postmaster-General Tyner, John E. Milholland and many 
others. At 12 o'clock Mr. Depew pulled the lever that sets the sending apparatus 
loaded with the carrier in place before the tube. Air pressure was automatically 
applied, and the carrier was projected on its journey. It went to the Exchange 
Building, which is 4000 feet distant, and was returned. The trip took 4.35 min- 
utes. The carrier is 24 inches long and 7 inches diameter. 

It contained a variety of goods. The operation was repeated several' times, 
each time carrying sundry articles. The table in front of Mr. Depew looked like 
that of a magician, whose exhibition brings forth beautiful and dazzling objects. 
Among the things carried were a bible, a copy of the Constitution of the United 
States, a bunch of violets, an American flag, fruit, clothing, shoes, bric-a-brac, a 
bottle of. wine, a live cat, etc., etc. 

The air pressure necessary was 6 pounds. There is a receiving apparatus 
at the end of the tube that checks the speed of the carrier by means of an air 
cushion. Then it is opened automatically and allows the carrier to emerge. It 
comes out upon a receiving table and strikes against buffers made of felt and 
other flexible material. 

The demonstration was a success, and the hard work of the projectors of 
this system has terminated by a great triumph. 

The system will probably be extended throughout New York City and 
Brooklyn. The work is now going on in Boston and Philadelphia and other 
large cities. 



PNEUMATIC DESPATCH. 



We are glad to note the successful introduction and use of the pneumatic 
system of conveying mails in, cities. The Batcheller system is now in continuous 
operation in New York City, special carriers being provided for conveying the 
mails through a tube 8" in diameter. In this system the carriers slide through 
the tube, a condition which is probably limited to tubes of 8" to 10" in diameter. 
It would seem that tubes of small diameter cannot be as serviceable or as econom- 
ical in post offices or package delivery work owing to the labor required in trans- 
ferring the packages. Tubes large enough to carry mail bags or common express 
packages would have many advantages and it is likely that a system of this 



USE. 86i 

kind will be brought forward. The Bostedo Package and Cash Carrier Company, 
of Chicago, has designed such a system for transmission of large packages over 
long distances. It is proposed to use tubes from i8 to 30 inches in diameter, a size 
large enough to carry the largest mail bags and it is also claimed that the principles 
involved may be applied advantageously to tubes of any size down to six inches 
in diameter. 

In designing the system the first consideration was to do away with the 
friction of sliding carriers through the tubes, as is the practice with smaller tubes. 
In order to do this a carrier was designed mounted upon large wheels, the diame ■ 
ter of each wheel to be at least one-half the diameter of the tube, one wheel in 
front of the receptacle and the other behind it; the wheels to run either in a 
groove cast in the tube, or on a rail laid in the tube. The receptable, which is a 
cylindrical box nearly filling the tube, is prevented from scraping the wall of the 
tube by four friction rollers, two in front and two behind, set at an angle of about 
45 degrees from the vertical axis of the tube. With this construction it is obvious 
that the tendency of the carrier while moving in a straight line will be to assume 
a vertical position, the function of the friction rollers coming into play only in 
turning curves and in the case of the carrier being overloaded on one side. 

By the use of ordinary cast iron pipe, another advantage of this system over 
the systems which use sliding carriers, is that it is unnecessary to bore out the 
tubes. The tubes will be sr6</oth enough as cast, excepting abnormal roughnesses, 
which of course should be ground or chipped out. Another advantage is that the 
packing used will not be a hard problem, as it is not the intention to have the 
packing actually touch the wall of the tube (except in the terminals). It is suffi- 
cient for practical purposes if the packing is within say one-quarter to one-half 
inch of the wall of the tube, as the proportional area of the clearing space to the 
cross-section area of the carrier is insignificant. Attention is called to the fact, 
that it is no more possible for a sliding carrier to actually fill the tube than it is 
here, the difference being that in this case a uniform annular clearance is left all 
around the carrier, while in the case of a sliding carrier there is actual contact 
at the bottom of the tube, with the maximum clearance at the top. 

Leaving out for the present any description of the switches, the use of 
which will probably be in the remote future, if at all, we will describe the ordinary 
system, consisting of a pair of tubes with a pawer station at one end. 

The system can be operated upon either the exhaust or the pressure princi- 
ple. For the present we will confine our description to the pressure type. In this 
system the air makes a complete circuit. It is taken by the blowing engine from 
the incoming tube, and discharged into the outgoing tube, the two being connected 
at the outer end. The delivering apparatus is the same at both ends, and its 
operation is as follows : The end of the tube is normally closed by a valve, and at 
the proper distance back from the end to effect the desired result, is another valve, 
which is normally open. Still further back from the end of the tube, the air 
current is diverted from the tube and directed either into the return tube or into 
the blowing engine, as the case may be. The carrier, arriving at its destination 
first passes the opening where the air is diverted from the tube. Immediately 
after passing this opening, it begins to compress the air ahead of it. The parts of 



862 USE. 

the terminal are so proportioned that the carrier is permitted to pass the normally 
open valve before sufficient pressure has accumulated ahead of the carrier to close 
said valve. However, immediately after the carrier passes the normally open 
valve, the compressed air ahead of the carrier closes the valve behind it. After 
this valve is closed, the carrier, which is still moving forward, begins to rarefy the 
air behind it; that is, the air which is between it and the valve which has just 
closed. The difference in pressure between the compressed air ahead of the 
carrier and the rarefied air behind it, tends to bring the carrier to a stop, while 
at the same time the difference in pressure in a supply pipe taken from the main 
tube and the rarefied air behind the carrier, is utilized to open the end valve, which 
permits the delivery of the carrier out of the tube and on a track. The parts are 
so proportioned that most of the momentum of the car is absorbed in operating 
the two valves. Enough momentum is left, however, to cause the carrier to roll a 
convenient distance out on the track, where it may be unloaded and loaded. The 
track then leads around towards the mouth of the return tube. 

The despatching apparatus is operated by hand, by means of a controlling 
box analogous to that on a trolley car. The movement of the operator in despatch- 
ing carriers is even more simple, and is quite similar to that of the trolley car 
operator. The track leading into the mouth of the return tube is slightly inclined, 
so that when the carrier is released by the operator, it rolls into the mouth of the 
return tube. The return tube has two valves, one being at the mouth of the tube 
and the other at a convenient distance from the mouth. The air supply pipe to 
the main tube also has a valve which when closed, diverts the air from its normal 
course, around behind the carrier which has been allowed to roll into the mouth 
of the tube. We thus have three gates or valves in the despatching apparatus— 
the one at the mouth of the tube and the one which diverts the main air current 
being normally open, and the other valve, which is located some little distance 
from the mouth of the tube, being normally closed. It is obvious that what is 
desired after the carrier has rolled into the mouth of the tube is to first close the 
gate behind it, then open the gate in front of it, and then turn the main air cur- 
rent in behind the carrier in order to propel it into the main tube, where it will be 
caught by the constant main current ; and then to return the three gates to their 
normal positions. All of this is effected by operating these three gates with 
pistons, the opposite ends of the cylinders for the three pistons all being connected 
with the controlling box, and the controlling box also being connected with the 
main pipe. The controlling box is so arranged that the operator may at will 
reverse any of the gates, this being effected by the difference in pressure of the 
atmosphere and the air in the supply pipe from the main; the controlling box 
bemg so constructed that the operator, by moving a lever, can put one end of the 
cyhnder which he desires to operate, in communication with the pressure main, 
and the other end at the same time in communication with the atmosphere. 

There are many details of design which it is our purpose to illustrate and 
describe in a subsequent issue. 



USE. 



863 



PNEUMATIC TUBES. 

The carrying of mail or parcels of any kind through pneumatic tubes is a 
very old idea. The most common illustrations are the "Petit Bleu" in Paris, a 
practical system which has been in operation for many years. By this system 
one may write a telegram or a letter and have it forwarded in a sealed envelope 
to its destination by passing it through a pneumatic dispatch tube. The purpose 
of this is to facilitate dispatch, and to a certain extent it takes the place of the 
telegraph or telephone service. These things are largely matters of custom; 
people in Paris are accustomed to this way of doing things, while in America we 
resort to the telephone, or we send a telegram or a special delivery letter. An- 
other common illustration of the pneumatic tube is seen in department stores, 
where packages are transmitted to different parts of the building. These are 
simple cases, involving few if any difficulties, because the work is done on a 
small scale. During recent years important advances have been made in the 



PfJcuilATiC Tl/ISC ^C/jlHlC^ 




ft<0 ^lew or Ti/ec Jir^ Cf 



/yy: 



OlJ tcj twi tfl^ Carritr trt&t Uij,t/% C ^^,<.{ frm.'tt 
in tf/t gnoiA * If tit, ySie^ a/ftt nt/ot^t '» ircty 4<.r<*^* 






FIG. 334. 



direction of perfecting mechanism by which carriers of large diameters are trans- 
ported through tubes, and the success and utility of the systems now in use in 
large cities for doing this are niatters that are no longer questioned. 

Those who are interested in the investigations being carried on by Congress 
in pneumatic dispatch systems for the transportation of mails in large cities will 
perhaps be surprised to learn that in addition to the two systems that have re- 
ceived so much publicity, the Batcheller system and the Bostedo system, another 
thoroughly equipped system, 2,400 feet in length, at Burlington, N. J., has been 
drawn to the attention of the Congressional Committee. 

Mr. John Mclntyre has recently made some interesting investigations of this 
new system, and through him we learn that as long ago as 1896 this system, which 
is owned by The United States Pneumatic Dispatch Company, was thoroughly 
investigated by a committee formed of men in high position in the government 
service, who were appointed by Postmaster-General Wm. L. Wilson. That com- 
mittee recommended that the system be built between Brooklyn and New York 



864 USE. 

over the Brooklyn Bridge. The Postmaster of New York, Charles Dayton, and 
the Postmaster of Brooklyn, W. T. Sullivan, heartily supported the report, which 
Postmaster-General Wilson approved. However, for some reason never ex- 
plained, another system was built. 

The United States Pneumatic Dispatch Company has not advertised its sys- 
tem, nor has it frequented the Capitol building at Washington. This company 
claims for its system many advantages over the Batcheller system, which is now 
carrying the mails, or rather, a portion of the mails, in Philadelphia, New York 
and Boston, and the Bostedo system, which is now being built in Boston for the 
light package express business. The Batcheller system carries the mail loose, 
necessitating it being handled by tube company employees at each end of the 
system — this would be true of the Bostedo system — whereas the carriers used 
in the Burlington system accommodate at least three or four of the regulation 
locked mail pouches filled with mail of any class. For mechanical reasons, and, 
without certain important changes, it is doubtful if the other systems named could 
be enlarged to accomplish this important point in the transportation of mails. 

The system at Burlington is 2,400 feet long, as has been stated, the pipe being 
unfinished 24 inches inside diameter, cast with grooves at top and bottom, in 
which the wheels sustaining the weight of the carrier run. At the terminal sta- 
tions the carriers run out on rails, and therefore do not have to be lifted or car- 
ried, as is the case with the Batcheller and Bostedo systems. The carrier is sent 
through the tube at a speed of 33 miles an hour, with, a pressure of 7 ounces. 
This speed was increased to over 50 miles an hour for the last examining com- 
mittee. A Connersville blower is used to operate the line. There is a loop of 
16 feet radius and several automatic Y's and switches into which the carriers can 
be guided, thus showing the practicability of diverting the carrier into any sub- 
post offices or side stations that might be established. 

It is not necessary to machine or to bore out tubes used by the United States 
Pneumatic Dispatch Company. The cost of boring is greater than the cost of the 
tube itself. The statement made to the Second Assistant Postmaster-General by 
the Pneumatic Tube Investigating Committee, under date of December 4th, 1900, 
shows that a bored tube six inches in internal diameter would cost $1.12^ a foot, 
and such a tube eight inches in internal diameter would cost $1.50 a foot. The 
tube used by the United States Pneumatic Dispatch Company, however, would 
cost for one six inches in internal diameter less than forty-five (45) cents a foot, 
or one eight inches in internal diameter less than sixty-five (65) cents a foot. 
At the cost given above for a six-inch bored tube ($1.12^ a foot), one of the 
tubes of the United States Pneumatic Dispatch Company twelve inches in internal 
diameter could be furnished, and the latter would have a capacity four times as 
great as the six-inch bored tube, or at the cost given above for an eight-inch 
bored tube ($1.50 a foot), one of the tubes of the United States Pneumatic Dis- 
patch Company fourteen inches in internal diameter could be furnished having 
three times the capacity of the eight-inch bored tube. A twenty-four inch tube 
such as is at the exhibition plant in Burlington would cost less than three dollars 
($3.00) a foot. 

The cost of operating the United States Pneumatic Dispatch Company's sys- 
tem should be materially less than the bored tube now in use. On the latter it 



USE. 



S65 



IS necessary to maintain a pressure of from three to seven pounds to tlie square 
inch, whereas the United States Pneumatic Dispatch Company's carriers can be 
operated with from five to seven ounces of pressure. It is claimed that with the 
United States Pneumatic Dispatch Company's system it is possible to transport 
all the mail of all classes, thus eliminating the cost of wagon service entirely, and 
to carry all the mail at less cost than is possible with wagons, and that by this sys- 
tem the whole body of the mail may have as rapid dispatch as a small portion, or 
what might be called supplemental mail. 

By this system the mail can be carried in regular pouches, sealed at the dis- 




FiG. 335. 



patching office by regular postal officials, to be delivered in like sealed condition 
to postal officials at the receiving points. 

This is an important point in that the mail, when once placed in the bags, 
remains intact, and is not subject to losses due to breaking of bulk, and is, there- 
fore, less liable to damage either through accident or design. The use of air at 
low pressure is always an advantage, it being a well-known fact that the cost of 
compressing air increases directly as the pressure, the volume remaining the 
same. 

The simplicity of the air compressing apparatus is greater for lower than 
for higher pressures, and its efficiency should also be greater. If it is true, as 
claimed, that this new system of pneumatic dispatch may use air supplied by a 
blower, we might reasonably expect economy, and in view of the large diameter 
of the pipe, friction losses are probably reduced to a minimum. 



866 USE. 

PNEUMATIC DISPATCH TUBES. 

It is announced that Philadelphia is to be the first city in the United States 
to be generally equipped and gridironed with a system of pneumatic dispatch 
tubes, for mail matter, telegrams and light packages. The pioneer American 
pneumatic tube for postal service was put in operation in Philadelphia a few 
years ago, and is a great practical success. It is about a half mile in length, 
extending from the Philadelphia Stock Exchange to the Post Office. The tube is 
65^ inches in diameter and is capable of carrying 48,000 letters per hour. 

There are some private or semi-private installations of pneumatic dispatch 
tubes in use in this country by the telegraph offices and the newspapers, but gen- 
erally we are far behind European cities in our appreciation and use of this means 
of transmission. The system has been in efficient operation for years in London, 
Paris, Berlin and Vienna. The systems employed in these different cities are quite 
different from each other in the details of construction and operation. For in- 
stance, London uses what is known as the radial system, and Paris uses the cir- 
cuit system. In London, both outgoing and returning tubes are laid radiating 
from a central station ; while in Paris a single pipe from the central station makes 
a circuit of outlying stations and returns to the starting point. The circuit sys- 
tem is used in Vienna, but in Berlin the circuit has been changed to the radiating 
system. 

The tubes employed in all the European installations are of comparatively 
small diameter. London operates 42 stations and 34 miles of tubes, carrying, it is 
estimated, 57,000 messages per day. Paris, with less than 20 stations, transmits 
nearly as many messages as London. Berlin has 38 stations and 28 miles of double 
tubing. 

In the details, both of construction and operation, there is quite a diversity 
of practice. In London the individual carriers are operated upon by the pro- 
pelling force ; in Paris, pistons take long trains of carriers after them. In some 
cases a vacuum in front of the carriers is created, and in others compressed air 
operates behind them, or sometimes a combination of both methods is employed. 

The sticking of carriers in the tubes is a serious occurrence, but means have 
been devised for meeting such a contingency. The fine system of sewers in Paris 
leaves all the tubes in that city easily accessible. When a pipe is obstructed a 
diaphragm is attached to the end of it, and a pistol shot is fired into the tube 
through an opening just below where the diaphragm is placed. The sound acting 
on the diaphragm, closes an electric circuit and makes a mark on a chronograph. 
The sound wave traveling through the tube, meets the obstruction and is reflected, 
and upon its return makes another mark on the chronograph. The interval of 
time indicated by the chronograph gives a ready means of determining the dis- 
tance of the obstruction from the end. 

We should be able now in this country to make a fine exhibit and a great 
success of pneumatic transmission, as we have the benefit of forty years of Euro- 
pean experience. — American Machinist. 



USE. 867 

THE PNEUMATIC MAIL TUBE SYSTEM * 

The system by which matter is transported through closed tubes by means 
of a current of air therein, is not a new idea by any means, though its successful 
application for commercial purposes is of recent date. 

The earliest ideas of pneumatic transportation are found in the records of 
the Royal Society of London. Here we learn that Denis Papin sent to the So- 
ciety in the seventeenth century an article on the "Double Pneumatic Pump." 
He exhausted the air in a long metal tube, causing a piston to move through it, 
which drew after it a carriage attached by means of a cord. 

It was not, however, until 1853 that the first successful pneumatic tube 
system was built in London. A one and one-half inch pipe was laid between 
Founder's Court and the Stock Exchange. Its length was 650 feet, and the 
carrier was propelled through it by means of a vacuum created by an exhausting 
engine at one end of the line. The roughness of the interior of the iron pipes 
caused much trouble, and in 1858, when the system was* extended, two and one- 
half inch tubes made of lead were used, the carriers being made of gutta percha 
with an outer lining of felt. 

From this small beginning the London system has grown rapidly and now 
comprises forty-two stations, connected by thirty-four miles of tubes. The latter 
are made of cast iron with a lining of lead, and vary in diameter from two and 
three-sixteenths to three inches. The lines are laid out radially, and the air 
exhausted at one end and compressed at the other. This system has been 
adopted in Liverpool, Birmingham, Manchester, Dublin and Glasgow. Experi- 
ments were also made in London with an underground pneumatic railroad. In 
1863 one was built eighteen hundred feet in length and two feet eight inches 
square. A second was constructed in 1872 from the Post-office to Euston sta- 
tion, a distance of two and three-fourths miles. This one was somewhat larger 
than the first, being four and one-half feet wide by four feet high. These tun- 
nels were operated by means of fans, which forced air into one end and ex- 
hausted it from the other. They were never a success, however, and were soon 
abandoned. 

In 1865 a system of pneumatic tubes for the transmission of telegraph 
messages was built in Berlin. Wrought iron pipes, two and one-half inches in 
diameter, were laid in pairs, one being used for sending and the other for re- 
ceiving messages. The tubes were connected at one end by a loop and a steady 
current of air kept up by means of a compressor at one end and an exhauster 
at the other. The system now in use there, however, is somewhat different, the 
power being supplied by large storage tanks containing compressed air. There 
are altogether thirty miles of pipe and thirty-eight stations in the city. 

The Paris pneumatic system has been in operation for many years and 
most of the branch post and telegraph offices are connected with each other by it. 
A novel method of compressing the air is used, for instead of employing a steam 
engine, it is compressed in tanks by displacement with water. The diameter of 
the tubes now used in Paris is 2.55 inches. The carriers are sent out in trains 
of from six to ten, and are propelled by a leather covered piston at the rear 
which fits tightly in the pipe. 

♦Yale Scientific Monthly. 



868 USE. 

In 1867, at the American Institute Fair held in New York, the late Alfred 
Beach exhibited a pneumatic tube railroad. A car, holding ten people, ran on a 
track laid down within a circular wooden cylinder which was about 100 feet long 
and six feet in diameter. A current of air was supplied by a large fan, running 
at the rate of two hundred revolutions per minute. He later built a tunnel under 
Broadway, near Warren street, extending a distance of two hundred feet. The 
car was driven by a large rotary blower in an adjoining building, and could be 
made to go in opposite directions by simply reversing the valves of the blower. 
Mr. Beach also designed a system of pneumatic tubes to convey mail from the 
street boxes to the postoffice. The letters were to be delivered into cars from 
revolving hoppers, which were made to turn by pins on the car hitting the vanes, 
the carriage being propelled by a current of air. He also, a few years later, built 
a line of over one thousand feet in length with a very smooth interior. This 
pipe led to a large receiving box connected with an exhausting engine. A letter 
dropped into the pipe at any point was carried along by the current to the box, 
where it fell to the bottom, from which it could be easily removed. 

For many years the pneumatic tube has been a common means for the 
transmission of cash, etc., in large stores. The Western Union Telegraph Com- 
pany, several years ago, connected a few of its offices by a pneumatic system, 
but the first real attempt to introduce it on a large scale into this country was 
made in 1893 in Philadelphia. A six-inch main was laid to connect the main post 
office with the Chestnut street branch, a distance of nearly a mile. On account of the 
large size of the pipes compared to those used in the European system, the capa- 
city of this plant was much greater. The area of the tubes was increased many 
times, and of course the carriers were correspondingly larger. The speed of the 
Philadelphia system was moreover doubled and had improved appliances for 
receiving and transmitting. This plant was opened in 1893 and has been operated 
successfully ever since. 

When in 1897 the tubular Dispatch Company of New York was authorized 
to construct a pneumatic tube system for the transmission of mail between the 
General Postoffice and some of the branch stations, all the different plants then 
in use were inspected. After careful investigation, the company decided to copy 
after the Philadelphia line, which had proven so successful, and plans were 
accordingly drawn for a system running from the postoffice to the Grand Central 
Station, the Produce Exchange, and to Brooklyn, over the Bridge. The first 
line to be put into operation was the one running to the Produce Exchange, 
which was opened in the fall of 1894. The others have since been completed, or 
will be at an early date. 

The company determined to make the tubes of larger capacity than those 
used in Philadelphia, and to maintain a working speed of thirty miles an hour 
under a headway of twelve seconds. The line to the Produce Exchange is nearly 
four thousand feet long and consists of two tubes, side by side, eight inches in 
diameter, and about five feet below the surface. One is used for outgoing and 
the other for incoming mail, they being connected at the sub-station by a loop. 
A powerful compressor forces the air into the outgoing tube at a pressure of 
seven pounds to the square inch. On account of its elasticity, it flows through 
the pipe with an increasing velocity, but by the time it reaches the sub-station 



1 



USE. 869 

the pressure has fallen just one-half. From here the current returns by the 
second or return tube, and as it enters the receiving tank its pressure is equal 
to chat of the atmosphere. This tank is joined to the suction pipe of the com- 
pressor, and as the two lines are connected by a loop at the other end, there is a 
continual circulation of air throughout. The pipes are of cast iron with a very 
smooth interior finish. All bends are of at least eight feet radius and made of 
seamless brass with a diameter of not less than eight and three-fourths inches on 
the inside. 

The carriers are made of thin steel plates rolled into a cylinder, riveted 
and soldered. They have two bearing rings of packing, one at each end, which 
fit the tube and prevent any air getting by, causing it to move with the same 
velocity as the current. The shell proper is about two feet long and seven inches 
in diameter. The front end is concave and has a filling of felt which protects it 
from any shock it may receive. The rings form the sliding contact and keep the 
shell proper from touching. The carriers are closed by a hinged door at the 
rear, which is so arranged that it cannot open while in the tube. 

The current is continuous from the starting of the compressors in the 
morning until they stop at night, so it was necessary to have some means by 
which the carriers could be inserted and removed from the line without inter- 
fering with the flow of air. This is done by means of a transmitter and 
receiver, one at each station. The former consists of a piece of eight-inch pipe, 
long enough to enclose the carrier. It is hung on a shaft, overhead, so that it 
can be swung out from the main line to receive the carrier and then moved back 
into position where the current forces the latter into the main tube. The ends 
are smoothed off square so that no air can escape at the joints. When this sec- 
tion is swung out of line two projecting plates move across the ends of the open- 
ing and shut off the air, the current meanwhile going around by means of a 
connection. When the transmitter is not in use the movable section is drawn 
over to the loading tray and the air goes through the U shaped by-pass. When 
a carrier is to be sent it is placed in the tray and pushed into the transmitter, 
then, by pulling a lever, the latter is swung into position and the carrier is forced 
out. An automatic time-lock prevents them being sent with less than twelve 
seconds headway, thus ensuring a proper distance between them in the tube. 
When the carriers arrive at the sub-station the pressure of the air is three and 
one-half pounds to the square inch, so the tube cannot be opened to remove them. 
They also have a velocity of about thirty miles an hour, and some means had to 
be provided for gradually checking their speed. These two things are accom- 
plished by means of a closed receiver which consists of an eight-inch cylinder 
four feet in length. In its normal position it forms a continuation of the tube by 
which the carrier arrives, and on entering the receiver, it compresses the air in 
front and is stopped without any shock. There are a number of openings in the 
pipe just in front of the receiver connected with the other or returning line by 
which the current continues back to the main station. The compressed air in the 
receiver opens a small valve and thus keeps the carrier from being thrown back 
into the main tube. The receiver is automatically discharged in three or four 
seconds by a piston, which tilts it to an angle of forty degrees. The carrier 
slides out onto an inclined platform which is kept in position by a counter 



870 USE. 

weight. The weight of the carrier, however, overbalances this and causes it to 
drop to a horizontal position, and the carrier is thrown out onto a table in front 
of the operator. This piston is worked by compressed air supplied from the re- 
ceiver. Above the front end of the receiving chamber is a plate, arranged so 
that it comes down and closes the end of the main tube when the receiver is 
tilted to be discharged. 

The transmitters at both ends of the line are the same, but the receiver at 
the main office is very different from the one at the sub-station, which is described 
above. At this end it consists of a section of the end of the tube closed at the 
rear by a gate. The air, now expanded to the same pressure as the atmosphere, 
passes from the tube through openings, four feet in front of the receiver gate, 
down to the tank in the basement. The momentum of the carrier is checked 
in compressing the air in the chamber after it has passed these openings. Part 
of this compressed air operates a piston which opens the gate mentioned above, 
Ihen the small pressure of air forces the carrier out onto the receiving table. 
If there is not sufficient pressure to expell it, the openings can be partly closed by 
means of a valve. As it passes out, it hits a small finger which causes the gate 
to be closed. 

These, in brief, are the main features of the pneumatic tube system. Im- 
provements are continually being made in the line of quicker handling and 
greater capacity, and now that it has been proven a success there is every pros- 
pect that it will come into general use in all large cities for transmitting mxail to 
the various sub-stations. .Plans are now being considered by the postoffice de- 
partment to further extend the present lines in New York, as well as in other 

cities. J. FOSTER SYMES. 



MAIL TUBES IN TIMES OF A BLIZZARD. 



THEY SAVED THE LOCAL SERVICE, BEING INDEPENDENT OF SNOWDRIFTS. 

One of the worst snow storms that ever visited the Eastern States was ex- 
perienced during Feb'y 12th, 13th and 14th, 1898. Steam, electric and ordinary 
traffic were suspended, and the New York Sun makes the folllowing report on the 
Compressed Air system of transmitting mail : 

"The snow did not cause half the delay in the local mail service that many 
smaller storms have caused, and Assistant Postmaser Morgan declared yesterday 
that it was the pneumatic mail tubes that saved the service. The tubes run from 
the main Post Office to the Produce Exchange, from the main office to the Grand 
Central Palace and from the main office to the General Post Office in Brooklyn. 
The Forty-second street line has a number of branch lines that connect with 
branch stations between the General Post Office and the Grand Central Palace. 
The tubes being under ground, of course, imusual conditions on the surface do not 
affect them, and since the changes that have been made in their management and 
operation they have done remarkably good service. 

It has always been New York's experience in a storm that tied up the street 
traffic to have the mail service tied up, too. The big wagons could not get around 
ill the storm to collect the mail from the stations and things simply had to wait 



USE. 871 

until the conditions were improved. This has caused untold inconvenience and 
trouble and in some cases loss to business people. The Assistant Postmaster said 
yesterday when he was asked about the conditions of the city service : 

"I'here has been little or no delay in our city delivery, and this has been 
largely due to the effectiveness of the pneumatic tube service. The mail wagon 
service was seriously hampered and for long distances was rendered practically 
useless by the snow. But the tubes did their work on time and most of the down- 
town and uptown mail went through them. They were especially serviceable in 
delivering the mails to what is called the Wall street section of the city. Brook- 
lyn and the upper section of Manhattan borough also profited from the fact that 
the snow could not block the tubes. They certainly have proved to be an espe- 
cially valuable adjunct to the postal service in weather like this, and have enabled 
us to deliver large quantities of mail, which, under the old mail wagon system, 
would have stalled in the main office here." 

The Assistant Postmaster explained that the tubes carried nearly all the 
first-class letter mail between the stations they connected, and that in the delivery 
of special delivery letters, particularly, there was scarcely any noticeable delay. 
It took the messengers who carried these letters after they reached the offices a 
little longer to get around, of course, but that was all. Some of the Post Office 
folks and some of the employees of the Despatch Company, which owns the tubes, 
declared that all during the storm the Post Office beat the telegraph companies 
when they came into competition, and that letters when they bore the 10 cent 
special delivery stamps, reached their destination ahead of telegraph messages 
sent at the same time. 

The delay in the mail service was confined entirely to the out-of-town 
service and the service in that part of the city where the tubes do not reach. But 
the service in those parts of the city was better than usual, too, for the effective 
work of the tubes made it possible for the postal authorities to withdraw some 
of the wagons used on the tube route and send them to the unsupplied districts to 
help out." 



RECENT PROGRESS IN THE DEVELOPMENT OF PNEUMATIC 
DISPATCH TUBES.* 

As you all know, pneumatic dispatch tubes are not an invention of recent 
date; that is to say, their commercial application began forty-five years ago. 
Every one is more or less familiar with them, as they are used in large retail 
stores for the transmission of cash from the various counters to the cashier's 
desk. Many large office buildings are equipped with them for dispatching mes- 
sages from one office to another. The Western Union Telegraph Company has 
used them since 1876 in New York City to transmit their telegrams from one 
office to another, it being found more expeditious than the telegraph. 

The United States usually takes the lead in the application of mechanical 
devices, but in the uses of pneumatic dispatch tubes, we are behind our European 
neighbors. London, Paris, Berlin and Vienna for years have had their pneumatic 
* Journal Franklin Institute. 



872 



USE. 



tube systems for transmitting telegrams between the central and branch post 
offices. The service is not confined to the large cities, for Liverpool, Brussels and 
other smaller cities are now equipped with this modern method of transportation. 

There is much misconception of the size, capacity, length and use of the 
tube systems of Europe, for which the daily press is principally responsible. I 
have seen it stated that Paris and Berlin are connected by pneumatic tubes. It 
goes without saying that such a statement is untrue. Many people believe that 
mail is sent through the tubes, but that is also untrue, for the tubes are not large 
enough for that purpose. They are used only for the transportation of telegrams 
and messages. The largest tubes in London are only 3 ins. in diameter, while 
those of Paris and Berlin are about 2%. ins. Fig. 342 shows the Berlin and 
London carriers. 

The first tube was laid in London in 1853 by the Electric International Tele- 
graph Company, under the direction of Mr. Josiah Latimer Clark. It was V/z ins. 




FIG. 336. — SENDING APPARATUS AND OPEN RECEIVER, PRODUCE EXCHANGE LINE, MAIN 
POST OFFICE, NEW YORK CITY. 



in diameter, and extended from Founder's Court to the Stock Exchange, a dis- 
tance of 220 yards. Year by year the system has been extended, until now the 
entire business section of the city is covered by the network of tubes radiating 
from the General Post Office and terminating in the numerous sub-Post Offices. 
(In England the telegraph is controlled by the Government, and the telegraph 
offices are in the post offices.) The tubes are of lead, encased in cast iron and 
laid in pairs for dispatching in opposite directions. Berlin has a similar system 
to that of London, but in Paris the tubes are laid in circuits with several stations 
on a circuit. The carriers are forwarded in trains from one station to another 
around the circuit. 

It is not the purpose of this paper to describe these European systems in 
detail, but I refer to them to give some idea of the state of the art up to 1893. 

Admitting that the European cities have gotten the start of us in point of 
time, we are bound not to be beaten in the end. While they continue to operate 



USE. 



873 



their small 2 and 3-inch tubes for telegrams only, we begin by building 6-inch, 
and use them to transport mail in large quantities, and the beginning was made 
in the city of Philadelphia five years ago, when the first line was opened by the 
Hon. John Wanamaker, then Postmaster-General. 

It may seem to many of you like a simple step, from 3-inch to 6-inch tubes, 
but I will say from experience that the small tubes were no guide or help to us 
in building larger ones. The methods of operation and apparatus used with the 
small tubes could not be applied to the larger. The principal reason for this lies 
in the greatly increased weight of the cartridge, or, as we term it, carrier, that is 
dispatched through the tube. The weight causes friction against the walls of the 
tube and is a storehouse for energy that must be taken care of when the carrier 
is brought to rest. A heavy carrier is like a heavy train on a railway. The 




FIG. 337. — SENDING APPARATUS AND CLOSED RECEIVER, PRODUCE EXCHANGE LINE, 
POSTAL STATION H, NEW YORK CITY. 



carriers used in the small tubes are stopped by allowing them to strike some 
solid object, which can be done without injury to them, but the large carriers 
used in 6 and 8-inch tubes must be brought to rest gradually by means of an 
air cushion, and this involves the use of automatic receiving apparatus not re- 
quired in the small tubes. The more important problems that had to be solved 
in designing the system of 6-inch tubes were the sending apparatus, the receiving 
apparatus, the carrier and the tubes. This was for a line of two stations. When 
intermediate stations are used the problems of switches and automatic receiving 
apparatus to select carriers at their destined stations had to be met. 

The first double line of tubes built in Philadelphia was laid from the main 
Post-office, Ninth and Chestnut Streets, along Chestnut Street to the sub-Post- 



874 



USE. 



office, now located in the Bourse, a distance of about 3,000 feet. The tubes were 
made of cast-iron water pipe, bored upon the interior to an exact diameter of 6% 
inches. The lengths were joined together by making a counter bore at the bot- 
tom of the bells, into which the machined end of the adjoining length fitted, and 
filling the bell with yarn and lead caulked in the usual manner. 

Where it became necessary to turn corners seamless brass tubing was used, 
bent to a radius of not less than 6 feet. The tubes were simply buried in the 
ground, one above the other, at a depth varying from 3 to 10 feet, depending upon 
the location of other underground construction, such as water and gas pipes, 
conduits, sewers, etc. 

The line was, and still is, operated by an air compressor located in the 
basement of the main Post-office. This compressor is of the duplex type, built 
by the Clayton Air Compressor Works, and does not differ, except in relative 
size of cylinders, from the compressors on the market for general purposes. It 




FIG. 338. — DIAGRAM SHOWING THE PRESSURE AND VELOCITY OF THE AIR IN A 

PNEUMATIC TUBE 1 



developes about 25 horse-power and compresses about 800 cubic feet of free air 
per minute to a pressure of 7 pounds per square inch. The dispatching and re- 
ceiving apparatus is located on the main floor of the Post-office near the cancelling 
machines, and in the rear room of the sub-Post-office in the basement of the 
Bourse. 

The tubes are in operation from nine o'clock in the morning until seven in 
the evening, excepting the noon hour. 

The air current flows continuously from the main Post-office to the Bourse 
through one tube and returns to the main Post-office through the other, thus 
forming a loop with the return end connected to the suction pipe of the com- 
pressor at the Post-office. There is an opening in the tube to the atmosphere 
near where it is connected to the compressor, so that the entire circuit contains 
air at a pressure above the atmosphere. 

. It is a pressure system rather than a vacuum system, as these terms are 
commonly understood. 



USE. 875 

Carriers occupy sixty seconds in transit from the Post-office to the Bourse 
and fifty-five seconds for the return trip. They can be dispatched at six-second 
intervals, or ten per minute in each direction. 

This 6-inch tube has been in operation for five years and is doing good 
service to-day. 

Not content with this the promoters of this enterprise decided to go one 
step further and build an 8-inch tube. 

The second line was laid in New York City between the main Post-office 
and branch Post-office P, in the Produce Exchange Building. It is similar in 
method of operation to the first Philadelphia line, but somewhat longer, the dis- 
tance between stations being about 4,000 feet. Some improvements were made 
in the sending apparatus, utilizing the air pressure to do what was formerly done 
by manual labor. See Figs, 336 and 337. 

When this Produce Exchange circuit was opened for business the con- 
struction of a second circuit was well under way in New York, extending from 
the main post-office to branch post-office H, on Forty-fourth Street, near the 
Grand Central Depot, a distance of 3^-^ miles, with three intermediate stations on 
the line ; at Postal Station D, Third Avenue and Eighth Street ; Madison Square 
Postal Station, and Postal Station F, at Third Avenue and Twenty-eighth Street. 

The main line of this circuit was opened February 11, but the receiving 
apparatus for the intermediate stations is not yet completed.- This is the longest 
circuit built thus far. The inside diameter of the tubes, like the Produce Ex- 
change circuit, is 8J^ inches. There are two tubes, one for dispatching up-town 
and the other down-town. They are operated by air compressors, located one at 
the post-office and the other at Forty-fourth Street. The time of transit of the 
carriers in either direction is about seven minutes. The air pressure at the com- 
pressors is 13 lbs. 

During the autumn of last j-^ear a circuit of 8-in. tubes was constructed in 
Boston between the main post-office and the North Union Railway Station, a 
distance of about 4,500 feet, or a little less than i mile. This is similar in all 
respects to the Produce Exchange line in New York. It is used to transport the 
outgoing mail from the post-offices to the trains, and the incoming mail from the 
trains to the post-office. 

On Thursday, April 7, a circuit of tubes between the main post-office and 
the Pennsylvania Railroad Station at Broad Street, in Philadelphia, was for- 
mally opened for the transportation of mail to and from trains. Since then an 
intermediate station has been established at the Reading Terminal. The tubes 
are laid from the post-office through Chant Street to Tenth Street, up Tenth 
Street to Filbert .Street, and out Filbert Street to the Pennsylvania station. 

Another circuit has been constructed between the main post-office in New 
York and the main post-office in Brooklyn, by way of Brooklyn Bridge. 

The total length of 8-in. tubing in all these circuits is a little more than 17 
miles. This has all been manufactuied and laid under ground since August i, 
last year. 

THEORY. 

A current of air may be made to flow through a tube by either pumpmg 
the air in at one end under a pressure above that of the atmosphere, or by ex- 



876 



USE. 



hausting the air, thereby reducing its pressure below that of the atmosphere. In 
either case it is the difference of pressure at the two ends of the tube that causes 
the air to flow. Both methods are used in operating the London and Paris tubes, 
and both are used in the cash systems of our large retail stores, but all of our 
large tubes are operated by compressing the air so that the air-pressure in the 
tubes is at all points above that of the atmosphere. The determining of which 
system shall be adopted depends largely upon circumstances. 

In the operation of short lines of tubes all of the machinery and apparatus 
can be concentrated at one point by using compressed air in the outgoing tubes 
and rarified air in the incoming tubes. 

So far as power is concerned, the exhaust method is more economical, be- 
cause nearly all the power is consumed in overcoming the friction of the air in 
the tube, and this friction varies directly with the density of the air. 

There are several reasons why the compressed-air method of operation is 
better : first, if there are any leaks in the tubes and they happen to be laid in the 




FIG. 339. — CROSS-SECTION OF SENDING APPARATUS 



wet ground, water will be drawn in when the air is exhausted, while it will be 
kept out if the air pressure is above the atmospheric; second, air cushions, for 
checking the speed of the carriers when they arrive at a station, are much more 
efficient and effective with compressed air than with rarefied air; third, cylinders 
and pistons used to operate sending and receiving apparatus can be made smaller 
when compressed air is used. 

There are two methods of using the current of compressed or rarefied air 
in the operation of a line, and these are termed the intermittent and constant 
methods. The first consists in storing compressed air in a suitable tank, or by 
exhausting the air from a tank; then when we wish to dispatch a carrier we 
place it in the tube and connect the tube with the tank by opening a valve. As 
soon as the carrier arrives at the distant end of the tube the valve is closed and 
the air soon ceases to flow. When a long interval of time elapses between the 
dispatching of carriers, this is the most economical method of operation; but 
if carriers have to be dispatched frequently, a great deal of time would be lost in 
starting and stopping the air current throughout the whole length of the tube. 



USE. 



877 



||jnder these conditions the second method, which consists in maintaining a con- 
ftant current of air in the tube, and in having the carriers inserted and ejected 
it the ends of the tube without stopping the current of air for any appreciable 
ength of time, is much more rapid and efficient. This latter method is the one 
used in the operation of all our large tubes. The current of air flows continu- 
ously all day, and the carriers containing mail are swept along like boats in a 
rapidly flowing stream. The analogy is quite perfect. The boats obstruct the 
flow of water and check its speed but little. In order to compute the speed with 




FIG. 340. — TIME-LOCK FOR SENDING APPARATUS. 



which the boats will pass from one point to another, we have only to know the 
speed of the stream between those points when no boat is in it. The presence 
of the boats does not change the speed appreciably. So it is with carriers in a 
pneumatic tube; the air flows nearly as rapidly when a carrier is in a tube as 
when there is none. The friction of the carrier against the inner surface of the 
tube creates a slight drag, but it checks the speed of the air only a little. There- 
fore, in order to know the speed with which a carrier will be transported from 
one station to another, we need only to know the velocity with which the air 
flows through the tube when no carrier is present. 



878 USE. 

Let us assume a simple case of an 8-inch tube one mile long, connected at 
one end to a tank in which a constant air pressure of 10 pounds per square inch is 
maintained, the other end of the tube being opened to the atmosphere. 

I have constructed a diagram showing the air pressure at all points along 
the tube (see Fig. 338). The abscissae represents lengths of tube in feet and the 
ordinates air pressure above the atmospheric in pounds per square inch. At the 
tank end the pressure is 10 pounds, at the open end zero, and at the quarter, half 
and three-quarter mile points 7.91, 5.61 and 3.01 respectively. It will be observed 
that the pressure curve is slightly convex upwards. This is due to the expansion 
of the air in the tube. The pressure curve of the flow of water in a pipe is a 
straight line. The fall of pressure along the tube is analagous to the fall of 
level in a flowing stream or to the fall of potential along a wire in which a current 
of electricity is flowing. 

I have constructed another diagram showing the velocity of the air at every 
point along the tube. The abscissae are lengths of tube in feet, the ordinates 
velocity of the air in feet per second. The velocity at the tank end, quarter, half 
and three-quarter mile points and at the opened end is 59.5, 65, 72, 83 and 100.4 
feet per second, respectively. It will be noticed that the velocity of the air in- 
creases as it flows along the tube, and that it increases more rapidly as it ap- 
proaches the open end of the tube. The increase of velocity is due to the expan- 
sion of the air as it flows along the tube, and the expansion results from the fall 
of pressure. The mean of all the ordinates gives us the mean velocity, which 
enables us to compute the time of transit of a carrier through the tube. We can 
also determine from this velocity curve the time of transit between any two points 
on the tube which may represent stations. 

From the velocity with which the air is discharged from the open end of 
the tube we compute the quantity of air that must be compressed per minute. 
The quantity of free air and the initial pressure enables us to compute the horse- 
power required to maintain the current of air constantly flowing. Of course, 
there are numerous factors which enter into these computations which are only 
determined by experiments and experience, such, for example, as the quantity of 
air that escapes from the tube at the sending and receiving apparatus ; the fall of 
pressure of the air in flowing around bends and through the apparatus ; the effi- 
ciency of the air compressor, etc. 

The temperature of the air, from the instant it enters the compressor until 
it is discharged at the open end of the tube, is an interesting and important factor 
in the theory of pneumatic transmission. Since pressures above 25 lbs. per square 
inch are seldom used, the air cylinders of the compressors are not water-jacketed, 
hence the air is heated by compression to a temperature found by measurement 
to be above the theoretical amount that we should expect from thermodynamic 
formulae. The reason for this will be understood when we remember that the 
incoming air is heated by contact with the hot walls of the cylinder. When air is 
compressed to 7 lbs. per square inch, it leaves the compressing cylinder at about 
160 degs. F. We should expect much of this heat to be soon lost by conduction 
and radiation through the walls of the tube, and as the air flows through the tube, 
constantly expanding, it would not be unreasonable to expect considerable reduc- 
tion in temperature by the time it reached the open end of the tube — a tempera- 
ture considerably below that of the atmosphere. Experience teaches us that after 



USE. 



879 



leaving the compressor the temperature of the air falls rapidly, and that the tem- 
perature in the tubes underground is almost constant, being about that of the sur- 
rounding earth. The compression may be considered as adiabatic and the ex- 
pansion as isothermal with a small error. 

The atmosphere at all times contains more or less moisture in a state of 
vapor, and its capacity for water vapor varies directly with its temperature; that 
is to say, the higher the temperature the more water vapor will the air contain, 
and vice versa. The temperature of the air in the tubes is frequently and usually 
lower than the atmosphere out-of-doors, consequently it often happens that 
moisture is deposited upon the interior of the tubes. The quantity is never very 
great, but sometimes the carriers come out of the tube coated upon the exterior 



,iii*«r' 



k,-.,^ 



m^' 



FIG. 341. — SET OF CUT-OFF SWITCHES FOR EIGHT-INCH PNEUMATIC TUBES. 



with a thin film of moisture. We use the same air over and over, thereby avoid- 
ing drawing into the tube large quantities of moisture-laden air. 

Having thus briefly discussed the theory of the flow of air in long tubes, 
we will now consider some of the necessary mechanical -details. Keeping in 
mind our 8-in. tube, i mile long, connected to a tank of compressed air at one 
end and open to the atmosphere at the other, thereby maintaining a constant flow 
of air through the tube. In order to utilize this tube and air current for the 
transportation of mail or merchandise, we must have some means of inserting 
carriers containing the material to be transported into the tube, without the 
escape of air. In other words, we must have some form of sending apparatus or 
transmitter. This might be accomplished by having a section of the tube with 
valves at each end to stop the flow through this section and conduct it through a 
by-pass. A carrier could then be inserted into this section of tube and the valves 
be turned to their normal position. Or, what we find to be more practical is to 
have a section of the tube that can be swung out of line with the main tube to 
receive a carrier and then swung back into line again. This is the form of send- 
ing apparatus that we use in all our 8-inch tubes. The section of tube is swung 



88o USE. 

by a cylinder and piston operated by the air pressure taken from the tube (see 
Figs. ss6 and 339). The attendant has only to place a carrier in the sending 
apparatus and pull a lever. By using two swinging sections of tube, one of 
which is always in line with the main tube, the apparatus is ready at all times to 
receive a carrier. 

In connection with the sending apparatus, a time lock is used to measure 
and determine the time interval between the dispatching of carriers; in other 
words, to prevent carriers being dispatched too frequently. The period varies 
from six to fifteen seconds, depending upon the length of the line. The time 
lock is found necessary to prevent the collision of carriers and to give the receiv- 
ing apparatus time to operate. The time lock consists of a dash-pot filled with oil 




Fig. 342. — (i) Carrier used in the Berlin system; (2) Largest carrier used in the 

London system; (3) Six-inch carrier used in the first Philadelphia 

system; (4) Eight-inch carrier used in New York and Boston. 

and arranged to lock the sending apparatus, except when the piston of the dash- 
pot is at the bottom of its cylinder (see Fig. 340). 

If our receiving station be located at the open end of the tube, then we 
must have some form of receiving apparatus to stop the carriers without shock 
when they arrive. For this purpose we have in our system what we term an 
open receiver. It consists of a section of tube about 4 feet long, closed at one 
end by a sluice gate and attached to the end of the main line. The air flows out 
through slots in the tube just before it reaches the receiver. When a carrier 
arrives it runs into this closed section of tube which forms an air cushion. The 
compression of the air by the stoppage of the carrier serves to operate a small 
to discharge the carrier, the end of the main tube being closed during this dis- 
valve, which causes the sluice gate to be raised by a cylinder and piston located 
above it. When the gate raises the carrier is forced out on to a receiving table, 



r 



USE. 



88i 



the pressure in the tube being just sufficient to do this. The gate is automatically 
closed after the carrier has been discharged (see Fig. 336). 

If our receiving station be located at any other point on the line of the 
tube we cannot use this form of open receiver, for the pressure in the tube is so 
high, as shown on the diagram, that the air would escape with great force, hence 
we must use what we term a closed receiver, consisting of a section of tube 
forming a receiving chamber and air cushion that can be placed in line with the 
main tube to receive the carrier, and then moved out of line with the main tube 
placement. The receiving chamber is mounted upon trunnions and is swung out 
and into line with the main tube automatically by means of a cylinder and piston 
set into operation by the arrival of a carrier. 

At intermediate stations on the main line of tubes we sometimes place an 
automatic receiving apparatus that will stop all carriers passing through the tube, 
and discharge those intended for that station, while all others are sent on in the 




tube. This is accomplished by placing various sized metal discs upon the front end 
of the carriers and having electric contact points at each of the stations set at 
graduated distances apart to correspond with the sizes of discs on the ends of 
the carrier. When a carrier arrives at a station where its disc is of the proper 
diameter to span the distance between the contact points, and thereby close the 
electric circuit, then that carrier will be discharged from the tube ; but if the disc 
is too small to span the distance between the contact points, then the carrier will 
pass on in the tube to the next station, and so on. 

Intermediate stations are usually supplied with cut-out switches, so that 
carriers can be sent directly past the station without entering it. These switches 
are moved by air pressure, controlled electrically from the nearest station (see 
Fig. 340- 

There is no part of this system that has been the object of more thought 
and study than the carrier that contains the mail or other material to be trans- 
ported. It is made of a seamless steel tube 2^,% inches long, closed at the front 



882 USE. 

end by a sheet metal head and buffer, and closed at the rear end by a hinged 
cover provided with a lock (see Fig. 342). 

The body of the carrier is about an inch smaller than the tube through 
which it travels, the space between the body of the carrier and the surface of the 
tube being filled by two fibrous rings that serve not only to prevent the escape 
of air past the carrier, but as wearing surfaces to slide on the lower side of the 
tube. These bearing rings are made of cotton fiber, and they will endure until 
the carrier has traveled about 5,000 miles, when they become worn so small that 
they have to be replaced by new ones. A carrier weighs 13^ pounds and will 
contain 600 ordinary letters. 

The tubes used in all the circuits thus for constructed are of cast iron 
bored accurately upon the interior, except bends, which are made of seamless 
brass tube. The iron tube is cast in 12-foot lengths, with a bell upon one end 
similar to gas and water pipes. A counter bore is turned in the bottom of each 
bell, into which the machined end of the adjoining length fits closely. The joints 
are made by yarn and lead caulked in the usual manner. 

Where short bends have to be made in the tube for the purpose of turning 
corners in the streets, entering buildings, etc., brass tubing is used bent to a 
radius of twelve times the diameter of the tube, or a radius of 8 feet for an 8- 
inch tube. A uniform radius is always used, for it facilitates manufacture. 

In order to maintain a uniform and circular cross-section of the tubes 
during the process of bending they are filled with resin. 

The location of the bearing rings on the body of a carrier also has an im- 
portant relation to the bends in order to give a carrier of maximum capacity. 
Having determined the length and diameter of the carrier body, we place the 
bearing rings not on the ends, but at a point where, in passing through a bend 
of minimum radius, the corners and center of the carrier and the bearing rings 
will touch the walls of the tube at the same time. This can best be explained by 
referring to Fig. 343. The rings C C are so placed that in passing through the 
bend the ends of the carrier touch the outer circumference of the tube at A A, 
at the same time that the body of the carrier touches the inner circumference at B, 
and the rings touch both inner and outer circumferences at D D D D. 

To manufacture the tubes, brass bends, carriers, sending and receiving and 
other apparatus used in the system, a factory has been erected at Tioga and 
Memphis Streets, Philadelphia. Much of the machinery used in the various 
processes of manufacture has been especially designed for the purpose, and most 
noteworthy, perhaps, are the machines for boring the cast iron tubes. The tubes 
are bored in a vertical position, for two reasons: (i) It economizes space; (2) 
the chips fall away from the cutters. 

The boring machines are placed upon galleries about 11 feet above the 
floor. The bell ends of the tubes are clamped to the machines and rest on a 
pedestal on the floor below. The boring is done by six cutters attached to a head 
that is mounted on the lower end of a vertical boring bar. The bar is revolved 
by gearing and fed downward by a screw attached to the cutter head and ex- 
tended downward through the center of the tube being bored. The feed screw 
does not revolve, but is drawn downward by a nut attached to the pedestal on 
which the tube is supported. The nut is revolved by gearing and a rope belt 
driven from the machine above. When a tube is placed in the boring machine 



I 



USE. 



883 



the feed screw is pulled up through it and attached to the cutter head. The bor- 
ing bar simply serves to revolve the cutter head and not to guide it. The cutter 
head is guided by four hardwood blocks that fit the finished bore of the tube 
closely. The pull of the feed screw also helps to keep the cutter head in place. 
The cutters are flat pieces of steel, with a cutting edge at 45 degrees with the axis 
of the tube. The angle of the cutter tends to make the cutter head follow the 
core of the tube. After the bore is finished another head is attached to the bar, 
which makes the counter bore at the bottom of the bell. 

A special machine has been designed for bending the brass tubes, con- 
sisting of three rolls, one of which is adjustable. This operation of bending is 
one that requires much experience and skill on the part of the operator. 

Locating Obstructions. — You will, perhaps, be interested in an experiment 




FIG. 344. — CHRONOGRAl'H 



L'^Kl) IN PHILADELPHIA FOR 
PNEUMATIC TUBES. 



LOCATJNC. ()15STKLH:T10NS IN 



that we made in Philadelphia two years ago to locate a carrier that became lodged 
in one of the tubes. 

The Philadelphia line was laid in the winter season, and before the trench 
was back-filled the loose earth became frozen and we were obliged to put it into 
the trench in that condition ; consequently, when the ground thawed the tubes 
settled and one of them was broken. For a long time this break did not obstruct 
the passages of carriers, but eventually one of the broken ends settled down 
more than the other and caught one of the carriers, blocking the entire line. We 
had no means of knowing where the break was located, and to excavate the entire 
distance between the stations involved great expense and annoyance. I made 
several attempts to locate it by the fall of pressure, etc., but was not satisfied with 
the results, so decided to try a method of locating by the velocity of sound. 

The plan was to disconnect the terminal apparatus at one of the stations, 
fire a pistol into the tube, and note the time that elapsed between the discharge 



884 USE. ■ 

of the pistol and the return of the sound as an echo reflected back from the ob- 
structing carrier ; then, knowing the velocity of sound, a simple calculation would 
give us the distar-ice from the station to the carrier. 

I had a rough chronograph constructed, using a pulley for a drum, mounted 
upon a horizontal shaft with a crank for rotation and a screw to give longi- 
tudinal motion (see Fig. 344). Time was measured by the beats of a clock pendu- 
lum, recorded on the chronograph drum by a stylus which moved under the pull of 
an electro-magnet at each beat of the pendulum. The pendulum was arranged to 
close an electric circuit in the usual manner by swinging through a globule of 
mercury. In addition to the clock a tuning fork was used to measure time by the 
number of waves traced on the smoked surface of the drum. For the measure- 
ment of small fractions of a second the tuning fork is more accurate and con- 
venient than a clock, but when the period extends over several seconds the work 
of counting thousands of small waves becomes very laborious. 

I selected a fork tuned to 512 vibrations per second, which enabled me to 
measure to i-iooo of a second with a small error. In fact, with a little care, it 
was possible to measure to 1-5000 of a second. 

The fork was arranged in a horizontal position, having a horse-hair 
cemented to one prong, which traced a sinuous line on the drum as the latter was 
turned. The sound of the pistol discharge was recorded by a stylus attached to 
the end of an aluminum arm that rested against a rubber diaphragm. A chamber 
in the rear of the diaphragm was connected to the end of the pneumatic tube by a 
piece of rubber hose which conveyed the sound waves from the tube to the chro- 
nograph. A cock was placed in the middle of the hose and partially closed be- 
fore the pistol was discharged to prevent too great distention of the diaphragm 
by direct impact of the sound waves. The cock was opened by an attendant after 
each discharge and before the echo returned, in order that the feeble sound 
waves of the echo might not fail to be recorded. 

The muzzle of the pistol was inserted into the tube through a small hole in 
the side, the end of the tube being closed by a funnel to which the rubber hose 
was connected. 

When the apparatus was properly adjusted a measurement was taken in the 
following manner: The clock was started, the tuning fork set in vibration by 
striking with a mallet or by bowing, and the drum rotated by hand; then the 
pistol was discharged and the cock in the rubber hose opened. A few moments 
only were required to count the waves of the tuning fork and from them com- 
pute the time. 

The experiments were usually repeated several times to eliminate errors. 
Five experiments gave the following results: 

1 2.79T seconds. 

2 2.794 

3 2.793 

4 2.793 

5 2.794 " 

Mean 2.793 " 

A thermometer was placed in the ground beside the pipe and the tempera- 
ture found to be 39 degrees. It was assumed that this was the temperature of the 



USE. 885 

air in the tube. The velocity of sound at 32 degrees was assumed to be 1,093 feet 
per second, and the increase of velocity for each degree of temperature to be 1.12 
feet; this gives at 39 degrees the velocity of 1,101 feet per second. 

In 2.793 seconds the sound would travel 3,075 feet, which locates the car- 
rier at 1,537 feet from the instrument. This indicated that the carrier was 
lodged 100 feet east of Seventh Street, and workmen were ordered to excavate 
at that point. Before reaching the tube air was heard escaping from the break, 
and the carrier was found almost exactly where it had been located by the in- 
strument. 

It is impossible to say what the limits of the method are so far as distance 
is concerned, but experiments of Regnault show that the report of a pistol is no 
longer heard at a distance of — 

1,159 metres in a tube 0.018 m. in diameter. 

3,810 " " " 0.300 " 

9.540 " " " i.ioo " 

But the same sound waves will vibrate a sensitive diaphragm at distances 
of 4,156, 11,430 and 19,851 metres respectively. b. c. bacheller. 



PNEUMATIC DESPATCH TUBE SYSTEM IN THE ILLINOIS TRUST 
AND SAVINGS BANK BUILDING, CHICAGO. 

A few years ago a banking institution was thought to be complete if it had a 
good fire and burglar-proof vault and a trust-worthy clerk to remain in the build- 
ing during the night. As the years have passed improvements have been made, 
such as the time lock for vault doors, and now a secondary door with a time lock 
has been adopted as an extra safeguard in case the larger door fails to unlock. 
In other cities where they have the protective associations, the electric alarm sys- 
tem has been applied. Later came the telephone service, with a small central sta- 
tion in the building, connected with an instrument on the desk of every official, 
important clerk, and the heads of diflferent departments, and also with the city 
central station. As a final improvement pneumatic tubes have been adopted. This 
necessity was first recognized by the First National Bank of Denver, next by the 
National Bank of Commerce in New York, and then by the Illinois Trust and 
Savings Bank of Chicago, where they have a complete equipment throughout 
their large building into which they have moved. 

By the adoption of the pneumatic tube system, the officers, heads of depart- 
ments, tellers and important clerks are in immediate communication with one 
another ; that is to say, when a customer appears at the draft teller's window and 
a.«;ks for a draft, the same is made out, but he is not met with the familiar phrase, 
"Kindly step down to the vice-president or cashier with this draft and he will 
sign it." Instead, he waits just a moment while it is sent through the tube to the 
proper person, who signs it without delay and returns it to the teller ready for 
the customer. He is thus saved the bother of the trip to the vice-president; like- 
wise the latter is saved the usual talk about the weather and business in general, 
which in most cases is not very much appreciated. The pneumatic tube system 
also saves the paying teller the trouble and time of ascertaining from the presi- 



886 



USE. 



dent or cashier of the institution if a certain check is acceptable. All he has to 
do is to put the check in the carrier, dispatch it to the president's station and it is 
immediately returned to him with the O. K. or otherwise, upon it. 

In citing the cases above, I showed briefly how the pneumatic tube system 
overcomes loss of time, bother and annoyance. I will now endeavor to give a brief 
description of the plant installed for the Illinois Trust and Savings Bank. In this 
particular instance the arrangement of the system was not decided upon imtil the 




FIG. 345. — ELECTRIC 'DRIVEN AIR COMPRESSOR. 



building plans were too far advanced to make any alterations which would facili- 
tate the construction of the tube system, therefore it was necessary to lay out the 
plant to the best advantage of all concerned under the existing circumstances. 
The work of designing, as well as installation, fell upon the writer. After ascer- 
taining from the officers of the bank how they handled their business — that is, 
what offices were to be connected— the next question was regarding the size of 
package to be sent through the tubes. It was finally decided that a bond would be 
the maximum size which would go into a carrier, the measurements being 9 inches 



r 



USE. 887 



long and internal diameter i^ ins. Then came the question whether or not the 
tubes could be laid under the floors and all concealed. After going into the mat- 
ter very thoroughly, it was found that 2}-k" outside diameter tubing could be laid 
in this way. As a result contracts were drawn up and signed for the following: 
Ten lines of 2%" o. d. tubes, No. 19 Stubbs gauge, connecting the following 
offices and departments : 

President and Secretary. 

President and Vice-President. 

Vice-President and Draft Teller. 

Cashier to Collections. 

Cashier to Foreign Exchange and Bond Teller. 

Cashier to Draft Teller. 

Assistant Cashier to Collections. 

Assistant Cashier to Foreign Exchange and Bond Teller. 

Assistant Cashier to Draft Teller. 

Collections to Trust Department. 

As the building progressed the system was installed about as follows : 

In the basement is located, adjoining and jointly with the sewerage disposal 
system, a two h. p. motor of the Crocker- Wheeler type (shown in Fig. 345), with 
a speed of 700 revolutions, running an 8 x 10 Ingersoll-Sergeant Compressor, at a 
speed of 100 revolutions. The necessary governing devices are controlled by the 
air pressure in the receiver or reservoir, the size of which is 4 ft. by 8 ft. The 
minimum pressure carried is 6 pounds, maximum 9 pounds. There are two air 
supply pipes leading to this reservoir, one on the south side and the other on the 
north side of the building. Ihe diameter of these pipes is two inches, and they 
are reduced down proportionately until they reach the last station on their re- 
spective sides of the building. At different points along the line of these supply 
pipes ^" diameter feeders are connected running to the several stations. The 
flooring in thq corridors is marble, under which is a t-Yz" cement foundation, there- 
fore two coats of asphaltum varnish was given all the pipes to prevent chemical 
action. The machinery once ready for operation, supply pipes and feeders were 
installed ; then the work of laying the carrier tubes was commenced, part of the 
latter being laid in cement and part in cinders. The joints were made by means 
of sleeves and clamps, the former being well cemented to the pipe with shellac, 
making them absolutely air-tight. 

The extra length of carriers and short turns called for a special curve made 
ot cast iron, the radius of which was 15", enlarged in the centre so as to admit the 
easy passage of the carrier, shown in Fig. 346, and at the same time overcoming 
the difficulty of getting around sharp corners without cutting through the marble 
floor and wainscoting. 

To prevent any possible damage to the tubing during the construction of the 
building by the workmen employed outside of our own, the tubes were tested 
each day by means of a small positive pressure blower, a carrier being forced 
through first one way and then the other. As soon as any obstruction was dis- 
covered it was immediately located, a short section removed, and if necessary new 



888 



USE. 



pieces substituted. It was generally found that these obstructions were dents 
caused by falling timber or sections of tile. In several instances the carpenters 
had driven nails through the tubing. 

Fig. 347 shows the terminals in the office of the cashier and assistant 
cashier. Their desks (not shown in the cut) are located adjoining the cabinet on 
which the terminals are placed. 

The operation of this system is about as follows: 

The carrier is placed in the tube at the terminals, and the door, a sliding one, 
is closed, which opens a valve admitting air into the dispatch tube from the sup- 



Z51. 




T57 ^57 

FIG. 346. CURVE IN PNEUMATIC CARRIER SYSTEM, 



ply pipes, thus forcing the carrier through the tube to the other end, at which 
point it is discharged and falls on top of the cabinet for the purpose. As the car- 
rier passes out of the terminal at the extreme end, it automatically closes an 
auxiliary door behind the carrier. This door closes the dispatch tube to the atmos- 
phere, and therefore prevents the compressed air in the tube from escaping. The 



USE. 889 

sudden stopping of the flow of air produces a pressure upon the diaphragm lo- 
cated in the terminal from which the carrier w»s dispatched. The diaphragm 
releases the valve, cutting off the air supply and at the same time opening a vent 
underneath the terminal, which allows the confined air in the dispatch tube to 
escape underneath the desk. In a second's duration the air has escaped and the 
door at the sending end of the tube, as well as the auxiliary door at the receiving 




FIG. 347. — TERMINAL STATION OF PNEUMATIC DESPATCH. 



end, opens and goes back to the normal position. The tube is then again ready for 
the sending of a carrier in either direction. The diaphragm controlling the valve 
in the supply pipe is regulated according to the length of the line. From test it 
shows that a speed of about 30 ft. per second is attained. 

This system is known as the Automatic Pressure System, and differs from 
the continuous current or vacuum system in that only one carrier tube is used 



890 USE. 

instead of a pair, and the air is compressed and stored in reservoirs or tanks and 
only used as needed. In this particular design of system the writer claims the 
following over other designs installed by him as well as others : 

First — That the air confined in the dispatch tubes after the discharge of the 
carrier is allowed to escape underneath the cabinet on which the terminal is placed, 
thus doing away with the objectionable noise in the room, the blowing away of 
papers if such should be left on the cabinet. 

Second — In sending a carrier the door closes the tube to the atmosphere 
before opening the valve admitting air from the supply pipes. 

Third — The valve action is absolutely positive. 

On account of the high pressure maintained in the reservoir, the consump- 
tion of air is great, but the three difficulties overcome by this design outweigh the 
small extravagance. edmund a. fordyce. 



AN OLD UNDERGROUND PNEUMATIC TUBE. 

At a meeting of the Langbourn Ward Club, held last night at the London 
Tavern, Fenchurch street, Mr. George Threlfall read a paper on the old under- 
ground pneumatic tube that runs from the General Post Office to Euston Station. 
The tube was built forty-two years ago for the purpose of conveying mails, 
parcels, etc., by pneumatic despatch. It was made of cast-iron sections an inch 
thick, was 4 feet high by 4V2 feet wide. The old Pneumatic Despatch Company, 
which was founded in 1859, was obliged to cease working because it was found 
that the system of blowing or sucking the cars through the tunnel by air pressure 
or vacuum was impracticable, owing to leakage of air and other mechanical 
defects. Mr. Threlfall said it occurred to him that if the tube were still avail- 
able it might possibly be utilized for its old purpose if worked by electric trac- 
tion. The tube had been closed for so long that all the plans and records of it 
seemed to have been lost, and it took practically three years to collect sufficient 
information and plans to enable him to draft a feasible, if not a perfect, scheme.- 
Speaking of the arrangements to be adopted. Professor Carus Wilson said one 
unique feature was that the cars would be controlled from a central station, as 
the tube was too small to admit of drivers going with the trains. The man at 
the central station would be able to see from an indicator the precise position 
of a train at any moment, and to make it go quicker or slower or to reverse 
it as he wished. The speed would be between thirty and forty miles an hour.— 
Pall Mall Gazette, Oct. 5, 1899. 

This story of a forgotten tunnel has recently been discussed in the London 
newspapers, and has excited considerable interest. It seems to have passed out of 
the minds of the people, and to have been quite as quiescent and forgotten as 
the old North River tunnel in America, bored three-quarters of the way across 
the Hudson by Colonel Haskin and English engineers. 

Readers of Compressed Air will recollect an illustration and brief notice of 
this tunnel in Volume 2, No. i, published in March, 1897. It seems to have been 
one of the earliest notions in the use of pneumatics to propel parcels by com- 
pressed air in a closed tube. About two centuries ago the idea was discussed by 



USE. 891 

le celebrated Dr. Papin. In the year 1810 a proposal was made by Medhurst — 
the Danish engineer — to put parcels and passengers in a canal 6 feet high and 5 
feet wide, the propelling power being atmospheric air affected by rarefaction and 
condensation. Later on, an Englishman named Vallance in the year 1824 made a 
similar suggestion, his plan being to connect Brighton and London by means of a 
pneumatic tube of such size as to admit carriages ; but these suggestions were not 
put into practical operation until about the year 1865, when the recently discovered 
London tube was built. The engineer was a Mr. Rammel, whose plans were to 
exhaust the air from one end of the tube by means of fans. Whatever may have 
been the cause for the failure of these plans, it is very likely that the experiment 
was tried on too large a scale. It seems to us to be a similar case to the attempt 
recently made to run cars on the New York Elevated Railroad by compressed 
air. The aim was too high, it being an eflort to accomplish a result on a large 
scale without having first had experience in the same direction on smaller lines. 
All great engineering results are brought about by a course of gradual develop- 
ment. Experience and a close study of that experience developing a system from 
small things to larger things, is the true way to success. 

Since this experiment in London we have seen pneumatic tubes put to prac- 
tical operations in several cities. The Petit Bleu, so useful in Paris for quick mail 
service, is a pneumatic tube system, and in New York city mails are conveyed up- 
town and across the bridge to Brooklyn through the Batcheller pneumatic tubes. 
This Batcheller system is the largest which we have at present; but even here 
the tubes are only about 8 inches in diameter, and it is very likely that the success 
of this system, which is now generally admitted, will result in the laying of tubes 
of larger sizes until, perhaps, we may do what was attempted in London nearly 
40 years ago. 



TRANSMISSION THROUGH PNEUMATIC TUBES. 

The writer having been employed in designing the extension of a pneumatic 
dispatch line, in which some heavy gradients were unavoidable, it became neces- 
sary to ascertain by calculation the steepest gradient that could be employed so as 
to obtain sufficient carrying capacity in the new section of the line under given 
conditions of engine power and of length. Almost every text-book and paper 
on the velocity of gases in pipes, gave a different formula, and the author there- 
fore found it necessary to attempt to construct a convenient expression for the 
speeds of carriers of given weight and friction, under various conditions of pres- 
sure, gradients, and dimensions of tube. The problem of a pneumatic system is 
simply this: To make a given quantity of air expand from one pressure to an- 
other in such a way as to return a fair equivalent of the work expended in com- 
pressing it. It is obviously impossible to regain the full equivalent of the work, 
because the compression is attended with the liberation of heat, which is dissi- 
pated and practically lost. Therefore, in designing a pneumatic system, the first 
thing is to contrive means of compressing the air as economically as possible; 
and, in the second place, to get back the available mechanical effort stored up in 
the compressed air; irrespectively of the work employed in compressing and ex- 



892 USE. 

amining it. The writer considers that small pneumatic tubes may be worked 
more profitably than large ones. The great convenience of and the practical 
facilities for working small letter-carrying tubes have been amply proved by the 
extensive systems already laid down in Paris, Berlin, London and other towns, 
as adjuncts to the telegraph services. Tubes of somewhat larger diameter would 
undoubtedly work satisfactorily. Even still larger tubes, of a moderate length, 
might also be found useful for a variety of special applications. But the author 
does not believe that a pneumatic line working through a long tunnel could, for 
passenger traffic, ever compete in point of economy, with locomotive railways. 
A pneumatic railway is essentially a rope railway. Its rope is elastic, it is true, 
but it is not light. Every yard run of it in a tunnel large enough to carry pas- 
sengers, would weigh more than % cwt. And it is rope, too, which has to be 
moved against considerable friction, and in being compressed and moved wastes 
power by its liberation of heat. In a pneumatic tunnel, such as that proposed 
between England and France, in order to move a goods train of 250 tons through 
at the rate of 25 miles an hour, it would be necessary to employ simultaneously 
a pressure of i^ lbs. per sq. in. at one end, and a vacuum of i>^ lbs. per sq. in. at 
the other. The mechanical effect obtained of these combined — pressure and 
vacuum — would be consumed as follows : 

In accelerating the air 29 ^ 

In accelerating the train 12 (^ millions 

By friction of the air 5721 ( of foot 

By friction of the train 330) pounds. 

The resistance of the air, therefore, upon the walls of the tunnel would 
alone amount to 93 per cent, of the total mechanical effect employable for the 
transmission ; while the really useful work would be only about 5^2 per cent, of 
it. And to compress and exhaust the air to supply these items of expenditure of 
mechanical effect, engines would have to exert over 2,000-horse power at each 
end during the transmission, even on the supposition that the blowing machinery 
returned an equivalent of mechanical effect such as has never yet been obtained. 
This would not be an economical way of burning coals. — Journal of the Tele- 
graph. 



IMPROVED PNEUMATIC TOOLS FOR FOUNDRY USE.* 

The use of pneumatic tools for cleaning and chipping castings is not new. 
Certain defects in the old style of construction, the want of knowledge of how to 
operate them, together with the prejudices of ignorant workmen, have resulted in 
eight cases out of ten in the condemnation of the tools for foundry use. The 
first thing we will deal with will be the objectionable features of the old style of 
tools, of which the recoil or kick was the most noticeable. This recoil or kick 
has done more to prevent the adoption of large size pneumatic tools than anything 
else, as it has enabled the workman who is afraid of losing his place to say with 

*A paper read by Mr. George H. Robbing (Philadelphia! at the January, 189H, meeting of the 
Foundry Men's Afesociation. . > » & 



USE. 893 

sbme appearance of truth, that holding the tool was injurious to him, producing 
a paralysis of his arm, etc. To this, and here, let me reply that I know of men 
who have been running pneumatic tools continuously for the past five years and 
who have not been affected in the slightest by them in any way whatever. The 
improved Clement valveless tool is so constructed and so evenly balanced that 
all kick has been eliminated from it, because it has an air cushion so placed that 
when in operation the workman is really pushing against air, the elasticity of 
which takes up all shock and vibration. 

Another important objection that is made to the old style pneumatic tool is 
that so many small parts, valves, springs, etc., enter into its construction. Such 
a number and variety of parts make the tool very delicate and liable to get out of 
order. 

The improved Clement valveless tool consists of but three parts or pieces — 
a cylinder that is bored out of a solid piece of steel, a hammer or piston made of 
tool steel and a butt piece or plug to close the end of the cylinder. The only part 
of it that moves is the hammer, and that is not dependent on the movement of any 
other part for its own motion. If it is given fair treatment and regularly oiled, it 
can be depended on for a long period of steady and reliable service, and knowing 
this we are warranted in guaranteeing it against all repairs for two years. This, 
I trust, shows plainly and conclusively to any investigator that the objectionable 
features in the pneumatic tool of the past are not to be found in the improved 
Clement tool of to-day. 

Let me now speak a moment of the ignorance of operating, and the preju- 
dice existing against pneumatic tools and the reason therefor. No doubt some 
of you have had pneumatic tools tested in your foundries and perhaps unsuc- 
cessfully. Have you, however, considered in such a case how this test was made ? 
Pneumatic tools are made in many sizes, and to use them to advantage they must 
be used for the purpose to which they are adapted — that is, a small tool for light 
work and a large tool for heavy work. Then again, at what air pressure did you 
try this tool? Do you know whether the pressure used was high enough to 
develop the efficiency of the tool ? And last, but not least, in whose hands was the 
tool placed for trial V Was he a man who would work for your interests, for- 
getting his own, or was he opposed to the tool because it was a labor-saving 
device, and because its adoption was liable to bring about the discharge from em- 
ployment of himself or some of his shopmates? These are all-important con- 
siderations, and may explain to you why the test of pneumatic tools in your shop 
was a failure, if such it was. 

The best way to introduce the tools is to place them in the hands of young 
men, who are, as a rule, ambitious, and who will take a pride in running a new 
machine. Let them know that the successful operation of the tool will mean a 
slight advance in their wages. If on the contrary, however, you give tools to a 
man who believes only in old hand methods, then the amount of work that he will 
turn out will' be, comparatively speaking, small. 

The average amount of work that can be done with these tools is as follows : 
In removing sand from large and heavy castings, one man with a medium size tool 
and a broad chisel, can readily do as nuich work in a given time as six men could 



894 USE. 

do by hand methods. One man with a tool can do as much light fine chipping 
as is usually done by five men in the same period of time; and in rough 
or heavy chipping one man with the proper size tool can do about the same 
quantity of work that is generally done by three or four men with the ham- 
mer and chisel. 

It is sometimes necessary to do chipping to a line, or true surface. A man 
who is skillful enough to do this class of work with a hammer and chisel can 
accomplish just twice as much in the same time by using a pneumatic tube for 
the purpose. The operator has absolute control over the tools used for this fine 
work, striking a light or heavy blow as he desires, governing the force of the 
blows by the simple pressure of his hand, and not by throttle valves, etc., that 
are so liable to wear out. 

If any one should doubt the possibility of the operator being able to cut to 
a line, or having this perfect control over the tool, it affords me pleasure to refer 
you to the marble and granite cutter, who not only does the most delicate carving 
and lettering with the tools, but does it on a substance that is vastly more friable 
and brittle than cast iron. 

An air compressor, and an air receiver, and a lot of different sizes of pipe 
strung around the shop do not always constitute either an efficient or economical 
air plant; To get the best results there is required : 

1. An air compressor of improved pattern, of sufficient size and power to 
develop and maintain a steady pressure of 80 to 100 pounds to the square inch. 

2. An air receiver of sufficient size to equalize the pulsations of the com- 
pressor and to cause the air to flow with uniform velocity to the tools. 

3. As air in its passage through the pipes is subject to friction in the same 
manner as water, it is important that your pipe system be carefully designed, as 
loss by friction may be quite serious. In calculating such loss it would be well 
to remember that the difference in pressure between the entrance to the pipe and 
the point of use, termed in hydraulics "loss of head and power lost," is not 
applicable to compressed air. Compressed air will lose 10 per cent, of its head, 
but the loss of power will only be about 3 per cent. The reason for this is simple 
when you remember that compressed air as it loses in pressure it gains in bulk, 
and thus in a measure by its increased volume compensates for the diminished 
pressure. 

DISCUSSION. 

Mr. Howard Evans — You do not mention the amount of power required to 
drive the compressor, nor state the saving over hand work where the tools are 
used. You only say that one man can with one tool do so much more work than 
by hand. 

Mr. Robbins — An air compressor of a size sufficient to operate say three 
tools, 14-ounce hammers, would require 4 horse power to run it — that is, a belt 
compressor. When a small compressor can be used it is much more economical 
to run it by belt power than by steam direct. The cost of such a compressor 
would be in the neighborhood of $180. The cost of the air receiver would be 
about $40, while the cost of the pipe would depend altogether on the distance the 



r 



USE. 895 



air was to be carried; if 100 feet, say $5. Three tools of the capacity mentioned 
would cost say $300. A total cost of about $525 for the equipment. 

Mr. Evans — Where people have a compressor in already the adoption of 
these tools is accompanied by considerable less expense, is it not? 

Mr. Robbins — Certainly. I have here a small 2-ounce tool, the earning 
capacity of which is $900 per annum. That is the earning without the expense. 
The tools actually save the labor of one man for 300 working days in the year. 
The outfit I have mentioned is large enough to run six of these tools. In taking 
sand off castings you would require a broad chisel like this (showing a chisel 
with about 2-inch cutting edge). 

Mr. Messick — Are the tools in use in this city? 

Mr. Robbins — Yes. They are used at Cramp's, and at the works of the 
Warden Manufacturing Company, in both boiler shop and foundry. They are 
used in ship-yards for chipping and calking. When used for calking a man can 
a man can calk 60 lineal feet per hour ; on boiler work about 40 feet. It makes a 
tighter joint than is possible by hand, the blows not being so hard, but multitudi- 
nous. The tool I have shown you uses 10 feet of air per minute at 80 pounds pres- 
sure. It can be operated with a pressure as low as 60 pounds, but high pressure 
is the best, the resulting work being much more efficient. 

Mr. Messick — Did you ever try driving rivets with them? 

Mr. Robbins — Yes; what you call shell rivets; ^-inch cold rivets. A 6- 
pound hammer will drive them faster than you can put them in the hole. 

Mr. Eldridge — Supposing one wished to knock off a riser from a casting, 
say a riser 2 inches in dfemeter, would you smooth the casting with the tool as 
well? 

Mr. Robbins — A sledge would be better for knocking off a gate of that size. 
After the gate is knocked off you can smooth down with the pneumatic tool. 

Mr. Evans — Supposing a foundryman having a compressor wished to try 
these tools, would you give him a trial ? 

Mr. Robbins — Certainly. He could have them for ten days on trial, and 
we would visit his foundry and impart all instruction possible. 



PNEUMATIC TOOLS. 



The pneumatic tools now being manufactured and put on the market by the 
Philadelphia Pneumatic Tool Company, of Philadelphia, have many important 
and novel features. 

Taking up the several kinds of tools made by them in the order of their im- 
portance and wide range of work for which they are adapted, we have first the 
Chipping and Calking Hammers. 

These hammers are made in five sizes, the smallest being designed for light 
chipping and calking, and the largest for the heaviest kind of work, such as 
chipping steel castings, cutting off gates, sink heads, etc. 

These hammers are all of the "valve" type. 



896 USE. 

There are only two moving parts in the hammer, the hammer proper and the 
valve, both moving in the same direction at the same time, so that the jar caused 
by the hammer striking a blow tends to more firmly seat the valve and not to 
move it from its seat. This insures uniform working of the hammer, even after 
it has been worn after years of service. 

The material used is of the very best, and the valve hardened and carefully 
ground and fitted. 

For riveting two sizes of hammers are made, the smallest one driving ^-inch 
hot rivets and under, and the largest, or Long-Stroke Hammer, driving i>^-inch 
hot rivets. The design and construction of the valves of these hammers is the 
same as in the Chipping Hammers, thus avoiding the irregularity of action due to 
the wearing of the valve. 

The Long-Stroke Hammer, by an ingenious arrangement, ceases to operate 
as soon as the die is lifted from the rivet, although the throttle valve may be 
open ; this avoids any unnecessary wear or liability to breakage which may occur 
should the hammer operate when the die is not held against some object. Other 
important changes and improvements have been made. ♦ 

ROTARY DRILLS. 

Probably the most trying work on Pneumatic Tools is the drilling, reaming 
and tapping of holes in boiler, bridge and car shops. The work is rushed through 
by unskilled workmen, and the tool, to do it successfully, must be carefully de- 
signed, strongly built and simple in construction. These features have been em- 
bodied in the drills made by this company, and are the result of years of experi- 
ence in their design and manufacture. They are built for the hardest service, but 
at the same time are finished with a high grade of machine work equal to the 
other work done by this company. The drills have improved piston blades, fitted 
with packing strips that require no attention to keep them tight. These are so 
made that as the machine is used the bore of the cylinder acquires a glassy polish 
similar to that found in steam engine cylinders. For convenience in tapping, 
flue rolling, etc., these drills are made reversible. 

FOUNDRY RAMMERS. 

One of the important steps recently made by this company in introducing 
labor-saving tools has been the introduction of their Foundry Rammers. With 
this tool one man can do the work of four or five men, besides ram up a flask 
much more evenly, and thus reduce the risk of bad castings or increased weight 
from straining to a minimum. At present they are making the rammers in three 
sizes; the No. 7 or Light Hand Rammers, the No. 8 or Heavy Hand Rammer, 
and the No. 9 or Crane Rammer, to be used suspended from a crane. 

The No. 7 Rammer is designed for flask work, and ramming in limited space 
where a large rammer cannot be used. The No. 8 is especially built for loam 
work and ramming up very large flasks. 

The advantages of these rammers are as follows : They .strike a uniform 
blow, work at a uniform rate, one man with a No. 8 Rammer can do the work 
of six or eight men, and with a No. 9 Rammer the work of from twelve to fifteen 
men and do it better, more evenly and harder. 



kM2l 



USE. 



897 



Where these rammers are in use they have paid for themselves in a short 
time, and many duplicate orders have resulted. They are now in use in some of 
the largest foundries in the country. 

The Pneumatic Riveting Machine illustrated below is adapted to a wide range 
of work on tanks, stacks, bridges, ship framing, structural work, etc. It will 
drive rivets of any size up to i5^-inch, and may be used with any depth of yoke, 
from 10 inches to 10 feet or more. 

The Riveter itself presents many improvements in design. It is absolutely 
positive in its action, no dependence being placed on springs or other similar de- 
vices. The entii-e action of the machine is under the control of the operator by 
means of one throttle lever shown in the illustration. The first movement of the 
lever causes the hammer cylinder to move out against the rivet; the next move- 




FIG. 348. — YOKE RIVETER. 



ment starts the hammer to work upon the rivet. When the rivet head is com- 
pleted a reverse movement of the lever causes the hammer to stop working and 
the cylinder to withdraw into the casing by air pressure. The advantage of this 
arrangment is that the cylinder may be moved out until the button set comes in 
contact with the hot rivet and held there while any necessary adjustments are 
made before starting the hammer to work. This will, in many cases, prevent 
spoiling the rivet and necessitating cutting it out. The withdrawal of the cylinder 
into its casing by means of air pressure enables the operator to use the machine 
in any position with the certainty that the cylinder will positively remain inside 
the casing until he is ready to drive the next rivet. These points will be appre- 
ciated by those who use machinery of this kind. 

The machine is light in weight and simple in construction, having but three 
moving parts. It is fully guaranteed as to efficiency and durability. With each 
machine we furnish two riveter dies and one holder on die, with necessary collars 



898 



USE. 



for adjusting the gap for different lengths of rivets. The machine requires 25 cu. 
ft. of free air per minute for operation and ample facilities are provided for thor- 
oughly oiling all parts. Users of this class of machinery will find this Pneumatic 
Yoke Riveter to be a first-class machine, unequaled in material, workmanship and 
efficiency. 

On field work, erecting large water, gas and oil tanks, 80 to 100 rivets per 
hour have been driven. 



i 



COMPRESSED AIR DRILLING MACHINE. 

Our outside cover illustration this month is a compressed air drilling 
machine made by the C. H. Haeseler Co., of Philadelphia. Several machines of 




FIG. 349. — PNEUMATIC RAIL DRILLER. 



this type are used by the Union Switch and Signal Co., for the purpose of drilling 
the ends of rails in railroad yards where compressed air is available. 

The machine has a capacity for drilling holes up to 7/s," in diameter and will 
drill such a hole through the web of a rail ^" thick in less than half a minute. 

The motor consists cf three reciprocating pistons, working in the same 
number of cylinders, and is of the latest design. It is very efficient, and strongly 
m.ade, and as will be noted, is rigged with power feed, operated by hand, requiring 
but little effort on the part of the operator to force the drill into the work. 




USE. 



BOLT CUTTING MACHINE. 



899 



Among the many interesting and novel appliances shown at the M. C. B. 
and M. M. Convention at Old Point Comfort, Va., in session from June 8th to 
i8th, was an "Acme Bolt-Cutter" fitted with "Fergusson's Pneumatic Turrets." 
(See cut.) This machine attracted a great deal of attention from the members 
of the Conventions on account of the novel use of compressed air, the operator 
having but to place the bolts in- the machine and the air did the rest, carrying the 
bolt into the threading dies, bringing it out when threaded and throwing the 




FIG. 350.— ACME BOLT CUTTER WITH PNEUMATIC TURRET. 



bolt from its position in the machine, leaving the space occupied by the bolt ready 
for the operator to put in another. These pneumatic turrets are designed to in- 
crease the rapidity with which bolts may be threaded, not by altering the speed 
of the die-heads, but by reducing the time taken to close the dies and remove 
and replace the bolts, their action being entirely automatic, each bolt being 
ejected and the blank started in the fraction of a second. 

In increasing the production of the machine nothing is lost in the quality 
of the product, as the air pressure while the bolt is threading is beneficial both 



900 



USE. 



to the dies and to the thread. The product of the machine is very large, as will 
be seen when we say that as many as 7,200 of ^-in. bolts have been threaded on 
it in nine hours with one operator. 

The makers' name is a guarantee of the quality of the machine, which is 
strictly first-class throughout. Any further information will doubtless be cheer- 
fully furnished by the makers, the Acme Machinery Co., Cleveland, Ohio. 



USE OF THE PNEUMATIC CLIPPING TOOL IN SHAPING REFRAC- 
TORY MATERIALS FOR FURNACE WORK. 

The cuts shown herewith illustrate the application of compressed air 
for shaping refractory materials for furnace work at the works of the American 
Gas Furnace Company, Elizabeth, N. J. The bricks warp while being burnt, and 
to make the surfaces and all joints accurate, and obviating an excess of fire clay 




FIG. 351. — CLIPPING FIRE BRICKS. 



at the joints, advantage is taken of the pneumatic chipping tool. Not only does 
this make an excellent surface, preventing the edges being broken off, as for 
instance when using a hammer and chisel, but holes can be bored accurately from 
markings made when outer steel "shields or casings are applied for furnace and 
muffle work. 



I 



USE. 



The air is delivered at 45 pounds pressure from a belt driven compressor. 
By means of an automatic arrangement only sufficient air is compressed to meet 
the demands of the chipping tools, thereby economizing the amount of power ab- 
sorbed. 

From actual tests a 1" hole six inches long can be bored in four minutes, 
and a ij^" bole six inches long in three minutes; cutting a groove \" x J4" deep 
and 12" long in two minutes. Plain surface work is done very rapid and effec- 




FIG. 352. — BORING FIRE CLAY. 

tually. These figures fully demonstrate the economy of the use of air for this pur- 
pose, and also for hoisting the material about to be worked upon. 



LOCOMOTIVE BELL RINGER. 



The cut herewith shows the Bartow Locomotive Bell Ringer which is 
operated by compressed air, and is now being marketed by the Chicago Pneumatic 
Tool Co. This has been in use for about two years on several railroads in the 
East, with the very best of success. 

The motor for ringing the bell has no direct connection whatever with the 
bell, the crank of the bell shaft having a roller which works over the disc shown 



902 



USE. 



on motor. The valve is operated from an arm, extending from the piston rod to 
the valve rod, and two adjustable nuts, one above a»d one below this arm, adjust 
the length of the stroke of valve. This also regulates th espeed at which the bell 
is rung. 

There are very few parts to this bell ringer, and in the two years' service 
they have been in, there have been no repairs. It is easily placed on the engine 
by a small bracket on the bell frame. The simplicity of the machine can be easily 
seen, also the economy in running it, the stroke being very short, and only i^ in. 




FIG. 353. — LOCOMOTIVE BELL RINGER. 

in diameter. It is operated by air from the main reservoir on the engine, and is 
rung from a valve placed in the cab. 

It has been shown that on an engine equipped with a bell ringer, the saving 
in consumption of fuel has been enough in one month to pay for the device. The 
explanation of this is that the fireman has so much more time to attend to the 
firing of the engine, instead of looking out of the window and watching for cross- 
ings to ring the bell. 

This little device is going to meet with favor among railroad men. 



AIR GUN. 

As a great deal of trouble has always been experienced in driving out engine 
frame bolts, cylinder and saddle bolts on locomotives, the use of a cannon many \ 
times being brought into play, the Pennsylvania Railroad system has adopted 
what is known as an air gun for doing this work. 



^V Fie 



USE. 



903. 



Fig. 354 shows a section of the gun as they make it. It is nothing but a piece 
of bored-out steel tubing screwed into a cap, which acts as a base. The size of 
the gun can be varied to suit different kinds of work, the diameter," length of 
piston and length of stroke being increased if more power is to be obtained. The 
three-way cock is attached to the air inlet so that after the air has shot up the 



FIG. 354 







FIG. 355. 

piston, the air in gun can escape to the atmosphere when the three-way cock i\ 
turned. 

Fig- 355 shows part of an engine frame with several of the air guns in place 
for driving out the bolts. The three-way cock on the air inlet is opened and 
closed, hitting the bolt with a sharp quick blow. As shown in cut. the gun 's 
blocked up intermittently, acting as a heavy hammer with wood to the required 
height for operating, which allows it to accommodate itself to many varieties of 
work. 



904 



USE. 



DROP PIT JACK. 

In the Chicago & Alton Railway roundhouse at Bloomington, 111., there is 
being installed a locomotive driving wheel drop pit which gives promise of 
being a most convenient institution. Its jack is not only operated vertically by 
compressed air, but is transferred from one pit to the other by means of a long 
horizontal cylinder, with a piston having rods extending through each cylinder 
head and engaging in either direction with lines of wire rope attached to the 
jack carriage. 

In Fig. 356 can be' seen a cross section of the pit, the center line of which is 
33 ft. 8 in. from the shop outer wall, toward which the engines are headed in this 
roundhouse. The shop floor is level with the lower edge of the rail head and the 
floor of the drop pit is 7 ft. 6 in. below this, while the sub-pit in which the jack 
runs is 3 ft. 6 ins. in depth below the level of the pit floor. The pit is 81 ins. 
in width between the walls, the sub-pit is 22 ins. in width, the longitudinal dimen- 




FIG. 356. — NEW DROP PIT AT BLOOMINGTON, C. & A. RY. 



sions of both pits are the same and are such as to connect both pits with a couple 
of feet free space beyond the outside rail of either track. The 8 x 10 ins. 
stringers which support the section of rails across the pit have their ends sup- 
ported by longitudinal stringers, in which illustration is also shown the hinge 
method by means of which the rails supporting stringers are swung around on 
top of the pit stringers and thus carry the pit section of the rails out of the way. 
In Fig. 357 are shown the details of the pneumatic pit jack and of the 
transfer carriage on which the jack is hung. The jack has a piston 15 ins. in 
diameter, with a vertical hoist of 4 ft. 6 ins., which enables it, as shown in Fig. i, 
to readily remove or replace any driving wheel with which the locomotives on 
this line are equipped. In Fig. 357 can be seen the details, and in Fig. 356 
the position of the horizontal cylinder which, by means of the movement of its 
piston, pulls the ropes which transfer the jack carriage in either direction. This 



USE. 



905 



cylinder lies alongside one of the pit track rail stringers, has a bore of 8 ins. and 
its piston travels 5 ft. The piston has a rod extending through the cylinder in 
either direction to the heads of which are attached a double block. Through this 
block and through two additional single blocks at the ends of the pit are rigged 
lengths of 3-8 in. wire rope, which connect to both ends of the jack carriage. 
By means of a suitable valve, air pressure is admitted to this cylinder for moving 
its piston in the required direction, and this in turn draws the jack carriage as 
desired. We believe the use of air for this transfer movement is novel, but 
whether or not this is the case, it certainly affords very convenient method of 



v^V- 




FIG. 357. — DETAILS OF PNEUMATIC APPARATUS. 

transferring the jack carriage, which, when laden with a pair of driving wheels 
to which are attached driving boxes and eccentrics with their straps, are a 
weight needing considerable effort at times to move. Further study of the illus- 
trations here presented will show any point of additional interest which the 
arrangement commented on here may occasion. — Railway and Engineering 
Review. 



PNEUMATIC HAND RAMMER. 

The pneumatic hand rammer, illustrated herewith, is designed to meet a 
large variety of work in the foundry, not only on the floor, but on heavier loam 
work, where it may be used to good advantage alone or as an auxiliary to the 
heavier type of pneumatic rammer which is suspended from a crane. This hand 
rammer is in general design similar to the suspension rammer, but is made light 



9o6 



USE. 



enough so that its use cannot become irksome to the operator. At the same 
time it is sufficiently heavy so that its inertia absorbs any variation that may 
arise from the rapid reciprocation of its piston and the rammer head. There are 
no exposed working parts to this machine, so that dust and dirt cannot affect its 
operation and durability. The valve mechanism is entirely inclosed, and is as 




FIG. 358. — PNEUMATIC SAND RAMMER. 

simple as is consistent with proper distribution of air in the cylinder and smooth 
working. The rammer rod is hexagon in shape, as shown in the engraving, so 
that it cannot turn except at the will of the user. It is also arranged so that the 
piston will remain at the top of its stroke when the machine is stopped. The 
weight of this rammer is 45 pounds, and it strikes 250 to 300 blows per minute, 



USE. 907 



r 

^^Tfsing air pressure at from 50 to 100 pounds per square inch. Only 15 cubic feet 
of free air per minute are consumed in continuous operation, as shown in the 
illustration. The machine is provided with a handle on each side; to the handle 
on the right side is attached the air supply holes and the admission of air to the 
cylinder of the rammer is controlled by means of a throttle lever under the thumb 
of the user ; exhaust air passes out through the handle on the opposite side ; the 
speed and force of the blows may be varied at the will of the user. A number 
of different shaped rammer heads are provided with each machine; they are 
attached to the rammer rod by means of a taper fit and may be changed in less 
than one-half minute without letting go of the handles. 

The manufactures of this machine, the Philadelphia Pneumatic Tool Co., 
of Philadelphia, New York and Boston, are furnishing these machines for a 
great variety of uses. Besides regular foundry work, it has been found to be 
unsurpassed as a labor saver in ramming up converter bottoms in Bessemer steel 
plants, and the rammers have been adopted by a great many of the largest plants 
of this kind in the country. The rammer has also been found useful in ramming 
the moulds of special shapes of fire brick for use in glass and other furnaces. On 
any kind of work where ramming has to be done, it is safe to say that this ma- 
chine in the hands of an unskilled workman will do the work of from four to 
six men using the ordinary ramming bar. 



THE YEAKLEY VACUUM POWER HAMMER. 

The Yeakley Vacuum Hammer Company, of 3 Rochester Row, West- 
minster, have installed at the works of Messrs. John Mowlem & Co., the con- 
tractors of Westminster, one of their new vacuum hammers, the working of 
which we recently inspected. In this hammer a vacuum is used to stop or control 
a falling weight. As it has been designed to do light and heavy forging in iron 
and steel without any variation of speed, the hammer head or ram is actuated 
by vacuum and pressure and controlled by a simple valve mechanism that responds 
to the slightest touch, being so sensitive that the pressure of a finger on the 
treadle is sufficient to operate it. It is lifted by vacuum and driven down by air 
pressure. When the hammer is put in motion, the head or ram lifts up and 
carries perfectly still at the highest point of its range. It is held there by the 
vacuum, the air pressure being cut off by the valve. The balance wheels, pitman 
and piston are running, and the head is at rest. To make it strike, the valve 
is opened by operating the treadle, and the air pressure is admitted to the ram 
to drive it down. The instant the valve is closed by removing the foot from the 
treadle the ram remains up, or lifts up if the valve is closed when the head is 
down. As it can always be depended upon for one blow, it is available for drop 
forging. The hammer head acts both as ram and piston in front cylinder. 

The principal points claimed for this hammer are that it strikes a light 
or heavy blow, at will of the operator, the regulation being obtained by the 
treadle, and gives a dead blow with pressure following clear down, thus pre- 
venting work moving about on the anvil. There is, of course, no piston rod to 



n 



908 USE. 

break, and no springs, helves, or rubber cushions to get out of order. The 
movement of the treadle is adjustable from i to 3 inches, and when the work 
is not too large, the operator can manage both work and hammer perfectly. The 
foundation is very simple and inexpensive. 

The rams are guided on all four sides and have large die surfaces on all 
sides. This allows several dies or swedges to be placed on the ram together, 
and each can be used continuously, so as to do several operations in succession 
at one heat. In fact, this hammer has many of the features of a drop hammer. 
The large die surface and accuracy are suited to such work as has been done 
in board drops. The Yeakley hammer action is such that the ram comes down 
quicker than a drop hammer, but hangs an instant at the end of the stroke with 
full pressure so as to kill the spring of the metal, so that it does not rebound 
to the same extent as a drop hammer. 

The rams vary from 36 lbs. to 800 lbs. in weight. The weight of the ram 
can be varied without interfering with the frame. In the latest built the 150-lb. 
ram weighed 162 lbs. and the 400-lb. ram weighed 480 lbs. 

In the smallest sizes the anvil is united with the main frame. In all 
others it is separated. The head or ram is represented as down, but it lifts 
instantly when the belt is thrown on the pulley and will strike the moment the 
treadle is depressed. — Iron and Coal Trade Review. 



AN INERTIA VALVE PERCUSSIVE TOOL.* 

In the last few years the use of compressed air as a motive power for ma- 
chinery has wonderfully increased, especially for portable tools. This is mainly 
due to the advantageous qualities of compressed air over steam, the principal of 
which are : 

First. Stability, or in other words, non-condensation, permitting it to be 
stored indefinitely, or to be transported long distances without loss of pressure, 
other than that due to leakage and friction of the conduit. 

Second. Low temperature at which it can be used in hand tools. Such 
tools could be run by steam, but they would become so hot that a man could not 
hold them in the naked hand. 

Third. The exhaust consists of fresh cool air, adding to the ventilation 
and comfort of the workroom or mine, whereas the exhaust from steam motors 
has to be disposed of outside, and is a nuisance, and with hydraulic systems, the 
waste water must be carried away in pipes. 

Fourth. It can be used at any pressure and is easily produced, and its 
expansive qualities, while not on a par with steam, owing to the absence of heat, | 
yet can be utilized with good results, a feature entirely absent in hydraulic 
systems. 

Against these advantages are opposed some few disadvantages, such as 
the losses of power in the compression of air, due to the absorption of energy in 
the generation of heat, and the subsequent loss of pressure in the compressed 
* Paper read before the Engineers' Society of Western Pennsylvania. 




USE. 909 

air, as it cools down to the temperature of the surrounding atmosphere. The 
losses of the steam end of the compressor are similar to those of any steam 
engine, and are well known to all of you. 

The absorption of heat from surrounding media, caused by the sudden 
expansion of compressed air, often to such an extent as to freeze any moisture 
in the air or immediate neighborhood, will often prevent the use of high pres- 
sure air expaifsively unless the air be reheated. This reheating of compressed 
air can be done at very small fuel cost for the benefits attained, and is used 
in many places. 

These points, however, are well understood and compressed air is used 
intelligently. 

With these few reminders of the qualities of compressed air, the subject 
of its application 'to percussive tools comes up, which can be better understood 
by prefacing with an outline of the development of percussive engines of different 
types, followed by a description of the inertia valve type which is the subject of 
this paper, and a discussion of some of the theoretical and engineering features 
involved in its design. 

Percussive force, as regards the actual work done upon the object struck, 
is applied in two ways : 

First. Directly, when the tool itself is propelled through space and strikes 
the object, when practically all of the energy of the moving mass is expended 
on the object struck. The commonest examples are the hand hammer, sledge, 
steam hammers, rock drills, mining stamps and others of similar character. 

Second. Indirectly, when the moving mass strikes an interposed tool, 
through which the energy is transferred to the object. 

In this case a portion of the energy is consumed in overcoming the inertia 
of the interposed tool; the remainder only performing useful work on the object. 
The energy thus consumed in overcoming the inertia of the interposed tool, sup- 
posing the energy of percussive force to be constant, varies, by well known laws, 
according to the weight or mass of the interposed body. The mathematical dis- 
cussion of inertia is out of place in this paper, but those interested in the subject 
can find full discussion of it in Weisbach's, Rankine's and other works on ap- 
plied mechanics. 

Examples of this second type of application of percussive force are the 
mason striking his stationary chisel, the quarryman's drill struck by the sledge, 
and the chisel struck by the piston of a pneumatic hammer. 

After hand hammers, which have been used from time immemorial, per- 
haps the lifting of a weight and subsequent dropping it, was the first step in 
advance, and one which is still in daily use in drilling oil wells and driving piles. 

Trip hammers of crude form were in use as early as 1600, and before 
them, spring catapults were used to throw great stones against castle walls. In 
a manner these may be classed as hammers of the first type, as the projectile 
certainly struck a blow, as do those of our great modern rifles, with a little more 
force. 

Nasmyth's steam hammer, invented in the early forties, was a great step 
forward, and undoubtedly led to the invention of the rock drill, although as far 



9IO USE. 



1 



back as 1683 a drill of the oil well type was used for rock, but only vertical 
holes could be drilled. 

In 1844 one Brunton suggested compressed air in a cylinder as a con- 
venient means of working a hammer to hit a drill, and in 1859 Nasmyth, who 
was a wonderful engineer, at a meeting of the British Association for the Ad- 
vancement of Science, suggested that the loss of energy in overcoming the 
inertia of an interposed tool could be overcome by lancing or projecting the 
tool itself against the work, and exhibited a sketch of an ingenious machine 
having a piston with a tool attached to the piston rod, working in a cylinder, 
closed at the lower end and open at the top, so arranged that when the piston 
was mechanically pulled to the back of the cylinder, a vacuum would be created 
below it, and on releasing the piston the atmospheric pressure would drive it 
down with a constantly increasing velocity. This device, he pointed out, could 
be used to drill holes at any angle, as it was independent of gravity for its 
power. 

October 15, 185 1, Cave, a Frenchman, patented a machine for rock drilling, 
run by compressed air, in which the valve was actuated by hand, and the drill 
rotated by hand. It was a double-acting engine and was successfully used, and 
was the pioneer rock drill in Europe. 

Couch, an American, patented a rock drill in 1849 in which both the valve 
motion and the rotation of the drill were automatically performed by the piston 
in its motion, and while it was a cumbersome machine, requiring cranes to 
handle it, it was in its essential features the rock drill of to-day. 

Since that time there have been wonderful improvements in detail, and 
numberless devices made for regulating and controlling the different parts, yet 
to America belongs the credit of the real development of the rock drill. 

There are three methods of automatically controlling the admission of 
motive fluid in rock drills and other percussive engines. 

First. The tappet valve type, in which projections attached to the recipro- 
cating part, strike triggers or other devices which in turn move the valve. 

There are several objections to this type. The clearances are necessarily 
large, the liability to breakage is great, due to the intricacy and multiplicity of 
parts ; the small variation of stroke permittable, and the fact that the valve must 
be moved before the piston has completed its stroke. 

This is a good feature on the back stroke, as it permits of forming a sure 
cushion preventing piston hitting back cylinder head, but on the front stroke it 
is bad, as it allows initial pressure air to bear against and partially check the 
velocity of the piston, hence weakening the possible blow. 

Owing to the skill and care with which machines of this type are con- 
structed, most excellent results have been and are now being accomplished with 
them, and such well-known manufacturers as the Ingersoll-Sergeant and the 
Rand Drill Companies, continue to sell them in large quaitities. 

Second. The fluid moved valve type, wherein the piston itself, at certain 
parts of Its travel, admits a supply of motive fluid to move the valve or to move 
a supplementary piston which in turn moves the valve. 



I 



USE. 



91 



Such machines, if well made, are not liable to get out of order, but the 
stroke is subject to limitation within narrow range of length, and air is admitted 
before end of out stroke, as was described of the tappet valve type. 

In neither type has there been much attempt to use the air expansively, as 
the decreased velocity due to decreasing pressure, and the additional mechanical 
complications, did not seem to warrant it. 

The Optimus Drill, of English make, is an exception. It belongs to the 
fluid-moved valve type, using the motive fluid compound. The initial fluid 




FIG. 359. — DARLINGTON VALVELESS HAM] 



912 USE. 

driving the piston outward, is used expansively to effect the return stroke. It is 
much in use abroad, but has not met with much favor here. 

Third. The so-called valveless type, in which the moving piston acts as 
its own valve, as in its stroke, it alternately opens and closes certain ports, so 
that the fluid acts on each end of the piston in turn. 

The progenitor of this type was invented by John Darlington, May 13th, 
1873, in England, and a great many were used, though now superseded by the 
modern drills of the first and second types described. 

In this machine, the motive fluid acts constantly on the smaller area of 
the piston. When the piston is at the outer end of its stroke, the space in the 
rear is open to the atmosphere and the constant pressure on front area forces 
the piston back. In its motion, it closes the exhaust port and a back cushion is 
started in the rear. At a certain distance before the motion of piston is entirely 
checked by the cushion, a by-pass leading from front to rear end of cylinder, is 
opened; this by-pass being a little longer than the main body of piston. Fluid 
rushes through this passage to the space in rear of piston, pressing on large dia- 
meter of same with initial pressure, drives piston forward against the pres- 
sure on small diameter, with a force due to the excess of area, under the same 
pressure per square inch. Very early in the down stroke, the by-pass is closed 
again by body of piston, and further force is derived only from the expansion of 
the body of high pressure fluid, locked in the rear of piston. 

Against this decreasing pressure of expansion is opposed the constant 
pressure on the small front area, so that the net forward force is constantly de- 
creasing, although sufficient, combined with the momentum already acquired, to 
propel piston its entire stroke with considerable velocity, utilized in effective 
work on the object struck by the tool. When nearly at end of out stroke, the 
exhaust in rear is again opened, so that further travel is entirely due to the 
acquired momentum. As soon as the blow is struck, the piston is stopped, and 
immediately is pushed back by pressure on front area and the operation repeats. 

The conception is unique and beautiful, the drawback being the loss of 
velocity on the out stroke, as described. 

The action of this tool has been explained in detail, at is was in the 
endeavor to overcome this defect that experiments and study were made of the 
problem. 

In Darlington's drill, the initial pressure was used for the back stroke, 
and the expansive force used for the out stroke. April 13th, 1880, Wm. L. Neill 
took out a U. S. patent for a valveless rock drill, reversing this action, so that 
the effective out stroke was due to initial pressure, and the return stroke to 
expansion. This device never was used practically, as far as can be ascer- 
tained, probably due to the fact that a cushion was formed in front of the piston, 
when the exhaust was closed, increasing in force as the piston progressed, and 
decreasing the velocity thereof. 

Having thus examined the three principal types of valve motion in ordinary 
use, we come to the development of the Pneumatic Hammer, which consists 
essentially of a small portable cylinder in which a piston reciprocates very rapidly, 
striking a great number of blows per minute on the end of a tool inserted in 
the end of the cylinder. 



i 



USE. 



913 



It belongs to the second class of percussive tools, having a tool interposed 
between the hammer and the work. 

McCoy may be said to be fairly entitled to the credit of the first applica- 
tion of such tools to heavy work, such as chipping metals, caulking boilers, cut- 
ting stone, etc., that had been done previously by hand and hammer. He exhi- 
bited his device before the Franklin Institute, which awarded him a medal for 
a new and meritorious invention of real utility. 

He was not, however, the originator of the broad idea, as long before he 
perfected the tool for heavy work it had been used as a dental plugger, a device 
working compressed air in a cylinder so that a piston struck the end of a tamp- 
ing tool, used to insert gold into the cavities of teeth. 

There were several patents taken out for such tools and successful results 
attained in the 70's. 

The pneumatic hammers followed in a general way, the valve motions 
used in rock drills, with modifications adapted to smaller and more portable 
tools. The valveless, as also tappet and fluid moved valve, types are used. Of 
the former, the Q. & C. tools are quite well known. . For work within their 
range they are admirable, owing to their simplicity of design, small size and 
great rapidity of short stroke blows. For light chipping, caulking and other 

AdmHtance Pori^A- 

AreaE- 




OuicfeJ' 



AreaE' 



•Exhausf P(pH 



FIG. 360. — KOLTEN TOOL. 



similar work they can hardly be excelled. A somewhat similar tool, the Kotten, 
is made for use in carving stone and marble, die sinking and other delicate work, 
and has a very short stroke, about %" to J^", running as high as 10,000 or more 
strokes per minute. 

For heavy chipping, riveting and other work, the blow of a valveless tool 
is not heavy enough to do the work well, and tools with a controlling valve are 
used, allowing of much longer stroke, and higher velocities of piston travel. 

Of the fluid-moved valve type, the Boyer hammer, made by the Chicago 
Pneumatic Tool Co., and the Little Giant hammer, made by the Standard Pneu- 
matic Tool Co., are the best known. In these a small valve, located in a cham- 
ber in the rear of the piston, traveling parallel or right angles to the axis of the 
piston, is actuated by air pressing on differential areas, moving it alternately to 
and fro, opening and closing ports controlling the admission and exhaust to the 
cylinder. Suitably placed small ports are closed and opened by the piston in 
its travel, that permit air to act on and move this valve. 

Excellent work is accomplished by these tools, and a skilled workman can 
do from four to six times as much as can be done by hand tools alone. They 
are in use in nearly all the progressive machine, boiler, bridge and ship works 
in this country, and in a grjeat many abroad. 



914 



USE. 



In driving rivets greater force is required than in chipping. This can be 
attained in a pneumatic hammer in two v^^ays : By larger mass in the piston, or 
by greater velocity. 

The force of the blowr varies directly as the mass or weight; and as the 
square of the velocity; hence a tool can be designed with a heavy piston and 
short stroke with high pressure, or the same result attained by larger cylinder 
diameter with lower pressure, but the better, and generally adopted method, is 
to increase the length of stroke, keeping the diameter small. This would follow 
thoretically as a result of the law given. There is again a practical reason why 
the diameter should be kept small, because the reaction would otherwise be too 
great. Since action and re-action are equal and in opposite directions, the total 
force used to propel the piston out, presses equally against the back cylinder 
head, and a man can withstand but a limited amount of such pressure when 
holding the tool, thus limiting the diameter to such size as has been found 
practicable. 

To meet the demand for a long stroke tool, the Chicago Pneumatic Tool 
Co. have put on the market the "Long Stroke Boyer Hammer" having a piston 
about i^-in. diameter, with 9-in. stroke, striking a very hard blow, due to the 
continued application of a constant force through the long stroke, constantly 

^'Admiti-ance Poti „ „ 




FIG. 361. — LONG STROKE BOYER HAMMER. 



accelerating the piston velocity. The valve is moved by tappets and at pressures 
of about 100 lbs. per square inch. Seven-eighths-in. rivets can be set down much 
quicker and about as tight as by hand, but the rivets do not fill the holes as well 
as those driven by compression riveters, driven by air, steam or hydraulic pres- 
sure, nor nearly so quickly. For the erection of structural work, or for any field 
riveting, it fills a long felt want, doing the work sufficiently well. 

With this perhaps rather long examination of what has been accomplished 
in percussive tools, and study of the underlying principles, the subject of this 
paper, "An Inertia Valve Percussive Tool," will be discussed. 

Recalling the Darlington Valveless Rock Drill and referring to the draw- 
ing (Fig. 359), we notice that when the rear edge F of the piston passes exhaust 
port D on the back stroke, that a cushion is at once started in the rear, increas- 
ing in pressure as the piston travels back. When the front edge A of the piston 
passes and opens the entrance B of the by-pass B-C, initial pressure air flows 
through admittance port M, cylinder cavity and the by-pass to the rear of the 
piston, immediately checking any further movement and forcing the piston out 
by reason of the greater area of surface F over surface A. In such forward 
movement the edge A again closes the port B of by-pass, cutting off the supply 
of further initial pressure air to the rear, so that any additional pressure or force 
upon rear area of the piston must be derived from the expansive action of the 



r 



USE. 915 



air locked in behind it, which, you will notice, is opposed by the initial pressure 
air bearing on surface A, which is constant at all points of stroke, either for- 
ward or back. 

It seemed, on study of this device, that if some way could be found to 
allow air of initial pressure to follow up the piston during its entire downward 
stroke, that much greater piston velocity would be secured. 

To accomplish this result, it was obvious that an automatically moved 
valve of some sort must control the flow of air in such a way as to prevent any 
access to the rear during the back stroke, and to permit such access during the 
forward stroke. 

The first solution that appeared was the use of a type of poppet valve, 
with a spring bearing upon it, so that when there was no pressure on one side, 
the valve would close under unbalanced pressure, but when the pressure was 
alike on each side, the spring would force it open. 

To clearly understand it, referring to the print A is a port admitting air 
continually against area E. G is a port leading from this area E to the valve 
chamber shown. 

C is a valve with spring D bearing against the side of it that is away from 
the constant supply of initial pressure in port G, arranged so that pressure 
against it from port G will close it against pressure of spring, when no pressure 
exists back of it. 

B is a by-pass having two outlets communicating with cylinder h & h'. F 
is an exhaust port, adapted to be closed and opened by the rear edge of the pis- 
ton. J is a guide to prevent piston from turning, as the device as shown re- 
quired that the valve cavity should not come in contact with the exhaust port F. 

In action, air enters through A, pressing against small area E closes 
valve G and forces the piston back, the space in the rear of piston and in the 
by-pass and valve cavity having exhausted through port F. 

When the piston travels so that the edge E passes port B, air at high 
pressure goes through by-pass to rear, and at the same time through the port h 
into the valve cavity, thus equalizing the pressure on the sides of valve C, which 
opens under the pressure of the spring D, permitting free passage of the air 
through port E, and the valve cavity port h and by-pass to the hear, forcing 
the piston out, owing to the excess area. 

As it travels out, this passage, either through B or h is continually open, 
so that a continuous current of air flows through the valve at initial pressure 
until the exhaust port is opened at F, reducing the pressure in the rear when the 
valve again closes, and the action is repeated as described. 

This seemed very nice on paper and worked fair to middling badly. When 
the spring C was exactly right in intensity for a given air pressure, it worked 
nicely, but any variation of pressure interfered with good results. Again, the 
rush of air through the valve had a strong tendency to close it, requiring a super- 
fine adjustment of the intensity of the spring. 

For static pressures the idea was all right, but for dynamic pressures, if 
one could so call air under pressure in motion, it was not all that could have 
been desired. 



9i6 



USE. 



FIG. 362. 

In the line of simplicity and experiment, a rearrangement of the parts 
was made, as shown in drawing. 

The poppet valve was placed in the axis of the piston, which did not then 
require guides to keep it from turning and the construction was simpler. Results 



r 



USE. 917 



somewhat better than in the first machine were attained, but it was discovered 
that the inertia of the poppet valve interfered with the contemplated action of 
the device. 

This movement of the valve by inertia suggested the use of a form of 
slide valve that should be controlled entirely by inertia, opening and closing 
suitable ports in its travel to accomplish the desired ends. 

A tool as shown, in the drawing was designed, having an axial hole in the 
centre, within which a small tube could move freely within fixed limits. 

A constant supply of air is admitted at 4 against the small area of piston. 
Ports 5-5 lead from a point adjacent to this small area into valve chamber, 
which in turn opens to the rear end of piston. . 

An exhaust port, 14, leads through the cylinder and a groove around 
exterior of piston communicates by a port 7 to the valve chamber. 

In starting, the tubular valve is at the outer end of chamber, thus closing 
ports 5-5 and leaving ports y-^ open. 

Owing to the constant pressure on the small area, and the exhaustion of 
pressure in rear of piston, it travels back, and the rear edge closes exhaust port 
14, which, however, registers at the same instant with annular groove on piston, 
establishing a new means of exhaust through the valve chamber, ports 'j-'j and 
annular groove 8 to port 14. This passage remains open until the groove 8 
passes exhaust port 14 and the piston cuts off further exhaust. A cushion then 
commences which tends to check the velocity attained by the piston, but not 
that of the valve carried thereby and traveling with equal velocity. Being free 
to move, the valve slides back until it meets stop 9. 

In this position the interior exhaust ports y-y are closed, and the admit- 
tance ports 5-5 are opened, and initial pressure air flows through the valve to 
the space in rear, driving piston out by reason of the excess area. 

The valve remains in this back position, allowing air to flow through it 
until the piston has struck its blow, when the valve slides, by reason of its 
inertia, to its outer position, and the action repeats as described. 

It will be noticed that full pressure is exerted until after the piston has 
struck, and also that the valve will shift at any point during the out stroke if the 
piston is stopped, provided that exhaust can occur. The possible limit of prac- 
ticable variation of stroke is thus only limited by the distance found necessary 
to use for a rear cushion to prevent piston from ever striking the back cylinder 
head. 

This varies from J4 to 1-3 of the stroke length, thus permitting a wonder- 
ful variability of stroke. 

The tool, as described, worked very well at times, but it was discovered 
that the valve had a strong tendency to bounce back, especially on the front 
stroke. This unlooked for movement of the valve had very disastrous effects, 
as may be imagined, causing the action to be extremely erratic. 

To obviate this trouble, brakes were applied to the valve to prevent its 
sliding so easily. The machine ran well when it got a good start, but the valve 
was liable to stick at the wrong end of the chamber, and there was great difficulty 
in starting again until the piston had been jarred by hand so as to bring the valve 
where it should have been. 




9i8 USE. 

Other experiments, such as the use of rubber, lead, wood and other buffers, 
supposed to be inelastic, were tried in the endeavor to stop the bounce, with but 
little success, as anything soft enough to prevent bouncing was soon hammered 
out of all shape, the pieces clogging up the valve chamber. 

All sorts of shifts, profoundly wise and exceedingly foolish, met the same 
fate, until we were almost disheartened and disgusted with the perversity of 
things inanimate. 

In pondering over the failure, the idea of counter-balancing the rebound 
of the valve by a smaller mass, colliding it with it at the instant rebound com- 
menced, arose. 

A little model consisting of a pipe, with two collars fastened to it having 
between them another piece of pipe large enough to slip freely on the outside of 
the other, and a little less in length than the distance between the collars, was 
made. 

On holding this device about three or four feet above a block of steel, 
with the outer tube or "Rider" as it was named bearing against the upper collar, 
it was dropped vertically. The lower end of the inner tube struck first and 
started to rebound, but the rider, traveling at the velocity due to the fall, slipped 
over the main tube until it struck the lower collar, fast on inner tube, thereby 



I . 

"•■■Rider orjjjose Sleeve 
i ^-R'HjicI Surface 

FIG. 363. 

checking the upward velocity of the rebounding inner tube, so that the combina- 
tion practically did not rise perceptibly from the steel block, landing almost as 
dead as a chunk of putty. 

It seemed as if this principle could be applied to the valve, so as to over- 
come its rebound, and at the same time give the freedom of motion necessary to 
good action. 

A modification of the valve was made with a rider attachment, which, 
when tried, caused the tool to work with the regularity of clock work. 

In designing the valve and rider, a study was made of the coefficients of 
rebound of various materials, and it was found that a great deal of difference in 
results and theory existed among the acknowledged authorities on applied me- 
chanics, authors of distinction, such as Rankine, Weisbach and others giving 
tables with wide variations for similar materials. 

In order to be sure, recourse was had to experiment with different ma- 
terials, to determine what proportionate weights the valve and rider should have 
to each other. 

It has been demonstrated by mathematicians that the modulus of elasticity 
of rebound is equal to the ratio of the relative bodies after and before impact. 

If a body suspended from a small cord from a fixed point be made to 
oscillate like a pendulum, it will acquire a velocity, at its lowest point, propor- 

\ 



r 



USE. 



919 



tional to the chord of the arc through which it has swung, and if the arcs are 
not very long, the times of descent will be equal for different length arcs ; hence, 
if the suspended body strike a stationary body when at its lowest point, and the 
angular distance through which it rebounds be noted, the ratio of the original to 
the return velocity can be determined. 

It was found that for steel striking steel, it was as 100 to 60, and for steel 
striking vulcanized rubber, backed by steel, about 100 to ^yj. The fibre was used, 
as it stands the pounding of the valve without itself disintegrating, or upsetting 
end of valve. 

Knowing, then, the modulus of recoil we can figure the velocity a body 
will acquire at the instant after collision on the rebound, if we know the velocity 
with which it struck. 

If, in addition, we know the weight of the striking mass we can find the 
energy or momentum at that instant, and have only to make the weight of rider 




«OCHO«t) o» 14.' TRftVLL 
(B'r>iono 10 P01HI or ntBOimo 
«-B- <B -- 100 bO 

fc« STiti ON bTei 



FIG. 364. 



such that its momentum, due to the initial velocity, shall be equal to that of the 
valve rebounding, to practically eliminate the return movement of the valve. 
When two perfectly elastic bodies of equal weight meet, each rebounds with 
substantially the same velocity with which they met, but with imperfectly elastic 
bodies, of unequal masses and velocities, the rebound depends on which has 
the greater weight and velocity, and on the moduli of recoil, hence we can 
approximately calculate the weight of rider so that the valve will stop short, and 
any rebound will occur in the rider only. This rebound can be made so little 
that it does not influence the valve inself, and the desired result is attained. 

In making these investigations, certain interesting points came up that 
are worthy of further study to fully understand the reasons for them. 



920 USE. 

The recoil certainly depends upon the elasticity of the colliding bodies, yet 
the ratios found by experiment seem to bear no recognizable relation to the 
established coefficients of elasticity, given in text-books on the strength of ma- 
terials. Evidently the amount of energy in the moving masses and the area of 
contact influence the result. If the striking area is small, the entire energy, 
converted into work, is exerted on a small unit of surface, causing a strain per 
unit area greater than the materials would stand. In this case the limit of 
elasticity, as ordinarily understood, might be exceeded when the work would be 
expended on tearing or crushing the material, instead of causing rebound. 

On the other hand, if a body of equal weight and velocity to the one 
described, but having a much larger striking area, were to collide, it might easily 
be conceived that the strain per unit of striking area would be less than the 
limit of elasticity of the materials, and that practically most of such energy 
would be consumed in bending or squeezing the materials, which would spring 
back to their original position, and in so doing force the colliding body back into 
space with a velocity dependent upon the strain produced and the coefficients of 
elasticity of the bodies. 

To elucidate the truth of this hypothesis would require a great deal of 
careful experiment and research, and would be suitable work for some me- 
chanical laboratory connected with a technical school. Accurate information on 
the subject would be of great value. It might originate a new method of testing 
materials, although somewhat analogous to impact testing that is now in vogue, 
although the results in the latter system are derived from measurements of bends 
made transversely in the specimen struck. By this method, such results would 
probably be derived from a comparison with the velocities of rebound from stand- 
ard substances, of bodies of given form and with given velocity. 

The latest model of a direct acting chipping tool is shown in the accom- 
panying sketch. You will note that the valve will move at any point of the 
stroke, if the velocity of piston be checked, and that within the limits for cushion 
described earlier in this paper, the stroke is variable. 

While this variability of stroke is not so essential in a chipping hammer, 
or any tool of the second class of percussion where an interposed tool receives 
the blow, yet for machines of the first class, such as rock drills, steam hammers, 
gold mine stamps, etc., such variability is desirable and essential to attain the 
best results. 

In this hammer the exhaust takes place at very nearly the initial pressure, 
hence a great deal of energy contained in the compressed air is wasted, although 
the piston velocity on the down stroke is great, giving a powerful blow. 

It seemed as if some of this waste might be obviated by working the air 
compound, using a different form of inertia valve so as to retain the good 
features of the device. 

It was evident that a constant supply of initial pressure air should be fur- 
nished, available at any point of the stroke, but that it should have access to one 
end of the piston at certain specified times only, and that the valve should permit 
of opening a passage from this side of piston to the other, which necessarily 
should be of larger area to allow of the locked in charge of high pressure air 
acting expansively on both piston areas. 



USE. 



921 



It was also a condition that during the movement of the piston under 
litial pressure that the other end of the cylinder should be open to exhaust in 




FIG. 365. 



such a way that variability of stroke would result, and sufficient cushion formed 
to prevent piston striking cylinder head. 

These conditions were fulfilled in a machine of the type shown in the 
illustration. 



92^ USE. 

An annular groove was provided on a portion of the exterior of the piston 
that was in register at all points of the stroke with an admission port of high 
pressure air. An axial valve chamber was provided, open at the rear end in 
the body of the piston, having from it ports leading to the constant supply of 
motive fluid; other ports leading to a point adjacent to the small diameter of 
the piston and exhaust ports, arranged so that exhaustion could occur through 
them during the majority of the back stroke, but be closed by the motion of the 
piston for the remainder of the stroke. 

A tubular valve was placed in this central chamber, having on its exterior 
surface an annular groove, so placed that when the valve was at the outer end 
of its travel, it would register with the ports from the constant source of supply, 
and the ports leading to smaller piston area, while at the same time a port 
through it would permit of exhaustion. 

In action, the pressure against the small area of piston drives it back, air 
in the rear meanwhile having a free vent through the exhaust ports until the 
piston, in its travel, cuts off exterior exhaust port, thus cushioning the air remain- 
ing back of the piston and checking velocity of the piston when the valve moves 
by its inertia to the rear end of its travel. 

In this back position the supply of high pressure air is cut ofif, as is also 
the exhaust port, and a port in the valve itself registers with the port leading 
to the small piston area, permitting the air locked in in front of the piston, free 
passage to the rear. The pressure immediately tends to equalize on both ends 
of piston, and owing to the larger area in the rear, the piston is forced out 
under the force of the expanding air from the front end of cylinder, continually 
decreasing in pressure as the piston moves, and the volume or space increases. 
The piston striking causes the valve to shift back to its original position, and the 
action continues. 

It is obvious that if the piston were back when at rest there would be no 
locked-up air to expand, so that it could not start, and to overcome this diffi- 
culty, a spring is placed back of the piston just strong enough to force it out 
when no air is admitted. No loss of power results, as the energy stored up in 
it on the back stroke is given out on the front stroke, and it serves to help 
cushion. 

The valve also is provided with a light spring sufficient to keep it in the 
outer end of its travel when the piston is at rest, so that all will be in readiness 
to start on opening throttle valve. The inertia of the valve on the down stroke 
is sufficient, when the piston is constantly accelerating in velocity, to prevent this 
spring closing the valve prematurely. 

The proportion of expansion can be determined if the clearances are 
known, for any ratio of piston area. It has been found that for air the propor- 
tion of 10 to 3 is good, as this gives a terminal exhaust pressure of about 2 
pounds per square inch if 8o lbs. were the initial pressure. This permits of 
prompt exhaustion, and no vacuum is formed in the rear, as would be the case 
if greater ratio of expansion were adopted. Such a ratio could be used with 
steam, as a condenser might be attached, but no experiments have been made in 
that line. 



USE. 



^^3 



FIG. 366. 



With this tool, about three times as much work can be done with the same 
vo^l^e of air as with a direct acting tool, exhausting at initial pressure, or the 
same work can be done with one-third of the volume of air. It may be seen that 



924 USE. 

the diameters of the tool might have to be larger to effect these results, and 
that the mass of piston would be larger in consequence. In practice, a longer 
stroke has been adopted in order to avoid the back kick, due to large diameters, 
as explained earlier. The length of stroke does not affect the ratio of expan- 
sion, as the volumes in front and rear of piston change in definite proportion. 

The velocities attained in forward and back strokes in either the com- 
pound or single acting hammers, can be calculated with fair accuracy when the 
diameters, piston areas, pressure per square inch, length of stroke and weight 
of piston are known, as these are constants or known variables. The amount of 
friction, leakage and loss due to overcoming inertia are difficult to determine 
exactly. 

Knowing the velocities and the volumes of motive fluid used, the number 
of strokes per minute and the amount of air consumption, can be closely approxi- 
mated, and in practice count of the number of strokes and accurate measurement 
of air consumption by meter, check out within from five to ten per cent, of the 
theoretical results figured. 

Thus a total can be intelligently designed to do the work expected of it, 
as regards force of blow, frequency of stroke, and air consumption at any given 
pressure. 

This valve motion would seem to be applicable to a great variety of pur- 
poses, even to running a compound engine with tolerable economy. The power 
of the stroke due to expansion is not 5 per cent, less than that due to initial 
pressure, on the small area, and a machine can be designed to strike by either 
initial pressure or expansive pressure, as desired. The latter has been chosen 
as giving simpler construction in the tool. 

The valve motion described and the anti-bouncer arrangement are covered 
by several patents, as is the poppet valve tool described.^ 

The tools, as now made, run very satisfactorily on long and severe tests, 
and are practicable and useful. 

Endurance tests of materials and detail parts are now being made with the 
view of discovering all weak points. 

When these have resulted satisfactorily, the tools will be put on the 
market. 

Owing to the great number of strokes and the small cylinder volumes in 
the tools already experimented with, it has been impossible to make indicator 
tests, so a study of the action of tools was only possible by observation of action, 
air consumption and number of strokes per minute, as the valve itself could not 
be seen at work. It followed that by induction only could one arrive at the 
causes of some of the erratic performances and failures of the tools. 

Chester B. Albree. 



CASKEY PORTABLE HYDRO PNEUMATIC RIVETER. 

The engraving shows a sectional view of a new style portable riveter man- 
ufactured by Pedrick & Ayer, Philadelphia, Pa., especially adapted for ship yards 
and structural iron works, and the use of boiler makers and bridge builders. 



USE. 



925 



The Caskey Portable Hydro Pneumatic Riveter is designed for using com- 
pressed air as a prime mover, with the hydro-carbon fluid used in the oil cham- 
bers and oil cylinders. 

This admits of the machine being operated in very cold weather and in 
open places v/ith no liability of freezing and causing trouble, as is the case with 
riveters of hydraulic construction, and is an important feature. 

The engraving is largely self-explanatory. The main frame, No. 68, is a 
steel casting, and can be made in any desired shape, adapted to the conditions and 
positions in which the riveter is to work. 

The oil chamber and pressure cylinder, No. 41, is made from nickel steel 
forging and accurately machined. 

The dolly bar or hydraulic piston. No. 13, is manufactured of the best tool 




FIG. 367, — CASKEY RIVETER. 



Steel, accurately machined, hardened and ground. No. 42, inside cylinder head, is 
of cast steel. ^ 

The Caskey Hydro Pneumatic Riveter is built for very hard usage, and the 
least liability of breakage. There are but four moving parts, and the operating 
lever. No. 15, is the only moving part exposed. 

All packings are easy of examination. 

The construction of the machine secures the maximum pressure on a rivet 
with as little weight in the machine as is possible. 

It works rapidly, without shock or jar, is easy to handle and gives a uni- 
form pressure on every rivet. 

No blow is given when using this machine and therefore no crystallization 
takes place upon the rivet when being driven. 

The riveter is suspended by a bale which allows it to be moved and operated 
in either a vertical or horizontal position; by changing the bale it can be used 
sideways with equal facility. 

Suitable handles are provided on front and back for the convenience of the 
operator in placing it over the work. 

The operating lever is so constructed and connected that the operator can 
control all movements of the riveter whether standing at the side, back or front 
of the machine. 



926 USE. 

No adjustment of the length of the dolly bar, or the rivet dies, No. 17, is 
required when riveting on various thicknesses of metal. 

The dolly bar has a movement of 45^ in. 

The first 2^ in. is known as the rapid movement, which is set down direct 
by the pressure from the receiver tank of 80 pounds. The last 2^ in. is called 
the effective movement and develops the maximum pressure, giving a uniforrti 
squeeze throughout the entire stroke of the last 2% in., which causes the hot 
rivet in the hole to be very nicely upset, filling the hole solid. 

This pressure is exerted on the dolly bar through the hydro-carbon fluid., 
which is non-freezing, and so long as the operating valve is open, admitting com- 
pressed air to the main piston, the maximum squeeze is maintained on the rivet. 

After a rivet is headed, the dolly bar and the die are positively moved back 
from it by a quick movement of the operating lever. 

Every detail entering into the construction of the Casket Portable Hydro 
Pneumatic Riveter has been studied to make it as "perfect as possible. It is made 
of the finest quality of materials, with specially designed machine tools and thor- 
oughly tested before leaving the shops of the manufacturer. 

The Caskey riveter is built in twenty-one different styles and sizes for driv- 
ing rivets from ^ in. to iJ4 in. All machines are proportioned for using com- 
pressed air at 80 pounds per square inch, and to exert whatever pressure on rivets 
is required. Messrs. Manning, Maxwell & Moore, 85, 87 and 89 Liberty street, 
New York City, are the sole sales agents and will be pleased to send descriptive 
catalogues and further information upon application. 



HAND VERSUS AIR-RIVETING POWER. 



Actual Cost Compared With Hand Work in the Field for the Erection of New 
Work and Repairing; also. Drilling for Reinforcing Old Spans. 



COMMITTEE REPORT. 

To the President and Members of the Association of Railway Superintendents 

of Bridges and Buildings: 

As chairman of this committee I enclose letters received from Messrs. F. 
S. Edinger, S. P. Co., and O. J. Travis, I. C. R. Co., relating to this question, 
which I believe is of interest to all ; personally I am only able to give at present 
my experience in this matter, viz.: 

Since 1890 this company has been steadily replacing all wooden and com- 
bination truss bridges with steel, and up to May, 1899, all riveting in field had 
been done by hand; since May, 1899, we have erected 22 new steel spans of 
various lengths, aggregating in all 2,455 lineal feet; besides this, we have 
repaired several old spans taken down, reinforcing, changing floors, raised to 
safe clearance, etc. In doing this, we have used pneumatic tools for riveting, 
chipping, drilling, reaming, etc. 



USE. 927 

In the erection of the 22 new spans record was kept of the number of 
ivets driven, viz., 80,065. In the repair work we did not pay as close attention to 
number driven, but there were a large number. 

With pneumatic riveting hammers I find two men and one heater can 
average daily (10 hours), 500 rivets, whereas by hand 250 rivets per day was a 
good day's work (more often less), for three men and one heater. One day 
we drove 700 rivets, by using an additional man to take out fitting-up bolts, 
etc. This was the work of one air hammer only. 

In inspecting rivets I find the work far superior to hand work — less loose 
rivets, heads invariably perfect, shank of rivet filling hole, and in every way far 
superior to hand work done by our men, or by others in the past; also work 
can be done readily in places where great difficulty has been experienced with 
hand tools. 

It seems useless to call attention to the benefit of reamed holes in assem- 
bling joints made by pneumatic drills over the "drift-pin work," so much in use, 
where hand riveting prevails; but with the rapidity that air drills run, the 
expense of reaming rivet holes has been reduced to a minimum. 

The pneumatic plant in use on this road for bridge work consists as 
follows : 

One 12 H. P. Fairbanks, Morse & Co. combined gasoline engine and air 
compressor. 

Two galvanized iron water tanks. 
One galvanized iron gasoline tank. 
One boiler iron main reservoir, "large." 
One boiler iron auxiliary reservoir, "small." 

All necessary fittings, etc., and mounted on box car, one No. 2 Boyer 
pneumatic hammer, old style; two New Boyer 000 i 6-16x5 inches, pneumatic 
hand-riveting hammer; two hand steam drills (running them with air), with 
necessary hand, spring, and air dolllies, rivet snaps, forges, drill bits, reamers, 
and other small tools necessary to this class of work. 

The 12 H. P. gasoline engine and air compressor furnishes more than 
enough air to operate all of our tools at the same time. By using the small 
reservoir at bridge and main reservoir on car, and operating at 90 pounds pres- 
sure, we have had in use at one time three hammers, two drills, two heated 
forges, and one blacksmith forge, and have been able to get full capacity out of 
all of them. We have now ordered additional tools, as we find we have sufficient 
power to operate them, especially when cutting out the old steam drills. 

In starting we obtained one No. 2, old style, Boyer hammer, which had 
been in use by another department; this hammer we repaired, and in "Cost of 
Plants," referred to later, we have valued same at half price after repaired. 
Bought two 0000 New Boyer hammers, i 516x5, and last month we ordered a 
No. 2 Boyer piston drill and a latest improved New Boyer long-stroke hammer; 
this hammer and drill I have seen in actual service, and think they are as near 
perfect as it is possible to get. In using these hammers, we find they are free 
from vibration or concussion that had been somewhat of a drawback to pneu- 
matic hammers I have noticed in the past. We use hand riveters only in field 
work on bridges, as we have not driven over ^-inch diameter rivets, and think 



I 



928 USE. 

in such class of work it is more economical than a yoke riveter. In handling 
larger rivets, repairing or rebuilding work done in yards or shops, a yoke riveter 
could be worked to good advantage. In field work there were many difficulties 
when doing hand work that would cause delays that are now overcome quickly 
by use of air. In chipping, cutting out, reaming, drilling, etc., work can be done 
in a fraction of the time that it used to take, and when done you have a good, 
presentable piece of work; in fact, I consider pneumatic tools are so far ahead 
and superior to hand work in everything that it is practically unnecessary to 
dilate their uses. 

It costs us the same to spur out at bridge site, as we always spurred out 
when running a hand gang, and by increasing pipe line we can invariably find 
a good location for the outfit cars with small expense. 

In putting in staging or falsework for riveters we find the cost is less, 
and by doing the work faster by air enables slow orders, or delays to movement 
of trains, to be reduced, and the slowing up or stopping of a train as an item of 
expense to railway companies. 

For your information I have compiled some data on this question, showing 
actual cost of work. We will take up first cost of pneumatic plant. In explana- 
tion, would state, I only show increased cost of plant that, in both hand or air, 
work tools in common ; that is, forges, dollies, chisels, snaps, and all such tools, 
do f'"- appear in this comparison, as one practically offsets the other. 

difficulty i . . . , . 

, . , , J- f'^v air compressor, reservoirs, machinery, water 

driven by hand, ihe i.^ / ^ 

, , ^^ ^, ,-"unted m car $1,073.00 

are very much better than can be lua. .„ ' 

'^ -iv perfect. '' ' ^"^.oo 

Total cosL ^x^^^l.^^ ^or"^..^.7... $1,700.00 

Cost to maintain since May, 1899: 

Repairs to combined engine and air compressor $34.00 

Repairs to new hammers 6.30 

Repairs to old hammers and drills 9.00 

Total cost of repairs $49-30 

Proportion of cost of plant chargeable to work per day, on basis of 20 
per cent, depreciation per year : 
Twenty per cent, of 1,700 = per year $340, or per day basis, 313 working days 

equals year, $1.09. 
Cost to maintain since May, 1899, $49.30, 
Or per month, i-i7th of $49.30 = $2.90, 
Per day, 26 days to month, 11 cts. 

Cost to operate gasoline engine and compressor per day: 

Fifteen gasoline, at 1 1 1-5 cts $r.68 

Oil, waste, etc 12 

$1.80 
Total cost to operate plant per day $3.0q 



USE. 929 

On basis of running three rivet hammers and forges equal cost for one 

hammer of $1.00 

Oil for hammer, estimated amount per day 12 

Labor two men, at $2.40 per day 4.80 

Labor one man, $2.20 per day 2.20 

Total cost to operate one hammer per day $8.12 

Cost of riveting by hand (as noted on commencement of this detail, there 
are no charges for tools, as the small tools, forges, etc., not shown in riveting 
by air, practically offsets tools in riveting by hand) : 

Labor two men, at $2.40 per day $4.80 

Labor two men, at $2.20 per day 4.40 

Total cost of hand-rivet gang per day $9.20 

Men with pneumatic riveter will average 500 rivets per day for $8.12, or 
per hundred, $1.62. 

Men with hand power average 250 rivets per day for $9.20, or per hun- 
dred, $3.68. 

The above figures demonstrate that it costs more than double to drive 
rivets by hand than by using pneumatic tools. 

Another point when you have a compressor outfit, when rebuilding old 
bridges, by putting in a sand blast you are able to eradicate all rust ?rpeirate -.l 
you will find in- all cases on old iron, which it is practicallv. -^,,inaps not reducing' 
hand. This leaves iron in perfect condition to - cne work, 
that rust spots have not been hidden ^'oOring all bolt holes in bridge floor tiip^' 

In closing, will state I thitri^ .*^b« drill. This results in a savipc.inatic plant 
is one of the best investments a railroad *cV.'"^"*.r.c, especially now that steel 
structures are so much in evidence on all first-class roads. 

A. B. Manning, Chairman Committee. 

I am very much interested in the subject, "Hand vs. Air Riveting Power 
Used," and am glad of the opportunity to exchange ideas and experiences with 
others who are using pneumatic tools in field work. 

At present we have two complete pneumatic plants in the field, each con- 
sisting of a i2-horse-power gasoline driven compressor and tools. The first 
plant which we purchased consisted of one compressor, two pneumatic yoke 
riveters, two pneumatic riveting hammers, and two air drills, one of which was 
fitted with angle gear for getting into corners not accessible to the drill proper. 

The first work done with the pneumatic tools was a cover plate job on a 
200-feet-through iron span, which required the drilling of about 6,000 holes 15-16 
inch diameter through ^ inch to ]/2 inch of metal. 

Including the cost of setting up the plant for the first time, which was 
unusually great owing to the inexperience of all hands, the work was done with 
a saving of about 25 per cent, on the cost of doing the work by hand. 

We found that the yoke riveters answered the purpose very well in riveting 
cover plates and other straight work where, when once suspended, they would 
reach a number of rivets, but they were great time consumers when it was 
necessary to move frequently. 



930 USE. 

The riveting hammers which were quick acting and short stroke did not 
give good results — the blow being too light to upset the shank of the rivet to fill 
the hole, and the concussion of the hammer was very distressing to the operator. 

We have since secured hammers which have a long, heavy stroke with 
which we get satisfactory results as to the quality of the work, and the effect 
on the operator is not injurious. 

We have two plants in use at the present time. 

The one used by the steel bridge erecting gang consists of the following 
tools : 

One i2-horse-power gasoline driven air compressor. 

Five long-stroke pneumatic hammers. 

One pneumatic yoke riveter. 

One pneumatic clipping hammer. 

Two' pneumatic drills. 

Together with the usual complement of forges and holding-on appliances 
used in hand riveting. 

The yoke riveter holds as well as drives the rivet. 

With the long stroke hammers we use the usual suspended dolly-bars 
spring-dollies, or lever-dollies, as may be best suited to the condition — the samel 
apt^liances as would be used were the rivets to be driven by hand — and no mort i 
uifficult> ;s experienced in holding the rivets up to the work than were they to be jj 
driven by hand, iiit i.^-^-ors upset the rivets well into the hole and the head.^ I 
are very much better than can be ma Jo \)y hand, in fact, nearly all heads are abs- 
iut^!y perfect. 

Two men IV,"^ 2t heater form a liveting gang, and they drive double the 
number of rivets per day than the gang of three men and a heater where driven 
by hand. 

Where there are a great many rivets of one length to drive, as in lattice 
girders, water tanks, etc., we use a portable furnace with an air blast, and one 
heater supplies two riveting gangs with hot rivets. 

The amount of staging required, from which to drive rivets with pneumatic 
tools, is very much less than is required for hand riveting, as it is only necessary 
to provide seats or standing room for two men, for which oft-times a single 
plank suffices. In riveting viaduct towers, laterals in spans, etc., where there 
are only a few rivets to be driven in a place, the saving on erection of staging 
alone is a very considerable item. 

We now have the air compressor set up in one end of a 50-foot standard 
tool and material car which, in addition to carrying the compressor, receivers, 
circulating tanks, and pneumatic tools, serves to transport other tools and rigging 
from one bridge to another. 

We use a Wharton climb-over switch, which is dropped between the rails 
temporarily, and the car is spurred out on a temporary track, as near to the 
work as is practicable. This saves the expense of handling and setting up the 
plant on the ground for each bridge, and is much cheaper. 

With plenty of storage room for compressed air, so that the pressure will 
not run down suddenly, we can operate five riveting hammers at once, with a 



USE. 931 

i2-horse-power compressor or two drills and two hammers without reducing the 
pressure to less than 75 pounds. 

The drills use a great deal more air than the hammers from the fact that 
they run uninterruptedly, while the hammers when driving 50 rivets of %-inch 
diameter per minute are using air only about 5 per cent, of the time, which gives 
the compressor a chance to catch up. 

We have a storage capacity of about 80 cu. ft., and I think we could use 
one or two more riveting hammers by increasing the capacity of our compressed 
air receivers, as the compressor is frequently cut out by reason of the pressure 
being at maximum (90 lbs.) and the relief valve open. 

With pneumatic tools a great many rivets can be readily driven in places 
which would be inaccessible to hand tools, from the fact that a rivet can be 
driven where there is room to insert the hammer, which is about 20 inches long. 

The chipping hammer is frequently useful in trimming and capping, and 
with it all anchor bolt holes in masonry, up to one inch diameter, are drilled by 
simply inserting an X pointed drill and holding it up to the work. Larger holes 
are drilled with the heavier hammers. There is a saving of about 25 to 40 per 
cent, over the cost of hand work in drilling these holes. 

In fitting up the work ready for riveting, a reamer is used in the drills, 
which one man readily handles, and with which all mis-matched holes are reamed, 
and which insures a full bearing for the rivet and does not burr and separate the 
plates as is the case where drift pins are used. This, while perhaps not reducing 
the cost very much, improves the character of the work. 

We also use the air drills for boring all bolt holes in bridge floor timbers 
by inserting an auger in place of the drill. This results in a saving over the cost 
of hand boring of about 50 per cent., which could be further increased, I think, 
by using the pneumatic boring machines, which run at higher speed and are more 
convenient to handle. 

The cost of fitting up and riveting on new steel bridges (all rivets ^-inch) 
averages to date 35 per cent, less than if the work had been done by hand for all 
work done since we have had the pneumatic tools in use. Work now being 
done with pneumatic plant costs 40 per cent, less than hand work, and we expect 
to still further increase this percentage as the men become more expert with the 
tools. 

The character of the work is much better than we have been able to do 
by hand. 

In case the work is of too great magnitude for one plant, we install both 
compressors and combine all of the tools, but usually one plant is sufficient. 
When not engaged on bridge work, we use our second plant in the erection of 
^ steel tanks and in timber work, such as cofferdams, grillages, slip sheathing, etc., 
where there is a great deal of boring to do. In the erection of steel tanks we use 
the yoke riveter. For the horizontal seams the yoke is hung on rollers which 
roll on the top edge of the sheet, and for the vertical seams the yoke is suspended 
by means of light differential pulleys which allow of adjustment of the yoke to 
the proper height. The chipping hammers are used for calking. 

The saving in pneumatic over hand work on a 60,000 gallon tank is about 
25 per cent. 



932 USE. 

My experience with pneumatic tools has demonstrated to my entire satis- 
faction that all work to which they are applicable can be done much cheaper and 
also much better than by hand, 

P. S. Edinger, Member of Committee. 

With reference to comparison between hand riveting and air machine 
riveting and drilling, I would say this is a subject where I would consider com- 
parisons odious. I have had one 12-horse-power and one 22-horse-power gaso- 
line compressor at work. The former for nearly two years, the latter for nearly 
a year on various kinds of work; reinforcing, drilling, riveting and chipping, 
both in the field and shop. All air work has been done with a most satisfactory 
measure of economy over hand work. We have done over five or six times as 
much drilling with a like number of men as we were able to do with rachets, 
and in places inaccessible to hand rachets, we do over twice to three times as 
much riveting with air as we can do by hand, and do the work 50 per cent, better. 
In fact, I cannot say too much in favor of the air machines. They are all that 
could be desired. 

I may add, however, that I have substituted the latest patterns of hammers 
as fast as they have been improved, and with the best results. 

O. J. Travis, Member of Committee. 
— Age of Steel. 



DRILLING AND RIVETING ON THE ELEVATED RAILROAD, NEW 

YORK. 

In connection with the strengthening of the girders on the Manhattan 
Elevated Railway, which has lately been effected, it was found that considerable 
economy could be obtained by the use of pneumatic tools, and it was in conse- 
quence decided to install a gasoline driven air compressor, together with a pneu- 
matic riveter and a pneumatic drill. The air compressor capacity being limited, 
the question of the consumption of air of the tools used became of considerable 
importance, and a riveter made by the Q. & C. Company and a drill made by the 
Standard Pneumatic Tool Co. were chosen as those satisfying the conditions. 

The test for air consumption was made by pumping up the receiver to a 
certain pressure, then cutting off the compressor and driving the tools entirely 
from the air contained in the receiver while certain operations were performed. 
By noting the drop of the pressure the air consumption of the tool while doing 
the observed work could thus be ascertained by the well known formula of the 
number of cubic feet of free air contained in the reservoir at different pressures. • 
Thus, supposing the reservoir had a capacity of 10 cubic feet and contained air at 
a gauge pressure of 90 pounds : This would correspond to an absolute pressure 
of 105 pounds, or 7 atmospheres absolute, and the number of cubic feet of free air 
contained in the reservoir would therefore be 70. At a pressure of 30 pounds 
the same reservoir should be filled with air at a pressure of 3 atmospheres abso- 
lute and the cubic feet of free air contained therein would therefore be 30. If 
in running a tool the pressure were reduced from 90 to 30 pounds, there wou|d 



USE. 



933 



therefore have been used 40 cubic feet of free air. While this test is not absolutely 
correct, since pneumatic tools are usually designed for a pressure of about 80 to 
90 pounds, and would consequently work less efficiently at the lower pressures to 
which the reservoir might be reduced, it offers a fairly accurate comparative test 
of the different types of tools. 

With respect to the riveter : The rivets driven are ^-inch in diameter in 
13-16-inch holes, and in driving 25 rivets the average consumption of free air per 




FIG. 368 — DRILLING AND RIVETING ELEVATED R. R. STRUCTURE. 



rivet was 5 cubic feet of free air. In driving this number of rivets the pressure 
was reduced considerably, but this may be taken as a fair indication of what is 
required for this size of rivet with a riveter such as used on this work. When 
the time of riveting is taken into account occupied by these machines, viz. : about 
6 to 7 seconds with this size of rivet, the air consumption as measured corre- 
sponds very closely with that figured by the cylinder capacity of the riveter, which 
is 50 cubic feet of free air per minute for continuous working. The measured 
consumption, 5 feet in 6 or 7 seconds, is slightly less than this, which is easily 
accounted for by the fact that there is a certain amount of wire drawing through 



934 



USE. 



the ports admitting air to the cylinder at the high velocities at which these ma- 
chines operate. ** 

The makers of this appliance have devoted considerable attention to the 
question of pneumatic riveting and have found that the weight of the hammer 
employed in riveting is an important point with regard to the quality of the work 




' 



FIG. 369 — RIVETING WITH YOKE RIVETER. 



done. If a rivet is hit with a light hammer, irrespective of its velocity, the rivet 
is flattened out on the end that is hit, but not upset or thickened near the head. 
In other words, the effect is to squeeze the plates leaving a loose shank. If hit 
with a slightly heavier hammer, the flattening process is less marked and there is 
a greater tendency to upset the rivet throughout its entire length, the action being 




USE. 935 

o squeeze the plates and fill the holes. If hit with a very heavy hammer in pro- 
portion to the size of the rivet, the head is flattened but slightly, while the rivet is 
evenly upset throughout its entire length. For these reasons they have adopted a 
weight of hammer in their pneumatic riveting machines that is practically the 
same as used in hand riveting. 

In a machine for driving ^-inch or %-inch rivets, the weight of the ham- 
mer is 4^ pounds; while in the pneumatic riveter for rivets up to i%-inch 
diameter, a hammer is used weighing 7^ pounds. With such weights of striking 
hammers as these, the rivet is not merely flattened only on the head, but thor- 
oughly upset throughout its entire length, and if properly heated, will fill the holes 
completely, doing work that is equal in quality to that effected by pressure 
machines. 

In pneumatic riveting, it is important that the rivet should be rather dif- 
ferently heated to the way that is usual for hand riveting. They require to be bet- 
ter heated throughout their length and only slightly hotter on the end that is to 
be driven. The reason for this is, that the best part of the upsetting is done in 
the first few blows and that if the metal is much softer at the end than toward 




FIG. 370 — PNEUMATIC RIVETING HAMMER. 



the head, the harder metal near the head cannot be upset through the softer. 
Excessive heat is not required, but simply a more even heat throughout the length 
of the rivet than in hand riveting. Then again, if the holes are not good, and the 
rivet when put in is not square with the plate, the riveter should be skewed over 
so as to drive the rivet back concentric with the hole before hammering is com- 
menced. If the riveter is started working on such a rivet, the first few blows 
tend to bend the rivet into a still worse shape and it is then impossible to make 
the head true with the remainder of the rivet. 

Dies also require attention : The right size die must be used, or rather the 
proper length of stock used on the rivet to thoroughly fill the dies, as machine 
riveting is different from hand riveting in this respect. It is rather similar to 
pressure work, and if the rivet does not properly fill the die, the edge of the die 
coming on the sheet prevents the rivet from being thoroughly upset. The Q. & C. 
Company have given cdnsiderable attention to this and other details, such as 
valves and snap catches, methods of working, etc., and have developed their 



936 USE. 

tools to a point where they are ready to guarantee their machines to drive rivets 
as large as iJ4-inch in diameter and thoroughly upset them in the sheets, giving 
results equal to pressure riveting. These tools are all of the valveless type in 
which the piston controls the admission of air above and below it, and no valve is 
used except that to turn the air on and ofif. Such a machine is exceedingly 
simple in construction and it can be taken apart for cleaning or inspection by the 
men employed on the work, without the necessity of engaging the services of a 
skilled mechanic. The construction of these machines admit of the use of a pipe 
yoke on any gap, some of them being made as large as lo feet without the slightest 
trouble. Such a yoke is, of course, exceedingly light, and such riveters are not 
only especially adaptable to work where the riveter has to be moved about with- 
out extensive staging, but frequently it can be used where a machine entailing a 
heavy or girder form of yoke would be entirely out of the question. 



PORTABLE PNEUMATIC RIVETERS IN SHIP-BUILDING.* 

Probably the hardest manual labor in all the various operations in building 
a ship is that of riveting. Combined with this is an amount of technical skill 
acquired only by long and arduous apprenticeship at the trade, and varying with 
the class of rivets driven. Like the stone-c.utter who can only learn to do first-class 
work on one particular stone, and is at a loss, for instance, on marble, if trained 
to granite, so a first-class shell riveter cannot properly drive inside rivets, and 
vice versa; while the boiler riveter, however good he may be at his own work, 
is of little use on any part of the ship's hull. With such conditions, a difficult 
trade to learn, a hard and exhausting one to follow, wearing a man out in his 
youth, for no one ever saw *an old riveter — although in other trades age itself 
is not necessarily a bar — wages are inevitablj^ high, and most of the work is done 
by the piece. When the work is to be had, therefore, the riveter makes a great 
deal of money, but at the expense of his vital energies, which he is too apt to 
attempt to restore by stimulants, especially as his work is done almost entirely, 
from the nature of the case, in the open air, exposed to the heat of summer and 
the cold of winter. 

The tools with which he works are furnished entirely by the yard, so that, 
unlike other mechanics, he is not obliged to have anything of his own, while, as 
rivets are rivets the world over, little familiarity with the customs of any par- 
ticular yard is required of him, and he has not much incentive to remain in one 
place to establish relations of amity and mutual esteem with his superiors. 

The riveters, therefore, have been extremely independent, arrogant, and 
high-handed in their relations with the masters, giving more trouble than all 
the other classes of labor in a yard put together. In addition to this, the rapidly 
increasing size of ships, with the corresponding necessity for heavier plating, 
doublings, etc., requires the use of larger and longer rivets, which cannot be 
properly closed down by hand, however skilful or willing the men may be. 

For all these reasons, in the yard of the Chicago Shipbuilding Company, 
of which I am the manager, some three years ago a determined effort was begun 



* Read at the Fortieth Session of tbe Institution of Naval Architects. 



1 



USE. 



937 



'-^* and an extended series of experiments entered upon to develop machinery 
capable of being operated by unskilled labor, by which all the rivets in a ship 
could be driven, which effort has been entirely sucessful, so that in the last ship 
we have completed there were a little over 250,000 rivets so driven out of a total 
of 340,000. But for insufficient air supply the proportion would have been 
greater. The decision to use compressed air for the operation of the machines, 
instead of hydraulic or electrical power, was made for several reasons. The 
severe winter climate of Chicago is against the use of hydraulic machinery in 
the open air, besides which we were aware that hydraulic compression riveters 
had" never made much headway in British yards, though long in the market, and 
it seemed wiser to try a new line. Electricity, although advancing by leaps and 
bounds, is an intricate science in itself, with which we are not familiar enough 
to see much promise in it, and all electrical appliances are very costly and some- 
what delicate, apparently unsuited to the rough handling inseparable from ship 
work. More important, however, was the fact that air can be used for chipping 



'^EK^B^A^L^ 


llpi 


M 




'^ y y^H .^^3 


si 




^9^-" -^^ ^ "^-**-^z2 




^M. 


*f^%*^ 


^ 



FIG. 371 — SMALL YOKE RIVETER. 



and caulking hammers, for drills and reamers, and for hoists, as well as for 
ventilating and cooling confined places, so that a compressing plant is a necessity 
in any event, while we, of course, knew that pneumatic compression riveters are 
universally used and indispensable in American bridge shops. 

We had in use already at that time a stationary steam riveter of the ordi- 
nary type driving rivets in such proportions of the ship as could be assembled 
and handled as a whole. Eighteen hundred rivets is an ordinary day's work of 
ten hours on this machine, at a cost of one-half cent apiece. A very short ex- 
perience with compression riveters showed that their great weight — reaching over 
2,500 lb. for 6 ft. gap — interfered too much with facility of handling to make them 
either useful* or economical. We then turned our attention to the pneumatic 
hammer, consisting of a cylinder in which a piston reciprocates, delivering an 
almost continuous series of blows against the end of the chisel, caulking tool, or 
rivet die. The hammer is light, powerful, short enough to go between frames, 
and small enough in diameter to get at rivets in corner angle. For small rivets 
it can be held in the hand, though the work is severe. It is, however, almost 



938 



USE. 



impossible to hold on to the rivet by hand, the heavy holding-on hammer being 
fairly jarred off the head of the rivet by the rivet by the rapidity of the blows 
from the pneumatic hammer, giving the holder-on no opportunity to bring his 
tool back into position between blows as in hand riveting. 

We quickly devised a simple pneumatic holder-on, however, which admir- 
ably serves the purpose, consisting only of a cylinder carrying a piston, behind 
which air is admitted, the rod extending through the front head and being cupped 
out to go over the head of the rivet. A piece of pipe secured to the cylinder 
braces it against any convenient support. Combining these two machines with 
a yoke, the hammer being mounted on one arm and the holder-on on the other, 
makes a self-contained machine in which the yoke itself can be made very light, 
as it has to resist only the pressure of the air against the end of the holder-on 
cylinder and the reaction of the hammer blows. 

Various sizes of these yoke riveters are used, and the weights are as fol- 
lows for the depths of gap given, the yoke being made of pipe for the larger 




FIG. 372 — YOKE RIVETER. 



sizes: — 9 in., 83 lb.; 515^ in., 160 lb.; 70 in., 220 lb. It is very evident, therefore, 
that these riveters are portable in the highest degree. In fact, in the greater 
number of places they are moved about by two men entirely by hand, the cross- 
bar in the throat of those of larger gap forming a slide, and assisting in the 
movement. Occasionally they are suspended on a trolley from a light frame- 
work of pipe. A variation of the device is to mount the hammer in a cylinder 
as a piston, behind which air is admitted to force the hammer forward as the 
rivet point is beaten down, the die on the opposite arm of the yoke being then 
solid, and may be small to get into contracted places. For driving the rivets 
connecting frames and brackets at the tank top of a double-bottom ship, the yoke 
is mounted on a pair of rough wooden wheels for ease in handling. 

The above descriptions will, I trust, sufficiently make plain our methods 
for all rivets which can be reached on both sides by a yoke or gap riveter. There 
remain three classes of rivets in a ship, as follows: (i) Those through decks and 
tank tops, mostly countersunk, and all driven vertically downwards from above; 
(2) bulkhead rivets — other than those near the top, or adjoining openings, which 



USE. 



939 



can be reached by a yoke — nearly all with full heads; (3) those in the outside 
shell of the ship, all countersunk. These three classes must be reached by 
riveters on one side and holders-on on the other, without any connection what- 
ever between them. 

The first class are most easily driven, and for them the hammer is mounted 
on a bent pipe, with a pair of wheels at the bend. The operator raises a handle 
to bring the flat die on to the rivet, and, the bend of the pipe being loaded with 
lead, has only to bear down upon it in driving. A second man, with a pneu- 
matic chipping hammer, cuts off the surplus metal, and, the riveting hammer 
being brought back, a few seconds complete the operation. In this case the 
pneumatic holder-on is operated from below by a third man, being braced against 
the bottom of the ship or the next deck below. For the second class, the hammer 
is fastened to the end of a wooden beam which slides freely on a supporting 
'Miidbplted to the bulkhead, an adjustable rod at the other end governing the dis- 
tance of the hammer from the rivet point. A large number of rivets can be 




FIG- Z7Z — ^LARGE YOKE RIVETER. 



reached without shifting the stud. It is necessary, of course, to use the form of 
hammer described above with the air pressure behind it, and, as the die is cupped 
out to form the snap point, there is no tendency to slip off the point. The holder- 
on is mounted in the same way on the other side of the bulkhead. 

We now come to the third class, or shell rivets, which in many respects 
are the most important rivets in the ship, requiring the most careful workman- 
ship and the best finish. It is evident, at the start, that the varying thicknesses 
of plates, frame flanges and liners, and especially the depth of countersink, render 
it impracticable to so gauge the length of rivet used that there will always be 
just enough metal to properly fill the countersink and finish the point, and that, 
therefore, as in hand riveting, a longer rivet must be used, and after the point 
is beaten down with the surplus metal crowded off to one side, this surface must 
be chipped off, and then the point finished up, rounded slightly, and any seams 
between the rivet and the plate driven together and closed. To do this a certain 
amount of freedom of motion must be allowed in the hammer, so that its axis may 
be inclined at a slight angle in any direction with the axis of the rivet itself. This 



940 USE. 

result is attained by mounting the hammer in gimbals on the end of a bar, instead 
of its being immovably fastened to it, as in the bulkhead riveter. For bottom 
rivets this bar is attached, by a central bolt on which it revolves, to a trolley run- 
ning inside a slotted piece of pipe, which is either bolted to the bottom of the ship 
or held up against it by a simple pneumatic jack at each end. The bar carries at 
its other end an adjustable brace as in the bulkhead riveter, and there is, of course, 
an air cylinder behind the hammer to force it in as the point of the rivet is beaten 
down. 

At one setting many rivets can be reached, and the whole arrangement is 
very satisfactory, a pneumatic holder-on being used inside, and an ordinary 
pneumatic hammer being used to cut off the surplus metal before final finishing 

It is evident that the freedom of movement of the hammer can be secured 
in other ways, such as a ball-and-socket joint of large radius, but we have found 
the gimbal mounting more satisfactory, and all that can be desired. While the 
same arrangement can be used for the side of a ship, it is not very satisfactory 
there, and a different one is desirable. In this the bar carrying the hammer is 
vertical, and is fastened to a bored-out tee, sliding freely on a horizontal pipe. 
This pipe is prevented from moving away from the ship by vertical pieces of bar 
or angle iron at each end, bolted to the ship parallel to the side and 8 in. or lo in. 
away from it. The pipe is hung from pulleys above, and counterweighted so that 
it moves freely up or down. By the vertical movement of this pipe and the hori- 
zontal movement of the sliding tee any rivet can be reached from the gunwale 
of the lower turn of the bilge, and for a length of about lo ft., without shifting 
ihe rig. Inside the ship a couple of rough wood stanchions are bolted or wedged 
in position for guides, and a counterweighted piece of 2 in. plank moves against 
them in unison with the riveter and forms the brace for the pneumatic holder-on. 
which is easily moved by hand into proper position. 

The quality of the work done by all these machines, both inside and shell, 
is first class in every respect, and far superior to hand work, and such is the 
unanimous opinion of the inspectors who have been and are on duty in our yard. 
That this is natural appears from several considerations. The rivets are closed 
down more rapidly and at a much higher temperature, and, as it is always easy 
to bring the axis of the hammer in line with the axis of the rivet, and, in fact, 
natural for the men to so bring it, the rivet is plugged at once by the first blows of 
the hammer, thoroughly filling the hole throughout, before the point begins to 
form. The tendency of hand riveters to save labor by forming the point without 
thorough plugging, leaving a rivet which, though looking all right and passing 
the tester, is liable to loosen afterwards in service from the constant jar and 
vibration of the hull, is, therefore, avoided. In many confined places, also, where 
only one man can strike, and the space for the swing of the hammer is limited to 
the frame spacing or less, hand rivets are very apt to be poorly driven, but it is 
evident that such considerations do not affect the machine, and that, if the pneu- 
matic hammer can get to the rivet at all, it is as well put in as in the most open 
parts of the work. 

As to the cost of the work, I submit the following figures, from the last 
ship completed in our yard : 



USE. 



941 



Inside Rivets. — All ^ in. 

Hand, piecework 25,073 Av. cost, 3.16c 

Hand, day work 9,255 " 

Air 151,167 

Steam 23,544 

Shell Rivets. — J/^ in. and i in. 

Hand, piecework Si,3o6 Av. cost, 

Hand, day work 4,314 " 

^ir 74,493 



8.57c 
2.06c 
0.5 1 c 

3-99C 
7.69c 
2.96c 



The amount that should be added to the machine cost to cover interest, 
maintenance of plant, and operation of compressor, is undoubtedly much greater 
than the corresponding amount for hand riveting, which is little beyond hammer 
heads and handles ; but I cannot give it exactly, as we were using much air at 
the same time for drilling, reaming and caulking, as well as for blowing the 




^^^- 375 — BABCOCK-GUNNELL SHELL RIVETER. 



rivet-heating forges — so much so, in fact, that we exceeded the capacity of the 
two compressors in use, and not only had to stop putting on more machines 
and go back to hand riveting, but, for a large portion of the time could not main- 
tain more than 70 lb. pressure in the air mains, which seriously impaired the 
efficiency of the hammers. We had an air capacity of about 850 cubic feet of free 
air per minute at 100 lb. pressure, but we have now nearly completed a new 
compressor of 3,000 ft. capacity, to work at 125 lb. pressure, and anticipate much 
better results hereafter. It is only fair to call attention to the fact that most 
lake freight vessels, like the one referred to above, are of very full model, with a 
large number of frames exactly alike amidships, and that they are launched 
broadside on, and therefore stand level on the stocks, both of which conditions 
are favorable to the use of these machines, especially of the shell riveters. 
Against this, however, it is equally proper to state that much of the development 
of the inside riveters took place on the boat referred to above, and that the shell 
riveters had never been tried at all until they commenced on her bottom plating. 
In the latter case, therefore, all the experimenting and working out of the appli- 



942 



USE. 



ances for rapidly and economically handling the machines, as well as breaking 
in the men to use them, came on that boat, and the cost appears in the above 
statement. It must be remembered also that the men who have worked all these 
machines are not riveters, not even mechanics, but only laborers, and were not 
on piecework. 

The largest rivets we have as yet driven with these machines are i in. in 
diameter. But there is no reason whatever why larger sizes cannot be driven 
with equally satisfactory results. It is only necessary to use a larger hammer, 
one of greater diameter and longer stroke. In gasometer work in America, this 
has been done already with gap riveters and i^ in. rivets closed with perfect 
success, and there can be no question but that a larger size shell riveter will 
handle rivets of equal diameter with the same facility, the somewhat greater 
weight of the machine being no disadvantage, as it is counterbalanced and does 
not come upon the operator at all. 

In Chicago we are still experimenting with and developing these tools, and 
hope to much further increase their efficiency and economy. I have thought, 
however, that the members of the institution might be glad to know of the results 
already accomplished in a matter of such importance to shipbuilding. 

W. J. Babcock, Member. 



NEW PORTABLE PNEUMATIC RAMMER.* 

The pleasure I experience in addressing this distinguished company is en- 
hanced by the fact that I am to have the privilege of bringing to its notice an 
article of such novelty and unquestionable value, that I am sure of your injffest 
and attention. ' ■"- ' "^* 

No doubt many of my hearers have frequently stood over a deep pit in a 
foundry, and watched with curious interest a gang of laborers ramming up in an 
aimless, monotonous fashion some large mould, and wondered that in this age of 
advanced mechanical ideas no one has had the thought to apply to this class of 
work some device which would take advantage of the great field for econon^.. 

The new rammer which has come in response to this call, is from the bfaih 
of a thoroughly practical, mechanical man, whose knowledge of the advantage of 
labor-saving devices— and the proper application of them, has been derived from a 
wide and varied experience. The man to whom I refer is Mr. Joseph C. Crimp, 
Superintendent of the Power and Plant Repair Department of the Wm. tramp & 
Sons Ship and Engine Building Company, of this city. 

It was, therefore, quite proper and natural that the idea of introducing ap 
article of such mechanical neatness and such commercial value, should have orig- 
inated in the mind of a thoughtful and practical man. 

Convinced that it was in his power to perfect a machine that would be ai 
inestimable value to me in the foundry, I kept nagging at him on the subject, and 
about a year ago I succeeded in getting him enough interested to put his ideis 
and thought into tangible shape, the result of which is this Portable Pp«umd.tic 

• Paper read at a meeting of the Foundrymen'e Aesociation, Philadelphia, April 6, 1898. 



w 



USE. 943 

mmer, which will practically revolutionize loam moulding and, to a great ex- 
ent, large green sand work. 

For fully a year, Mr. Cramp worked and puzzled and struggled on ; I criti • 
ising, Mr. Cramp trying again and again, disappointed but not discouraged, until 
t last he succeeded in giving me a tool that left nothing to criticise, and the 
ammer was a success. 

The portable rammer consists of two vertical cylinders, held apart by 

tanchions containing pistons driven either by steam or compressed air, which is 

egulated by a simple but ingeniously contrived Corliss valve. The size of the 

linder is 3^ inches, the length of stroke is 4H inches, and with an air pressure 

of 35 lbs. per sq. inch at the piston, it strikes 200 blows per minute, each blow with 

the butt rammer head covering an area equal to seven times the area of an 

rdinary hand-rammer. 

This device which at once may suggest itself as scientific and practical, is 
suspended from a turnbuckle which is attached to a trolley on movable crane, to 
enable it to move with perfect ease to any portion of the pit to be rammed. Power 
is supplied through a flexible hose, tapped from the main pipe, running the entire 
length of the foundry. The crane is portable and can be shifted to any column, 
thereby covering any spot in the shop. 

For the last three months it has been in successful operation every day ram 
ming up moulds of all manner of shapes and sizes, and weights ; indeed, it seems 
almost impossible to describe and explain the vast amount of work it does and 
labor saved. There are very few moulds that I have ever seen that cannot by this 
tool be rammed up in one day. I am at present making some very large pumps 
that require a pit 30 feet long, 14 feet wide and 8 feet deep. According to our 
regular practice it would take about 25 men three days to ram it up ready for 
casting. I very easily, with two machines and 12 men, rammed it up in one day — 
not only saving in money paid for labor, but casting two days earlier, thereby 
saving considerable time in the room occupied by this mould. I also find that it 
increases the capacity of my ovens, for I am able to cast the moulds faster after 
they are dried, and do not have to wait for floor space to put the moulds after they 
are dried. 

The rammer itself is very simple, and has never as yet gotten out of order, 
but is always ready. There are no break-downs, nor giving out of little things, 
which very often occur in new mechanical devices, and cause constant irritation 
to a foreman. 

Most any loom mould can, with four men be rammed up in a day. By this I 
mean any large mould say 10 feet in diameter and 6 to 8 feet deep; of course, 
small ones can be rammed up correspondingly quicker, and the ramming is more 
even and far superior than that done by hand, as you all know laborers, when 
ramming a mould, do so in a sort of aimless way. When the foreman's b^ck is 
turned, the blow struck is not very hard, and very often the casting strains con- 
siderably. Any casting rammed up by this tool will be fully 10 per cent, less in 
weight than when rammed by hand. I have been able to materially reduce my 
laboring force since using the rammer, and the running expenses of the 
shop, for when I have no ramming to do the machine is idle, and at no cost, 
whereas when hand is used you have the men around the shop drawing their pay 



944 



USE. 



just the same. Any tool in a shop to-day that will allow you to do away with 
men is a money saver even if it does not do work any cheaper, for the correct 
and great idea in the management of any business to-day is, to have as few men 
as possible in your shop when you are able to supplant them by modern tools, for 
there are always lulls and times when you have surplus labor. It may be for a 
couple of days, or it may be for a few hours — we try to keep men employed on 
odds and ends because we see we will want them in a few days. I know every 
foreman present will concur with me on this point. 

I have been experimenting with the rammer mostly on ramming up loam 
moulds, but since it has proven its great value there, I have lately been introducing 
it on large green sand work. In bedding in large green sand work, you all know 
the main point is to have a good, evenly rammed bed under it. Thus the rammer 
will do far superior and ■far quicker work than by hand. 

In regard to the firmness of the ramming, it is at once made self-evident 
when you come to vent your bed, and all doubt will at once leave you as regards 
the evenness and hardness of the ramming. Anyone present who has made large 
castings in green sand will at once fully appreciate the ramming of the bed in two 
to three hours that ordinarily would take two moulders and helpers one to two 
aays, and then not done as well as when using the rammer. 

^ I am at present having some pneumatic rammers made to put on in place of 
me butts. I will then commence ramming the moulds up completely with the 
machine. Such is my faith in it, that I have no doubt that in a few months all of 
my large castings in green sand will be rammed up with this new tool; that is, 
with the exception of the cope. How many of you present have hoisted out a 
large casting, and after digging out the pit, taken out your cinders and plates, 
have found a large hole in your floor confronting you. You may need this floor 
space badly, but you have no men to spare to ram it up, and you either have to 
do it at night, or wait until you can spare the laborers to do it. Now, right here 
is where the rammer comes in. You can always spare two men — one to run the 
machine, and one to fill in the sand — and in a very short time you have your pit 
rammed up even with your floor ; there being no soft places for the next casting 
put there to strain, but a good, hard, evenly rammed floor. 

With this rammer, whether the force of the blow is equal to 300 pounds or 
one pound, which can be very easily regulated by the turnbuckle, every blow 
struck will be of uniform force, consequently the sand will be rammed evenly, and 
with the same force throughout every inch of its surface, and no straining of the 
metal in casting can possibly occur. 

Another strange thing about the rammer, although you use it for ram- 
nnng up your moulds, you can change it and use it to dig your pit out, by simply 
putting on a rammer with prongs. This will go around and break up the sand so 
that it can be very easily shoveled out. Instead of having hard digging, you sim- 
ply have shoveling. 

I have already touched lightly on the advantage of reducing as much as 
possible the froce of the men employed in a foundry or, in fact, in any establish 
ment, and if you will permit me to enter a little more deeply into this subject, I 
will give you some reasons. 



USE. 945 

First of all, because of the fewer men you employ the smaller and less 
complicated is your pay roll ; the more will your foreman be relieved from enforc- 
ing discipline and surveillance, and be able to devote his time to perfecting their 
work; there will be less likelihood of strikes occurring, and the less damage if 
they should occur. A machine that will do the work of a man in the same time 
is more valuable than that man. Now this tool will do the work of 15 or 20 men, 
and not only do it better, but in far less time, and when done you simply close a 
valve, and it is at rest until you need it again. 

Before I close, allow me to express a few thoughts on the subject of com- 
pressed air. I mentioned that this rammer could be run either with air or steam ; 
but for ramming in a foundry compressed air is far better power. The day is 
not far distant when it will be more widely used in all of our foundries. The 
pneumatic chipping tool has come to stay, and although my first experience with 
it was not favorable, I have changed my mind since getting the right tool, and I 
can fully recommend its utility and cheapness in chipping castings. The sand 
blast is another appliance that can economically be attached to any air compressor 
and do good work. Most of you appreciate the use of air hoists, and I think " 
traveling crane will, in most foundries give more satisfaction than one run "by 
electricity, for the simple reason that a crane run by air is not so complicated, and 
does not need such skilled labor to run it or keep it in strict repair. Most any 
machinist understands air, and very few electricity. In our foundry this is not 
so apparent, as we have a corps of electricians at work all the time on the ships, 
and these are at my disposal at once, in case of a break-down; but I presume 
most of the foundries are not so well favored. 

My idea in mentioning the use of aii* is to bring to your notice the fact that 
the installing of an air plant to run the rammer is a very useful and paying invest- 
ment, for you will be greatly surprised at the many things to which you will con- 
stantly be applying this power. 

In conclusion, allow me to thank most sincerely the officers of this Associa- 
tion for their polite invitation, the members of this beautiful club for the privi- 
lege it affords, and to you gentlemen, for your marked courtesy and kind atten- 
tion. 

The pneumatic ramfiier is now being manufactured by J. W. Paxson & Co., 
Philadelphia, Pa. George C. Matlack. 



COMPRESSED AIR RIVETING PLANT. 

An interesting application of the use of compressed air may be seen a short 
distance out from the Erie Railroad depot at Jersey City. The Erie Railroad is 
elevating its tracks through the city, r.nd at every street crossing there is an iron 
bridge. The work of riveting these bridges until recently has been done by hand, 
with the usual results that a gang of two men and two boys will drive on an aver- 
age of 300 rivets a day of ten hours. The rivets to be driven are five-eighths 
inch and seven-eighths inch diameter. 

A compressed air riveting plant has now been substituted for the hand 
riveters with the result that one man and three boys arc driving 1,200 five-eighths 



946 



USE. 



inch and i,ooo seven-eighths inch rivets a day, with less effort and in a much more 
satisfactory manner. 

The plant hass now been in operation about one month, and so far has 
proved to be reliable and entirely satisfactory. It consists of a Fairbanks-Morse 
direct connected gasoline engine air compressor of 12 B.H.P., capable of deliver- 
ing 70 cti. ft. of free air at 80 lbs. pressure per minute. The compressor is 
mounted in a box car, together with the water-cooling tank, fuel supply and air 
receiver. The car is drawn up on a side track near the work and the hose car- 
ried up on the structure. This arangement is clearly shown in engraving. The 
car will be seen at the left in the cut, while the men at work with the pneumatic 
riveters are in the foreground. 

The compressor is fitted with an automatic unloading device which opens 
the air cylinder exhaust to the atmosphere when the receiver has reached the re- 




FIG. 2>7^ — RIVETING ON BRIDGE ERIE R. R. ELEVATION. POWER OBTAINED FROM GASO- 
LINE AIR COMPRESSOR IN BOX CAR TO THE LEFT. 



quired pressure; the engine governor then acts and cuts down the fuel supply, 
the speed of the engine remaining constant. 

The pneumatic riveters used are those of the Chicago Pneumatic Tool Co. 
They are somewhat larger than the usual hammers and are designed to set up 
seven-eighths and one-inch rivets. The air used in one of these hammers is 25 
cu. ft. per minute. 

There is also at work a Chicago piston pneumatic drill with which the 
liolcs are reamed out true before the rivet is inserted. This drill works very 
rapidly, and one man readily replaces four men using the old drift pin method of 
aligning holes. 

It will be seen from the foregoing that the seventy-foot compressor plant 
here used will handle two of the large riveters and one drill. 



USE. 



947 



The fuel cost of delivering 70 feet of free air per minute at 80 lbs. is ap- 
proximately 12 cents per hour. The gasoline used is what is known as 74** com- 
mon stove gasoline. 



DRIVING DRIFT PINS WITH A NEW DEVICE. 

An interesting labor-saving appliance which we describe and illustrate, 
has lately been put into practical use by Mr. D. E. Moran, M. E., of New York. 

The contractors for the new water works for the city of Cincinnati had to 
build a caisson 130 ft. in diam. x 3 ft. thick. The platform of this caisson was 
made of timber and required about 70,000 drift pins i in. diam. x 30 in. long to 




FIG. z^^- 



-DRIVING DRIFT PINS BY A COMPRESSED AIR DEVICE. 
IN THE DISTANCE. 



WOOD BORING MACHINE 



948 USE 

make it rigid and to hold the timbers in position. Originally the work of driving 
the drift pins was done by hand and it took a gang of three laborers, each paid 
$1.50 per day, to drive 200 drifts per day. The holes for the drifts were drilled 
with several "Phoenix" Pneumatic wood boring machines built by the C. H. 
Haeseler Co., of Philadelphia, one of which is shown in operation on right hand 
side of cut. The depth of these drift pin holes was 34'' by ^| " diameter, or in 
other words, 4" longer and xV" smaller than the pins themselves. 

Mr. Moran, not satisfied with the progress of the work, conceived the idea 
of using an Ingersoll-Sergeant rock drill to dispense with the manual labor of 
hammering. He mounted a 3^^ in. drill on a derrick, as shown on the illus- 
tration. The piston of the drill carried a hammer striking on an anvil, whose 
bottom was cupped and placed directly over the drift. By means of a double 
windlass the drill could either be raised or lowered and the total weight of the 
drill, with partial weight of the frame, would prevent any recoil when striking. 
The anvil being cupped at the bottom keeps the drill always central above the 
drift, and by means of this appliance he was able to drive an average of 800 
drifts per day with three men, while only 200 could be driven by hand, this being 
done at the same expense with the exception of compressed air power for run- 
ning the drill. The cost of the power, however, was insignificant, as the com- 
pany building the caisson hc.ve several large air com.pressors used for other 
purposes. 

The frame supporting the drill being mounted on wheels, is easily moved 
from one drift pin hole to another, and we are informed that the total cost of the 
frame, with mountings above the original cost of the drill, did not exceed $75. 
Thus, it will be seen that this simple method has not only saved the contractors 
about $2.00 per 100 drifts to be driven, but that it has increased the capacity, or, 
in other words, decreased the time of building the caisson some 75 per cent.' We 
are also informed that the drill did better work than that done by hand labor, as 
the drifts driven mechanically were never bent, while by hand driving they were 
very often bent and tops bruised and required considerable labor and loss of time 
for straightening and final driving home. 



A COLLECTION OF BLACKSMITHS' TOOLS. 

An interesting feature of the last annual convention of the National Rail- 
road Master Blacksmiths' Association was the introduction and description to the 
members of a large variety of labor-saving appliances which one or other of the 
members had devised for assistance in his daily work. Naturally most of these 
devices were in the line of forms for bending, shaping, upsetting and riveting, for 
use on those parts of locomotive and car work upon which a large number of 
processes are necessarily duplicated, and in most instances the tools form a part 
of the equipment of a pneumatic bulldozer or hammer, also of home production. 
Photographs and descriptions of several of these appliances have been collected 
from the secretary and members of that association and are presented here as 
containing valuable suggestions to those who are engaged upon similar work. 



USE. 



949 




X 






^ 








1 


T 


L^a 



i 




950 USE. 

Figures 378 to 381 of the accompanying illustrations show a pneumatic 
machine, a collection of formers for use with it, and some specimens of work 
done. This machine is in use at the shops of the Pittsburg & Lake Erie Railroad 
at Pittsburg, in the blacksmith department, under the direction of Mr. A. W. 
McCaslin. The pneumatic bulldozer was built of scrap . or useless material on 
hand, and consists of two 16-inch cylinders placed tandem fashion on a frame 
made of two lo-inch I-beams, each 8 feet in length, with a piece of 80-pound rail 
riveted on the inside of the web of each beam. The frame is covered with a 
wrought-iron face plate. The piston rod is 4 inches in diameter, and with an air 
pressure of 125 pounds an effective or working pressure of 25,000 pounds is 
obtained from each cylinder, or 50,000 pounds from the two cylinders. In using 
two cylinders upon a machine of this character, Mr. McCaslin states that he 
finds it more satisfactory to place them tandem rather than side by side, for the 
reason that the presure from both is in a direct line. This is particularly valuable 
in upsetting, a class of work for which the machine finds the greatest demand, 
and which is not always satisfactorily met by the steam hammer. 

The machine is capable of eight strokes per minute, and the output of any 
class of article depends upon the heating capacity and the activity of the operator. 

Figure 378 shows the machine in position for bending the lips on drawbar 
yokes. The V-shaped die connected to the piston rod has a cutter upon one si4e, 
which shears off any surplus iron which may result from the bars not being cut 
off to the exact length required. For this purpose Mr. McCaslin originally used 
a tool with compound levers, by which means a pressure of 100,000 pounds was 
obtained. With this arrangement the lip was formed satisfactorily, but it was 
impossible to prevent the upsetting of the bar in the clamp in which it was held. 
In Fig. 380, numbers 9 and 10 are tools for forming the yokes themselves, form 
No. 9 having a bent yoke upon it and the crown-retaining lever lying in front 
of it. 

In Fig. 379 the same machine is shown as arranged for riveting drawbar 
yokes. The hinged apron receives the drawbar as it is dumped from a truck. The 
air hoist, which is suspended above the machine, lifts the apron with the drawbar 
and throws the latter into position for receiving the rivets. The latter are i^ 
inches in diameter. When the riveting is completed the apron is lowered as it was 
raised. It is stated that with 50 pounds' air pressure 150 yokes can be riveted in 
ten hours, and the operation involves no lifting by hand. 

Figure 380 shows a group of forms for various purposes, the number of 
which is being constantly increased. No. i is a tool for upsetting a i^-inch ball 
on the end of 5^-inch rotmd iron for grab-irons. No. 5 (with O representing 
the piston rod) is for completing grab-irons. The capacity is 200 from the bar in 
ten hours. No. 2 is for upsetting the ends of i^-inch truss rods. The capacity 
is 400 in ten hours, or as many as can be handled. No. 3 are forms for bending 
brake lever carriers. These have rollers in the angle or bearing ends, as has also 
No. 10, previously mentioned, to lessen friction on the iron. No. 6 are the forms 
shown on Fig. 381 for bending lips on drawbar yokes. No. 8 is a tool for forming, 
cutting or unlocking pin levers, and No. 10 (next to No. 9) is the tool in which 
the connecting end of the lever is formed, and which is bolted to an angle on the 
face plate of the machine. No. 11 is for forming brake-hanger stirrups. This is 



r 



USE. 



951 



the ordinary hand tool, with auxiliary levers for connecting it to the piston cross- 
bar. No. 12 is for upsetting heads on i->4-inch king or centre pins. The rate is 
te per minute. Nos. 13 and 15 are adjustable tools for bending arch-bars of 
y size or to any angle. No. 14 is the piston crossbar to which the movable parts 
of all formers are bolted. This has rollers on the under side and prevents the 
l^iston from turning. Nos. 20 and 21 are yoke-riveting cup tools. 
^[ There are many other tools of similar character used with this machine, 

■ such as key-way punches, formers for car steps, coach steps, drawbar carriers and 
air brake work. Fig. 381 shows samples of a variety of the work done and also 
an axle straightening lathe and crane combined, which have been built at the 
same shops. 

Fig. 382 is a machine for similar work, which was built by Mr. J. E. Mick, 
of the Baltimore & Ohio Southwestern, at Chillicothe, O. Dies for making draw- 




FIG. 381 AXLE STRAIGHTENING LATHE AND SAMPLES OF BENDING, 

bar pockets and nearly all kinds of plain work have been made for use with it, 
and some of the varieties of finished parts are shown in the engraving. 

Mr. John Coleman, of the Chicago & Northwestern shops at Clinton, la., 
devised the hammer shown in Fig. 383 for use at the spring fire in drawing and 
clipping spring leaves, holding down bands while the sides are driven to place, as 
with a screw press, etc., and a variety of similar light work, in which it has come 
to be recognized as one of the most useful tools in the shop. The cylinder is 6 by 
22 inches and the weight of the hammer and piston rod 300 pounds. It is used 
with an air pressure of 90 pounds. 

The secretary of the Master Blacksmith's Association, Mr. A. L. Wood- 
worth, of the Cincinnati, Hamilton & Dayton, at Lima, O., is the designer of 
the group of tools shown in Fig. 384. The most conspicuous tool in the engraving 
is a former for bending corner steps for freight cars, the lever at the left of the 



952 



USE. 



figure being removed to show the construction of the dies. When in use the 
bedplate of the device is clamped to an anvil, as shown. The movement of the 
levers bends the blank to form the horizontal part of the step, and the offset on 
each arm catches the blank as the lever closes against the bed, thus turning it 
down at the end to whatever distance may be desired. Both ends are bent and 
turned at the same time. With the size of iron used, ^ by 2 inches, it is stated 
that from 250 to 300 steps are made by two men in a fair day's work. It is the 
intention to apply air power and thus about double the capacity. A sample of 
the finished product is shown in the foreground at the right. 

The tool at the left of the engraving is for bending eyebolts, brake-hanger 
hooks and the like. The lever in which the iron is held has a slot for that pur- 
pose, and is pivoted at the end by a lug, which passes through the bedplate and is 




FIG. 382 — PNEUMATIC PRESS FOR BENDI] 



fastened by a cotter pin. The other lever is held by a stationary pin, which forms 
the pivot on which it swings. This lever carries a roller. In operation the iron 
is placed in the slot and a slight movement given to the slotted lever brings the 
body of the bolt central with the eye. The longer lever, with its roller resting 
against the iron, is then carried around, wrapping the blank around the stationary 
pin forming the eye. This tool is also clamped on an anvil when in use, and from 
40 to 50 ^-inch eyebolts may be made in an hour by one man. 

The tool just to the right of the anvil is a very successful device for bend- 
ing collars for the heads of drawbar stems. The size of iron used is f^ by ij^ by 
8 inches long. The mandrel around which the collars are wrapped is 2^ inches 
in diameter and has a lever to hold the iron in place while being bent. The 
lower end of the mandrel passes down through a hole in the plate, as shown. 



USE. 



953 



le device is operated by air. The levers which are attached to the piston rod of 
le air cylinder have at their opposite ends rollers carried by i^-inch bolts 
passing through curved slots in the bed. As soon as the blank is wrapped around 
le mandrel until the center is reached, the curved slots bring the rollers in close 




FIG. 383 — PNEUMATIC HAMMER FOR SPRING WORK. 



together behind the mandrel, thus making the blank form a perfect circle. The 
mandrel is then raised, and the collar falls off. The capacity is limited only by 
the capacity for heating. 

The tool to the extreme right is precisely similar in principle, except that it 
works under the steam hammer, and is intended for bending brake-hanger loops. 



954 



USE. 



In use the plate is bolted in an upright position to the bottom die of the hammer, 
and the arms are hinged to the upper die. The rollers are flanged in order to 
hold the iron close against the plate while bending. 

A considerable number of other tools of a similar class have been developed 
as a result of a necessity for rapid work in the various railway blacksmith shops 
of the country. An indication of the extent to which such tools have been put in 
service is shown by the statement of one railway blacksmith that he has in his 
shop nearly 3,000 forms for bending, forging, etc. The above are given as sug- 



. ^ 


Pj^gB 


^^HH 


^^B 


• 1 jk^^^JM 


^MH^k?e£^^^a9l^^^l 


■j^^HHpBsS 


i^^^^^n 



FIG. 384 — TOOLS FOR BENDING STEPS^ EYEBOLTS, ETC. 

gestive of the ease with which a shop equipment may be increased with small 
initial expense. — Railway Age. 



THE THOMAS PNEUMATIC SYSTEM OF HANDLING RAILWAY 
SWITCHES AND SIGNALS. 

The fundamental feature of this system is the manipulation of the valves 
admitting air to and exhaust it from the working cylinders of railway switches 
and signals by means of pistons of the equalizing type, the pistons being actuated 
by a sudden increase or decrease of the air pressure. 

SWITCHES. 

Fig. 385 is axial section of valves for admitting air to and exhausting it from 
the working cylinders of switch, and also shows section of reservoirs 6 and 6\ 

Fig. 386 is cross- section. 

Fig. 387 is top view of reservoirs and valve seats. 

Fig. 388 is axial view of working cylinder and top view of chests and reser- 
voirs. 

When switch is in its normal position, pressure in controlling pipe 4, chest 
5 and reservpir 6, is at 70 lbs., the pressure in chest 5 and reservoir 6 having 
equalized with the pressure in controlling pipe 4 by means of equalizing port 7; 



USE. 



95! 



chest 5 and reservoir 6 are in communication by means of passages 3, Fig. 387. 
The pressure in controlling pipe 4^, chest 5^, and reservoir 6^, is at 80 lbs., these 
pressures having equalized through feed port 7^, Fig. 385, and ports 3^, Fig. 387. 
Under these conditions, piston 8 is to the right ; and F end of cylinder i, Fig. 388 
is in communication with the atmosphere by way of port 9, slide valve 10, and ex- 
haust port II. Piston 8^ is also to the right, and B end of cylinder i is in com- 
munication with main supply 12, by way of slide valve 10^ and port 9\ In order 
to reverse the switch, pressure in controlling pipe 4 must be increased, and as the 
increase takes place more rapidly than air can flow through equalizing port 7, 
piston 8 is moved to the left, taking slide valve 10 with it, thereby admitting air 
at 80 lbs. pressure from main supply 12 to F end of cylinder i ; at the same time 
pressure in controlling pipe 4^ must be reduced, and as the reduction takes place 




RESERVOIRS AND VALVES. 



more rapidly than air can pass through equalizing port f, piston 8^ is moved to 
the left, valve 10* is carried with it, and air is exhausted from B end of cylinder 
I; and switch goes over. Reservoirs 6 and 6^ are added to increase the capacity 
of chests 5 and 5^ respectively. The minimum pressure in controlling pipes is 70 
lbs., the maximum pressure 80 lbs. 

To the frame of interlocking table in tower is attached a switch controlling 
valve 13, view of which is shown at Fig. 389. Port 4 is connected to controlling 
pipe 4„ and port 4^ to controlling pipe 4^ of Fig. 385. Ports 15 and 16 are each 
connected to a cast iron reducing reservoir located at some suitable point in 
tower; port 17 is the exhaust. With operating lever 18 in its normal position, 
slide valve 14 takes the position as shown in drawing, and air from main supply 



956 



USE. 



19 flows into controlling pipe ^. Controlling pipe 4 is in communication with 
reducing reservoir 15 ; reservoir 16 is in communication with the atmosphere by 
way of exhaust port 17. When it is desired to reverse the switch, valve 14 is 
moved upward, thereby closing communication between body of chest and con- 




II 



FIG. 389 — SECTION OF INTERLOCKING TABLE. 



trolling pipe 4^ and reducing reservoir 16 and as all of the air has been exhausted 
out of reservoir 16, air from controlling pipe 4^ flows into this reservoir, thus 
reducing the pressure in controlling pipe 4' ; at the same time valve 14 uncovers 
port 4, and pressure in controlling pipe 4 is increased to 80 lbs. ; reservoir 15 is 



USE. 



957 



also put in communication with the atmosphere, thus exhausting the air out of 
said reservoir. The reservoirs should be of such size as to reduce the pressure 
in the controlling pipes about lo lbs. when communication is established between 
them. 

In order to accomplish the interlocking, it must be so arranged that lever 
i8 and its tappet 19 must make but one-half of their stroke unless the switch has 
properly responded, therefore, slide valve 14 must be shifted its full throw during 
the first half of the stroke of lever 18, said lever to have a silent movement in 
passing from its C to its E position, at least so far as slide valve 14 is concerned. 
To the upped end of valve stem 13^ is secured piece 20, When it is desired to 
reverse switch, latch lever 18^ is brought up against lever 18, thus raising latch 
21 out of notch in quadrant and putting latch 22 in engagement with lower part 
of projection on 20. After valve 14 has traveled its full throw, it strikes against 
stop in chest, thus preventing lever 18 from going further than its C position; 
latch lever 18^ is then released and latch 22 is disengaged from 20, after which 
lever may be taken to its E position, if switch responds properly. When it is 
desired to put the switch back to its normal position, latch 22 is brought into 




FIG. 391. 



FIG. 390. 



lb: 



W^ 




FIG. 392. 
SWITCH APPARATUS — INDICATION CHEST. 



engagement with top of projection on 20; valve 14 is shifted to its normal posi- 
tion, thus reducing pressure in controlling pipe 4 and increasing pressure in con- 
trolling pipe 4\ • Valve 14 is moved its full throw by the time lever 18 reaches its 
C position. Latch 18^ is now released and lever may be brought to its D or 
normal position, provided switch has properly responded. 

SWITCH INDICATION. 

As it is of utmost importance that there be no question as to whether a 
switch responds properly or not, two indication pipes are used, it being impossible 
to get the proper indication with one pipe, for at one move or the other the 
indication would have to be gotten by reduction of pressure, and as this reduction 
might be the result of a leak, a false indication would be gotten. With two indi- 
cation pipes, in one of which the pressure must be reduced and the pressure in 
the other increased in order to give the indication and release the lever, a false 
indication cannot be gotten. At Figs. 390 and 393 is shown the apparatus at 
switch for giving indications. The switch and lock movement has 8 inches stroke, 
whereas the switch points have only 4 inches, therefore bar 24, Fig. 393, moves 2 
inches before the points begin to move and 2 inches after the points are up. To 



958 



USE. 



bar 24, which is coupled direct to piston rod 2, is bolted arm 25. Through the 
outer end of the arm passes valve stem 26, the stem being provided with adjust- 
able knockers 27 and 2.f. With switch in its normal position, slide valve 29, Fig. 
390, takes the position shown; chest 28 is supplied with air at 80 lbs. pressure 
through connection 30, and as indication pipe 31, leading from switch to tower, 
is in communication with body of chest, it contains air at 80 lbs. pressure. Indi- 
cation pipe 31^ being in communication with reducing reservoir 32\ contains air at 
70 lbs. Port 2>Z is exhaust. Attached to the locking table in the tower (see Fig. 389) 
are two valves, 34 and 35, and tappet locking device 39. With switch in its normal 
position, indication pipe 31, valve 34 and reservoir 34^ contain air at 80 lbs. pres- 
sure, and slide valve 36 has established communication between main supply and 
lower end of cylinder 39, forcing its piston upward. Indication pipe 3i\ valve 35 
and reservoir 35^ contain air at 70 lbs. pressure, and slide valve 36^ has exhausted 




FIG. 393 — SWITCH AND LOCKING APPARATUS. 



air from upper end of cylinder 39. Rod 41 is so connected to piston rod 40 that 
when 40 moves downward, 41 moves upward, and vice-versa. 

Fig. 394 shows relative position of tappet and locking pins with tappet, 
lever and switch in their normal position. 

Fig. 395 shows relative position of tappet and locking pins with lever and 
tappet in their C position, should switch fail to respond. 

Fig. 396 shows relative position of tappet and locking pins in their C posi- 
tion, if switch responds properly and lever free to be moved to its E position. 

Fig. 397 shows relative position of tappet and locking pins with tappet, 
lever and switch in their reversed position. It will be noted that pin 41 is ready j 
to stop tappet at half-stroke should switch fail to respond when lever is brought \ 
from its E to its C position. 

Should lever 18 be brought from its D to its C position and switch fail to 
respond, it would be impossible to complete the stroke of the lever or its tappet 
1 9, as edge 42^ of slot 42, Figs. 394, 395, 396 and 397, would be brought up against 
piston rod or pin 40. If switch responded properly, arm 25, Fig. 393, would strike 
knocker 271, valve 29, Fig. 390, would be forced to the left, indication pipe 31 
would be put in communication with reducing reservoir 32, and pressure reduced 



USE. 959 

to 70 lbs.; indication pipe 31* would be put in communication with body of chest 
28, pressure would be increased to 80 lbs., and air would be exhausted out of 
reservoir 32^ through exhaust port 33. A reduction of pressure in pipe 31 would 
cause piston of valve 34 to move downward, and slide valve 36 would exhaust 
air from bottom end of cylinder 39, an increase of pressure in indication pipe 31^ 
would move piston of valve 35 upward, and slide valve 36 would admit air into 
upper end of cylinder 39, thus lowering pin 40, Figs. 389, 394 and 395, out of en- 
gagement with notch 42 and raise pin 41 into notch 43 on opposite side of tappet 
19 (see Figs. 396 and 397). The lever can now be put in its reversed or E posi- 
tion. With locking pins in position shown at Fig. 397, pin 41 is ready to stop 
tappet at half-stroke should switch fail to respond when lever is brought from 
its E to its C position. 

It might be well to add just here that, to interlock the levers of the ma- 
chine, the beveled type of locking is used ; hence, if lever cannot be fully reversed, 
it locks all levers with which it is interlocked. 

Reservoirs 34^ and 35^ are used to increase capacity of valves 34 and 35 
respectively. 

TWO-POSITION SIGNALS. 

Fig. 398 is general arrangement of parts on mast. 

Fig. 399 is indication chest. 

Fig. 400 is vertical section of signal valve and cylinder. 

Fig. 401 is cross section of signal valve, cylinder and reservoir. 

Fig. 402 is top view of valve seat. 

With signal in its normal position, controlling pipe i, chest 2 and reservoir 
3 (see Fig. 401), contain air at 70 lbs. pressure, the equalization between control- 
ing pipe and chest having taken place by means of equalizing port 5, and the 
equalization between chest 2 and reservoir 3 having taken place through ports 6, 
Fig. 402 ; piston 7 and slide valve 8 are to the left, air is exhausted out of operat- 
ing cylinder 9, and counterweight 10, Fig. 398, has brought blade to its horizontal 
or danger position. To put signal to safety, pressure must be increased in con- 
trolling pipe I, and as the increase takes place more rapidly on the controlling 
pipe side of piston 7 than it does on the opposite side of said piston, piston is 
forced to the right, carrying with it slide valve 8; exhaust port 11 is closed; air 
from main supply 12 is admitted by way of port 13 to operating cylinder 9, and 
blade is brought to its vertical or safety position. Reservoir 3 is added to 
increase capacity of chest 2. 

Signal controlling valve 16 (see Fig. 403) is bolted to frame of locking 
table ; i is controlling pipe leading from tower to signal ; 25 is port leading to 
reducing reservoir 25\ 26 is exhaust. With valve 17 in the position shown, con- 
trolling pipe I is in communication vith reducing reservoir 25^, and pressure in 
controlling pipe is at 70 lbs. To put signal to safety, valve 17 is brought to its 
highest position and air at 80 lbs., pressure flows from body of signal controlling 
valve 16 into the controlling pipe, thus increasing the pressure, and, as heretofore 
explained, signal goes to safety. To restore signal to danger it is only necessary 
to put valve 17 in the position shown at Fig. 403, thereby establishing communi- 
cation between controlling pipe i and reducing reservoir 25*, air flowing into this 



96o USE. 

reservoir reducing the pressure in controlling pipe ; piston 7, Fig. 400, is shifted to 
the left, carrying its slide valve with it, thus exhausting the air out of working 
cylinder, and counterweight takes signal to danger. 

SIGNAL INDICATION. 

Assuming that it is more important to know that a signal resumes its 
danger position than it is to know that it goes to safety, the indication for signals 
has been arranged so that an increase of pressure must take place in the indica- 
tion pipe before the lever operating the signal can be brought near enough to its 
normal position to unlock conflicting levers. 

Valve 27, Fig. 399, controls the pressure in the indication pipe 28, leading 
to tower; 29 is main supply; 31 is exhaust; 30 is port leading to reducing reser- 
voir 3o\ located at foot of mast. With signal in its normal position, indication 
pipe 28 is in communication with main supply, hence contains air at maximum 
pressure. Controlling pipe 28 is connected with indication valve 32 in tower (see 



[^-V^T^ [— 



^ 






Q-0 «0 

ii-^ ^^ ^ >JL 

IT 



FIG. 394. FIG. 396 



p^ ^ " i r^'v^ " 



I |*r i \l 



FIG. 395. FIG. 397- 

POSITION OF TAPPET AND LOCKING PINS. 

Fig. 403) ; 3S i^ connection to reservoir for increasing the capacity of chest 32; 
34 is main supply ; 35 leads to upper end of cylinder 37 ; 36 is exhaust. 

Fig. 404 shows relative position of tappet and locking pins with tappet, 
lever and signal in their normal position. 

Fig. 405 shows relative position of tappet and locking pins with lever and 
tappet in their C position should signal fail to go from danger to safety. 

Fig. 406 shows relative position of tappet and locking pins with tappet and 
lever in their C position and free to be moved to their E position, signal having 
gone from danger to safety. 

Fig. 407 shows relative position of tappet and locking pins with lever and 
tappet in their reversed position and signal at safety. It will be noted that pin 40 
is ready to stop lever at its C position as it is being moved from E towards D if 
signal does not go to danger. 

As heretofore stated, indication pipe 28 contains air at 80 lbs. pressure 
when signal is at danger; chest 32 and reservoir 331 also contain air at 80 lbs. 
pressure. Under these conditions piston 32^ of valve 32 is in its highest position, 
and air from main supply 34 is admitted into upper end of cylinder 37, forcing 



USE. 



961 



locking pin 40 down and locking pin 41 up. When lever 18 is brought to its C 
position, valve 17 has moved its full stroke; said valve is then dropped, and if 
signal responds properly, slide valve 271, Fig. 399, reduces the pressure in indica- 
tion pipe 28 by establishing communication between said indication pipe and 
reducing reservoir 30^, Fig. 398, piston ;i2^ of valve 32, Fig. 403, is actuated, air is 
exhausted out of upper end of cylinder 27, and spring 38 forces locking pin 41 
down out of engagement with slot 43, and locking pin 40 up and into engage- 
ment with slot 42 (see Fig. 406), and lever and its tappet is now free to move to 
its E position. Should signal fail to respond properly, pressure in indication pipe 




FIG. 399- 



SEMAPHORE OPERATING PARTS. 



28 would not be reduced, air would not be exhausted out of cylinder 37, locking 
pin 41 would not be withdrawn from slot 43, and lever 18 could not be moved 
beyond its C position (see Fig. 405). If after lever is brought from its E to its C 
position, signal should fail to go to danger valve 27^ Fig. 399, would not be 
shifted, pressure in indication pipe 28 would not be increased, equalizing piston 
32^ of valve 32 would not be actuated, upper end of cylinder 37 would not be 
charged with air, pin 40 would not be withdrawn from slot 42, Fig. 406, and lever 
18 and its tappet could not be moved beyond its C position, and all conflicting 
levers would remain locked. 



962 



USE. 



THREE-POSITION SIGNAL. 

With lever and controlling valve in their normal positions, controlling pipe 
I, which leads to equalizing valve operating the signal from its danger to its 
caution position, and port 4, which leads to equalizing valve operating signal from 




FIG. 402. 



SIGNAL VALVE AND CYLINDER. 



its caution to its safety position are in communication with reservoirs connected 
to ports 2 and 5 respectively, and contain air at 70 lbs. pressure, any leaks in the 
pipes being supplied by ports 39 and 39\ 

To bring signal from its danger to its caution position, valves 17 and 17* 
are moved a half stroke and air at 80 lbs. pressure passes from body of chest, 



USE. 



963 



irough port 18 in slide valve 17 to controlling pipe i, equalizing piston on mast 

actuated and signal goes to its caution position ; at the same time ports 2 and 3 

are put in communication and air is exhausted out of the reducing reservoir of 

;ontrolling pipe i. If it is desired to give a caution position, latch lever i8\ Fig. 

)3, is released, and lever 18 is carried to its reversed position, in order to get the 




FIG. 403 — SIGNAL CONTROLLING VALVE. 



necessary locking. This cannot be done, however, until the proper indication is 
gotten, showing that the signal has reached its caution position. If it is desired 
to give a safety signal, latch lever 18^ is not released, but after indication is 
gotten, showing that signal has reached its caution position, slide valve 17 and 17^ 
are moved the remainder of their stroke, and air at 80 lbs, pressure from body of 
chest passes into port 4 and from thence to equalizing valve which operates the 



964 USE. 

signal from its caution to its safety position ; at the same time ports 5 and 6 are 
put in communication and air is exhausted out of reducing reservoir of con- 
trolling pipe 4 into the atmosphere through exhaust port 6. 

The equalizing valves, reservoirs and operating cylinders on the mast are 
duplicates of those used for operating two-position signals, but are coupled as 
shown, in order that both cylinders can be used in manipulating the blade. 

PNEUMATIC SELECTOR. 

A pneumatic selector is provided by adding slide valve 44 to indication 
chest (see Fig. 390). The controlling pipe from tower runs to an equalizing 
valve similar to signal equalizing valve No. 2, Fig. 400, this valve being fastened 
by means of a bracket to valve 28, Fig. 390. Port 13 of the equalizing valve leads 
to port 45, Fig. 390. With switch in its normal position, main supply would pass 
through port 13 of equalizing valve 13 ; thence to port 45 of selector slide valve ; 
thence by way of port 46 of selector slide valve to the cylinder of one signal. If 
switch was in its reverse position, main supply from port 13 of equalizing valve 
would go to cylinder of the second signal by way of ports 45 and 47 of slide 
valve 44, Fig. 390. 

Where selectors are used, one signal equalizing valve handles two or more 
signals. 

PNEUMATIC SLOTS. 

A pneumatic slot is provided by running the controlling pipe from one 
tower to the back of the controlling valve of a second tower, and introducing a 
check to properly control the current of air. A leak in this check does not afifect 
the working of the slot, from the fact that a leaky check valve will not allow 
the increase and reduction of pressure to take place fast enough to operate the 
equalizing signal valve. 

LOCKING DOGS. 

Switches and signals must respond properly before levers operating them 
can be fully reversed. It is obvious that lever can be brought from its D to its 
C position, which, as heretofore explained, should operate the switch or signal, 
and that, while the switch or signal is moving, the lever can be returned to its 
E or D position. Take signal lever for example : When lever is brought from 
its D to its C position, signal should go to safety. Now, while the increase of 
pressure is taking place in the controlling pipe, signal is moving from danger to 
safety, and the decrease of pressure is taking place in indication pipe; there is 
nothing to prevent lever being returned to its D position, the locking pin striking 
the bottom of the tappet. Signal lever and its tappet would then be in their 
normal or danger position and the signal at safety. To obviate this, it must be 
so arranged that after a lever has been started from its normal or reversed posi- 
tion, it cannot be returned to either of these positions again until it has made full 
stroke backward or forward, as the case may be. To this end, pawl and ratchet 
arrangement shown at Fig. 408 is used. 

K-L is slot in side of quadrant M; i is pin passing through and secured 
to lever; pawl N is pivoted to outer end of pin i and engages with ratchet Q. 
The lower end of pawl N is pivoted to rod P ; rod P has spring P\ Rod P 
engages with eye bolt, the bolt being fastened to quadrant. As lever is being 



USE. 



9^5 



carried from its D to its C position, that part of pawl marked N^ engages with 
teeth in ratchet Q. If after lever is started from its normal position, any effort 
is made to return the lever to its normal position before it is carried to its E or 
reversed position, N^ engages with the teeth and prevents the movement. When 
lever reaches about three-quarter stroke, pawl N strikes pin R\ the position of 
pawl is reversed, and that part of pawl N" engages with the teeth in the ratchet 
and will prevent lever after having been once moved from its E or reversed posi- 
tion, being returned to that position until it has moved to its D position. 

LEAKAGE. 

As it is almost a matter of impossibility to keep the pipe lines perfectly 
tight, a system of feed ports have been introduced whereby the low pressure pipes 
are supplied with air at minimum pressure — that is, 70 lbs. As signals are kept 
at danger except when they are lowered to permit a train to pass, and as when 
signals are at danger the indication pipes are in direct communication with the 



pA 



/w 



' ■ rt ' ^ 



ro 



40 
FIG. 404. 



\^ 



FIG. 406. 



r^ 



■^ 



90 



r l]\ I 1 : 



rV 



-^ 

^c^ 



40 
FIG. 405. 
POSITION OF TAPPET AND LOCKING PINS. 



[[*' I \90 
FIG. 407. 



main supply, and as the indication pipes are only cut off from the main supply 
when the signals are at caution or safety, it has not been found necessary to 
arrange to take care of the leakage in the signal indication pipes. See ports 23 
and 231, Fig. 389; 34 and 34^ Fig. 390; 39, Fig. 403. Without some method of 
providing against leakage the switch or signal could be gotten over the first time 
almost as quickly as though the pipes contained normal pressure, but we would 
have to wait until the pressure behind the equalizing pistons reached something 
over 70 lbs., before switch or signal could be moved again. 

SIMPLICITY. 

As will be seen from the foregoing explanation, there is no delicate or 
complicated mechanism to get out of order, and that the apparatus does not re- 
quire delicate adjustment. Springs perform no important function. If thought 
advisable, those on the signal indication pins can be discarded and weighted levers 
substituted; but as they are made amply strong, are in full view, and can there- 
fore be easily inspected, there is no reason why they should give rise to trouble. 



966 



USE. 



Absence of electric and hydraulic apparatus contributes largely to the simplicity 
of the system. 



SAFETY. 



The pressure must be increased or decreased suddenly, otherwise the equal- 
izing piston will not be actuated. A reduction or increase of pressure caused by 
a leaky slide valve will not actuate these pistons. To demonstrate this, one of 
each of the slide valves was made to leak very badly, the leak being very much 
greater than if valve was permitted to run for years without attention. In each 




FIG. 408 — PAWL AND RATCHET ARRANGEMENT. 

instance the increase or reduction of pressure caused by such leaks failed to 
actuate the equalizing pistons. 

Should the high pressure controlling pipe of a switch, or a switch indica- 
tion, spring a leak, and the pumps or compressors be unable to maintain the 
pressure against such leak, the switch will not fly over, nor will a false indication 
be given, for in order to get switch over or to get an indication, a sudden increase 
of pressure must be had in the low pressure pipe. Should the controlling pipe of 
a signal spring a leak, and the pumps or compressors be unable to maintain pres- 
sure against such leak, the signal will go to danger. It will be remembered that 
it is necessary to increase the pressure in the signal indication pipe to get tappet 
unlocked so as to put lever in its normal position. 



■Ml 



USE. 



967 



An experimental plant consisting of 8 levers, handling 

2 Switches, 

I Cross-over, and 

7 Signals, was put into operation Dec. ist, 1894. Three-quarter inch 
IS pipe was used for controlling and indication pipes. No effort was made to 
^protect the pipe lines, most of them being laid on the surface of the ground. 
With the thermometer at 10° below zero, no trouble was experienced with ice 
closing up the ports or passages, or causing the equalizing pistons to stick. A 
careful search was made, but not the slightest particle of ice could be found in 
l^ny of the valves or passages. With the yard flooded with water to the tops of 
*the ties, the switches and signals responded without interruption. Two 9%" 
Westinghouse pumps were used to compress the air for this plant. A %" cock 




FIG. 394 — CONTROLLING VALVE, 3-PISTON SIGNAL. 

was left wide open on a pipe line of a signal i,ooo feet away and even with this 
leak, the signal and its indication responded promptly. 

Below is given the time consumed in operating the switches and signals, 
including indications for same, this record having been taken from the switches 
and signals comprising the experimental plant: 

SWITCH. 

100 feet away 0.8 seconds. 

250 " 1.05 

500 " 1.75 " 

750 " 2.5 

1,000 " 31 " 

SIGNALS. 

TOO feet away 1.25 seconds (high; 



300 

350 

500 

1,000 

1,500 

2,000 



.1.1 

.1.34 

.1.91 

■3.07 

.4.00 

.5.56 



(dwarf) 
(high) 



968 ' USE. 

It is not necessary to wait for pressure to equalize. By actual test, a 
switch was handled as follows : 

oeo feet away 28 times per minute. 

300 " • 20 

A signal was handled as follows : 

300 feet away 28 times per minute. 

1,000 '' ' 20 " '' 



HANDLING SWITCHES AND SIGNALS. 

The Nashville, Chattanooga & St. Louis Railway has six interlocking 
towers between the Union Passenger Statiop at Nashville and its shops, two 
miles distant, equipped with the pneumatic system of handling railway switches 
and signals, as devised by Mr. J. W. Thomas, Jr., and described in our October 
(1897) issue, page 954. These plants have 176 working levers, handling— 
35 Switches, 
19 Cross-overs, 
4 Derails, 
123 Signals, and 
9 Crossing gates. 
There is in use — 

3>4 miles of 3" main, 
2 miles of 2" supplemental main, and 

2,7 miles of ^" pipe; the M'' pipe being used for operating the switches 
and signals, and getting indications from same. 

Each tower is a block station, and we give below a statement of the trains 
handled between Union Passenger Station at Nashville and the Centennial 
Grounds, the railway terminal station being opposite their shops, for the six 
months ending October 31st, 1897: 

TABLE 74 — STATEMENT OF TRAINS HANDLED BETWEEN NASHVILLE AND SHOPS — 1897. 





No. OP Trains. 


Av'ge per Day. 


Av. PER W'rk Day. 


Highest Any Day. 


Month. 


Single 
Track. 


Double 
Track. 


Single 
Track. 


Double 
Track. 


Single 
Track. 


Double 
Track. 


Single 
Track. 


Double 
Track. 


May 


7,136 
7,356 
7,431 
7,357 
7,306 
7,599 


6,639 
6,892 
7,357 
6,942 
6,839 
7,106 


230.2 

245 

239.7 

237.3 

243.5 

245.1 


214.2 
229.7 
234.9 
223 9 
227.9 
229.2 


253.3 
266.5 
259.7 
260.5 
262.5 
269.5 


230.3 

247.2 
25.'). 5 
247.5 
243.5 
253.4 


284 
292 
278 
273. 
274 
314 


263 


June 

July 


280 
275 


August 

Hepteniber 

October 


257 
260 

306 


Total, 6 months.. 


44,179 


41,775 














Ave. per month . . 


7,363 


6,962 


240.1 


226.6 


262 


246.2 







USE. 



969 



These trains were handled by signals, no train orders having been issued. 
Notwithstanding the fact that the system was entirely new, was put up hurriedly, 
and the signalmen had very little previous training in interlocking work, the traffic 
was handled without accident, the maximum delay to any. train being six minutes. 

Length of section of single track Yz mile. 

Length of double track 1^/2 miles. 

481,525 passengers were handled between the Union Passenger Station and 
the Centennial Grounds, none of whom received the slightest injury. 



THE LYMAN PNEUMATIC CROSSING SIGNAL. 

The Lyman Pneumatic Signal Company, of New York City, is now bring- 
ing out its patent air compressor or pump, track instruments and other necessary 





FIG. 409 — LYMAN AUTOMATIC AIR-COMPRESSOR. 



devices for ringing a highway crossing bell by means of compressed air, and it is 
announced that one of the bells has been in use for several years on the Delaware, 
Lackawanna & Western, at Sherburne, N. Y. The bell or gong is rung by an 
electro magnet in the usual way. The battery and wires are all within the signal 
box, and the electric circuit is closed by the piston of an air cylinder, which is 
moved by an air impulse transmitted through an underground pipe from the 
compressor, located at the distant point. The compressor is actuated by the 
wheels of passing trains. The amount of pressure required is so small and the 
adjustment of the apparatus is so sensitive that eight wheel contacts are more 
than sufficient to set the bell ringing; in other words, an engine and tender alone 
will furnish ample power to compress the necessary quantity of air. 



970 



USE. 



The principal parts of this signal are shown in the accompanying drawings. 
Fig. 409 represents the compressor and track instrument, and Fig. 410 4s a per- 
spective of the same. The pump shown in Fig. 410 is the one which has been in 
service four years at Sherburne. The latest pattern is somewhat different in 
some of its details, it being found unnecessary to have so high a cylinder. Fig. 

411 shows the arrangement of cylinders in the signal box at the crossing and Fig. 

412 shows the connections to these cylinders and to the bell. 

Referring now to Fig. 411, N is the cylinder by which a train from the 
north sets the bell ringing, and S is actuated by trains coming from the south. The 
function of cylinder C is to stop the ringing of the bell, and its piston is moved 




FIG. 410 — LYMAN AIR-COMPRESSOR FOR HIGHWAY CROSSING SIGNAL 



by a pump fixed close to the crossing. On single track it is of course actuated by 
trains in either direction. 

An impulse of air coming through n lifts the piston in N and, by means of 
lod 3, closes the electric circuit which rings the bell. The bell rings as long as 
the piston of N remains up and this time is governed not only by the length of 
the train that sends the air impulse, but also by the fit of the piston and the size 
of the air-escape, which can be adjusted for any desired length of time. When 
the piston in C is lifted it forces air into the upper ends of N and S and at the 
same time lifts pins i and 2, by which valves a and b are opened, exhausting the 
pressure in the lower ends of the upper cylinders. The reference letters N, C 
and S in Fig. 412 have the same general meaning as the same letters in Fig. 411. 

The pump (Figs. 409 and 410) was designated so as to give a piston stroke 
of four inches, but experience showed that with a piston 10 in. in diameter a 
stroke of ^ in. is sufficient, and in the new design the cylinder is made much 



USE. 



971 



shorter. As before stated, the shortest possible train furnishes all necessary 
power to close the bell circuit. Relief valves are provided where necessary to 
prevent excessive pressure in cylinders. 

The track level or bar A (Fig. 409) is designated for use on a single track 
road, being so adjusted that trains going in one direction have no effect on the 
pump. The inclined position of this lever is best shown in the perspective, Fig. 




jn 1 


m 


L-m 


C 






n 


UJ 



^ 



FIG. 411 — CYLINDERS FOR PNEUMATIC HIGHWAY CROSSING SIGNAL. 



410. The wheels of a train running from right to left (Fig. 410) press against 
the bar and push it forward, revolving the shaft B (see Fig. 409) and lifting the 
plate C. A train running from left ^o right pushes bar A into the slot in S, leav- 
ing S and B motionless. 

The signal at Sherburne is in constant use and the officers of the railroad 
company give a good account of it. It is, of course, unaffected by lightning or 
stray electric currents. 

The inventors of this signal have also patented apparatus by which a track 
instrument and a pump of the kind shown can be used to automatically close and 



972 



USE. 



open a highway crossing gate ; and to make the use of an automatic gate feasible 
they use an ingenious ball and socket joint, so that if the gate, in coming down, 
should strike a man or a horse the blow would be harmless. This is accomplished 
by making the outer end of the arm (the end farthest from the standard and 
nearest the center of the street) very light, and joining it to the heavier portion 
by a joint so controlled by springs that the arm would yield on slight pressure 
and would move upward or outward. In case a pedestrian or a teamster should 
be caught between closed gates he would naturally try to escape, and if he should 
press through the gate the arm would yield without breaking. On both single 







J 



FIG. 412 — CONNECTIONS FOR PNEUMATIC CROSSING SIGNAL. 

track and double track lines the gates are so arranged that if a train moving 
away from the crossing actuates the cylinder to open the gates, while a second 
train is approaching, the latter train holds the gates closed. 

A large model of this signal, and also one of an automatic crossing gate, 
with a miniature locomotive to set the apparatus in operation, is now on exhibition 
at the company's headquarters, 80 and 82 Fourth avenue, New York City. There 
IS also shown in the model the necessary apparatus to work an automatic block 
signal system on the same principle employed in the other devices.— Railroad 
Gazette. 



PNEUMATIC INTERLOCKING. 

It has been the custom for many years to operate the switches and signals 
of large and important track systems from a central point, in order that greater 
economy and efficiency in train service might be secured than was possible under 
the primitive method originally employed, which entailed the use of many men 
moving continuously from switch to switch, and a diversity of hand signals and 
targets that, to say the least, were confusing and oftentimes misleading to engine- 



USE. 



973 



In concentrating the operation of switches and signals, an important ad- 
junct to their safe operation, heretofore impracticable, became possible; switch 
and signal levers were readily made to interlock one with another so that a 
signal could be given for a train to proceed over a given route only after all 
switches in it were securely set and locked for the safe transit of the train over 
them. Conversely, a signal giving a train right of way over a route, locked 
against operation all switches in it until the signal was withdrawn. This method 
of operating switches and signals is known in railroad vernacular as an "Inter- 




FIG. 413 — BOSTON SOUTHERN STATION — WESTINGHOUSE INTERLOCKING SYSTEM DUR- 
ING FEBRUARY (1899) STORM. 



locking." The apparatus *by which they are moved is termed an "Interlocking 
Machine," and the structure in which it is located, an "Interlocking Tower." 

The levers of an interlocking machine are usually mounted in a cast iron 
frame secured to the framework of a tower, and are massive affairs connected 
with the switches by one-inch pipe lines, which are moved longitudinally by the 
levers in suitable guide rollers or pipe carriers arranged to support them at short 
* intervals upon suitable foundations, carefully set as to alignment. Signals are 
likewise operated, frequently, but more generally by means of heavy iron wires 
suitably supported in anti-friction carriers upon stakes or iron straps extending 
from the pipe line supports. 



974 



USE. 



However carefully applied and however well designed the appliances of 
such a system, it is found entirely impossible to operate from a single lever, in 
large plants, all of the devices that are permissible of such operation, owing to the 
excessive load they would present to the operator if thus connected. It, therefore, 
is customary to perform by the operation of two, three, four, and occasionally five 
levers the work that could be performed by a single one were the operator's power 
unlimited. When this fact confronted the man who virtually made the hand brake 





FIG. 414— PNEUMATIC SIGNAL SHOWING OPERATING CONNECTIONS. 



a "5th wheel" on passenger coaches, by adapting compressed air, in the hands of 
one man, to the duties formerly performed by the muscular energy of several, it is 
not surprising that his attention was turned toward relieving the labor and ex- 
pediting the manipulations performed in interlocking towers. 

With the experience that brought the air brake to its present state of per- 
fection as an encouragement to the undertaking, the development of the Pneu- 
matic Interlocking System was begun by Mr. George Westinghouse, Jr., in 1881, 
as president of The Union Switch & Signal Co. of Pittsburg, Pa. 



USE. 975 

After years of laborious and costly experiments, and notwithstanding a 
very general distrust of the system during its experimental stages, its develop- 
ment was carried through successfully, and to-day it is the system employed at the 
leading terminal stations in this country and at many minor places. Its introduc- 
tion at the new Southern Station in Boston has been attracting widespread in- 
terest at home and abroad, chiefly because of the magnitude of the station itself, 
but largely because of the great area and facilities of its track system and of the 
complexity of the interlocking necessary to handle it. The tracks included in the 
interlocking system contain 31 double slip switches, 31 pairs of movable frogs and 
52 turnouts — the equivalent of 238 ordinary switches. Eleven trains may move 
simultaneously into or out of the train shed ; 148 semaphore signals are provided 
for the 400 possible routes presented in the switch system. 

Each switch and signal is connected directly to the piston of a pneumatic 
cylinder secured to its support ; each cylinder is provided with a valve controlling 
the admission and discharge of air to and from it. These valves are shifted by 
electro-magnets under the control of the interlocking machine which consists of 
diminutive levers each arranged to rotate a shaft through an angle of 60 degrees 
when operated, and to thereby shift electric contacts arranged thereon so as to 
produce the desired conditions of the valve magnets (to which they connect) and 
consequently the desired movements of the switches and signals. 

These shafts are also adai)ted to move bars lying at right angles to and 
above them, which extend from end to end of the machine, and which by a system 
of "cross locks" are made to interlock one with another in the manner customary 
in other and earlier types of interlocking machines. The extremities of these 
shafts are engaged by the armatures of electro-magnets which are controlled by 
the switches or signals operated, and which are so actuated and controlled by the 
latter that the levers and the devices operated by them must coincide in position 
before a clear route can be produced. 

A minature model of the track plan is mounted vertically upon the machine 
frame, the switches of which move to correspond with those in the yard as the 
levers are operated, and give at all times a correct representation of the track 
connections. 

The signals are mounted generally upon iron truss bridges, 9 of which are 
used for their- support at the new station. They are of what is termed the "Sema- 
phore" type, consisting of an arm or blade pivoted to a post and extending to 
the right as viewed by enginemen approaching it. When horizontal this arm 
signifies danger and is so held by a heavy counterweight normally. When de- 
clined 60 degrees from the horizontal it signifies safety and is thus moved, in this 
system, by action of the compressed air upon the piston of its operating cylinder. 
This arm carries two colored glasses: a red one before a lamp at night is dis- 
played when at danger and a green one when at safety. From Fig. X a better 
understanding of this device may be had. The electro-magnet M is in direct con- 
trol of the interlocking machine. When de-energized its armature is held from 
the ipagnet by the spring S and the action of the compressed air upon the valve 
stem E, formed by the rod extending from the armature into the valve chamber. 
The pin valve P is likewise held seated by the same forces, shutting off the escape 
of the air from chamber C to chamber C, the latter being normally connected 



976 



USE. 



through the open valve E with the atmosphere, as is also the signal cylinder port 
S P. 

When the magnet is energized the valve stem E is depressed closing the 
exhaust port E P and opening the pin valve P so that the pressure is permitted to 
enter chamber C and consequently the cylinder of the signal, the effect of which 
is to cause the piston to be depressed and the signal operating rod to be elevated, 




FIG. 415- 



rOMPRESSORS IN POWER HOUSE. 



with the result that the counterweighted end of the signal is likewise elevated and 
the blade lowered to safety. 

When the magnet is de-energized the valves assume their normal positions 
and the air escapes from the signal cylinder, the signal moving by gravity back to 
danger. 

The switch cylinders are double acting and therefore require two such 
magnetic valves, one controlling the presure at one end of the cylinder and one at 
the other. 

Owing to the large volume of air used in the larger cylinders of the 
switches, these magnetic pin valves do not give direct admission and discharge of 
the air to and from the cylinders, but control small auxiliary cylinders which 
shift a D-valve capable of more readily controlling the pressure to and from the 
switch cylinders. 



USE. 



977 



This D-valve is further provided with a plunger which engages it and pre- 
vents its movement unless the plunger is first withdrawn. The withdrawal of this 
plunger is effected by a third magnetic valve and auxiliary cylinder and the three 
magnetic valves are controlled by three separate wires extending from them to 
contacts of the interlocking machine. 

The D-valve lock is a precautionary device entirely and is introduced 
simply to remove as far as possible the likelihood of a false operation of a switch 




FIG. 416 — I'NEUMATIC SWITCH MOVEMENT COVER REMOVED. 



from unusual conditions and from extreme neglect to properly maintain it in 
normal order. 

The switch cylinder operates with an 8-inch stroke a specially designed 
movement which gives motion to the switch during the forepart of its movement 
and locks it in position during the last part of it. It also gives motion during its 
entire stroke to a bar pivotly mounted along the outside of the switch rails that 
is known as a "Detector Bar," and which is designed to prevent the movement of 
a switch under a train passing over it, or standing upon it. This bar rises imme- 
diately above rail level at the beginning of the piston stroke and before the switch 
is moved at all ; a train upon the switch rails prevents the elevation of the bar 
and consequently the movement of the switch. 

Under each switch cylinder is placed a cast iron reservoir directly con- 
nected with the main pressure pipe of the system ; from the reservoir an armored 
hose connection extends upward to the switch valve and forms an elastic medium 



978 



USE. 



through which the valve is supplied with compressed air, thus avoiding all risk of 
injury to the pipe fittings and valves due to change of track alignment, and to the 
vibration of trains passing over the switches operated. 

The compressed air is generated in the company's power house by one or 
the other of two Ingersoll-Sergeant Piston Inlet Compressors of 14 in. diameter 



f r f>.^ 




FIG. 417 — SIGNAL CYLINDER. 



and 18 in. stroke, each capable of pumping 150 cubic feet of free air per minute— 
an amount vastly in excess of that required for the interlocking system, but an 
amount of great value in the event of an emergency that momentarily might ex- 
haust the supply in storage. These compressors are therefore running at their 
minimum speed, about 30 revolutions, instead of at 120 revolutions, their maxi- 
mum speed, — normally. Each compressor discharges the air as compressed into 



USE. 979 

receiving tanks from which it is conducted to a third receiver before passing 
through a system of manifold pipes of large radiating surface for reducing it to 
atmospheric temperature before entering the supply main, and for precipitating 
the moisture contained in the heated air at a point convenient for its removal 
periodically. J. C. Coleman. 



THE USE OF COMPRESSED AIR IN THE FREIGHT YARD OF THE 

LAKE SHORE AND MICHIGAN SOUTHERN RY. AT WEST 

SENECA, N. Y. 

A modern freight yard cannot be considered complete unless it is provided 
with a compressed air plant for testing the brakes on cars when made up into 
trains before departure, and also for use on the repair track, both for testing 
brakes and for facilitating the work of repairs. With such a plant the inspec- 
tors and repair men have compresed air "on tap" at all times and are, therefore, 
not compelled to wait for the locomotive to be attached to the train before it can 
be tested, thus eliminating all delays and having the train ready to leave when the 
engine is attached. 

About three years ago the Lake Shore & Michigan Southern R. R. Co. es- 
tablished at West Seneca, near its eastern terminus, a new freight yard, in which 
a compressed air plant was installed which meets all requirements in this line. 

Compressed air is furnished by a duplex compound air compressor, having 
a capacity of 342 cubic feet of free air per minute. It is located in the machine 
shop near the round house and delivers the air into a storage reservoir of about 
100 cubic feet capacity located outside of the building. This storage tank is 
chiefly for the purpose of equalizing pressure and for collecting moisture, for the 
larger part of the storage capacity of the plant is contained in the 25,000 feet of 
distributing pipes which are laid through the repair and inspection yards and 
bave a volume, approximately 3,000 cubic feet. A safety valve is provided on the 
storage tank, which limits the pressure to 105 pounds per square inch, although a 
regulator on the compressor controls the pressure in such a way that there is 
seldom, if ever, any use for the safety valve. 

The main feed pipe is 2 inches in diameter and is laid on top of the ground, 
Adhere possible, and boxed in, to a point near the yard office, from which branch 
)ipes of lYi inches diameter extend to the repair and inspection yards. 

The repair yard consists of six tracks, in two groups of three each, the 
intire space being planked over level with the top of the rail. Four lines of 1% 
inch pipe are laid through this yard, located midway between the tracks and 
astened to the planking by Y^ inch staples, each group being provided with a cut- 
jut cock, so that it can be shut off for repairs without affecting any of the other 
ines. Connections for attaching hose are provided at every 50 feet, and are made 
.f i-inch Westinghouse hose coupling threaded and screwed into i-inch cut-out 
ocks, and connected to tees in the pipe lines by nipples. These connections are 
Totected from the weather when not in use, by cast iron boxes, which are shown 
n Fig. 418, and will be described later. 



9<So 



USE. 



In the repair yard compressed air is used for testing the brakes on cars, 
and also for raising cars, which is done by means of pneumatic jacks, consisting 
of a case iron cylinder(Fig. 4i9)provided with a piston, the rod of which extends 
through the top head and is provided at its end with a recessed casting which 
bears against the sills of the car when in use. Air is admitted under the piston 
by a ^-inch pipe provided with a cut-out cock ; the inlet port in the lower head 
has in it a small check valve which prevents the air from escaping through the 
inlet pipe should a leak suddenly occur; to lower the piston the air is released by 
a separate pipe and cock. Two jacks are used to a car and they are connected 
to the air supply by hose, joined together by a Y-shaped nipple, so that each jack 
gets the same pressure and the car is raised equally on both sides. Two sizes of 
jacks are in use, lo inches in diameter for light cars, and i8 inches for loaded 
ones. The larger jacks are mounted on wheels to provide an easy means of mov- 




7 ^ J 



^ '( T 

FIG. 418 — ARRANGEMENT OF AIR PIPE FOR TESTING AIR BRAKES. 



ing them from place to place; the smaller ones are light enough to be carried 
around, although trucks are provided which are used when they have to be taken 
any distance. 

Air is also used in the repair yard to drive a pneumatic drill or boring ma- 
chine, and also to furnish blast for the blacksmith forge. 

In the inspection yard there is an air line of i^ inch pipe for every two 
tracks. It is laid on top of the ties, close to the rail and fastened by f^-inch 
staples. Connections similar to those on the repair track are provided ever> lOO 
feet and are enclosed on three sides by a cast iron casing, resting on the tie. the 
top and open end being closed when not in use by a hinged cover and end, which 
is turned out of the way when the test hose is connected. Fig. 418 shows the con- 
ncclion and box and their arrangement on the track. Wedge-shaped pieces of 
timber are fastened on each side of the box on top of the ties, to prevent train- 
men who are walking along the track from stumbling over the obstruction. On 



USE. 



981 



account of the length of the lines in the inspection yard, expansion joints had to 
be provided, which are in the form of U-shaped connections between the ends of 
sections of the pipe 300 feet long, and are made up of a unicn, nipples, elbows, 
hose nipples and short pieces of hose as shown in Fig. 421. These joints are en- 
closed in boxes, protected by wedges, like the regular connection boxes. Each 
separate lihe is provided with a cut-out cock. The pressure of the air is reduced 
by means of a reducing valve to 70 lbs, before it passes into these pipes and the 
testing is done by means of an engineer's valve mounted en a wheel barrow 
and connected to the pipe line and the train by hose. After a train has been 




CHECK VALVE 



FIG. 419 — PNEUMATIC JACK. 



tested the train pipes are left charged, so that when the locomotive is attached no 
time is lost in pumping up the train. 

Another plant at West Seneca, which depends largely upon compressed air, 
but which is separate and independent from that provided for the repair and in- 
spection work, is that for supplying water for the various purposes around the 
yard, and also for elevating sand for use in locomotive sand boxes. 

The water is taken from seven driven wells and also from a creek near by. 
The wells are from 100 to 105 feet deep, and the one in the creek is about 20 feet 
deep. Compressed air, at 60 lbs. pressure, is supplied by a straight line air com- 
pressor, having a capacity of 384 cubic feet of free air per minute, two com- 
pressors being provided to always have one ready in case of emergency. The 
principles of the Pohle air lift are made use of to bring the water to the level of 



982 



USE. 



the yard. The wells are of 6-inch pipe in which a piece of 2^-inch pipe extends 
almost to the bottom and a ^-inch air pipe runs down on the outside and en- 
ters the 2H-inch pipe near its bottom. The escaping air draws the water up 
with it and delivers it through the 2^ -inch pipe into a main, which carries it 
to a large surface well of 100,000 gallons capacity, which is floored and housed 
over and provides a place for the two air compressors and also two water pumps, 
which deliver the water from this well to the storage tank of 100,000 gallons 
capacity, 35 feet above the ground. From this point it is distributed to stand- 
pipes and hydrants at different points of the yard. The water pumps have a ca- 
pacity of 500,000 gallons per day and are also in duplicate. 

Sand for use on locomotives is thoroughly dried by steam and delivered 
by the drier near the floor level of the sand house, and is then blown from there 
to a reservoir on the upper level, from which it flows by gravity to the sand box 
of the locomotives through pipes with flexible joints. The apparatus for elevating 
the same consists of a 2-inch vertical pipe into the lower end of which a ^-inch 




FIG. 421. 



pipe extends, drawn down to a ^-inch nozzle, and when air is allowed to escape 
through this nozzle it draws the sand up with it and deposits it in the reservoir 
on top. 

In the use of this apparatus it was found necessary to get rid of the mois- 
ture in the air by passing it through a chamber where the moisture could pre- 
cipitate and be drawn off by a cock at the bottom. 

The air compressors used in connection with these plants deserve more than 
a passing mention, as by their use a large saving is effected over the cost of oper- 
ating other machines for doing the same work. 

The compressor used in connection with the testing tracks and repair yard 
is a class H, Ingersoll-Sergeant duplex steam driven air compressor with com- 
pound air cylinders (Fig. 420), having lo-inch steam and 16 and lo-inch air cylin- 
ders with a stroke of 10 inches, giving with 150 revolutions a capacity of 342 cubic 
feet of free air per minute. The steam cylinders are provided with plain slide 
valves driven by eccentrics. 

The compressor used in connection with the water supply is a standard type 
made by the same company. 

It still seems to be a mooted question among some railroad mechanical men 
as to what is the most economical machine for compressing air for shop use. 




USE. 



983 



Naturally the first machine used for this purpose at railroad shops was a locomo- 
tive air brake pump, of which there are always some spare ones on hand, and 
these can be used without their cost appearing on the books as a new investment. 
As the uses to which compressed air is put increased more than one pump was 
found to be needed to supply the demand and it was soon found that while there 
was no material outlay chargeable to shop equipment, there was quite a marked 
difference in the consumption of coal in the boilers, and it is now almost uni- 
versally conceded that while the air brake pump is the best machine that can 




FIG. 420 — INGERSOLL-SERGEANT DUPLEX AIR COMPRESSOR — L. S. & M. S. RY. 



be procured when used in its legitimate sphere, i. e., on the locomotive for sup 
plying air to operate the brakes, it is a very wasteful bne when used to furnish 
a large suuply for a shop plant, where floor space and water for cooling purposes 
are readily obtained, and the installation of an air compresser will soon show 
a marked decrease in coal consumption and repairs. Even when the demand foi 
air is not sufficiently large to warrant the purchase of an independent com- 
pressor, one driven by belt by the shop engine will show almost as much economy 
as a steam driven one. 

On the locomotive the air brake pump runs comparatively slow, not pump- 
ing a very large amount of air, as aftei the train is charged it is only necessary 



984 USE. 

to supply what is lost by leakage, excepting after brakes are released, when a few 
strokes of the pump will usually bring the pressure up to the maximum, and the 
repairs therefore are comparatively light. When used, however, to supply the 
large and constant amount of air needed in a shop plant, the wear and tear is con- 
siderable and the pump has to be repaired and many parts renewed at very short 
intervals. 

Some years ago the Westinghouse Air Brake Co. conducted a series of 
tests to ascertain certain data in regard to the air brake pump as compared with 
air compressors, from the results of which tests some figures have been selected 
which are given below : 

The 9^-inch air brake pump compresses about 45 cubic feet of free air 
per minute to 90 lbs. pressure, or 2.5 cubic feet per pound of steam. A two-stage 
compressor, operated by compound non-condensing engine, showed 13.7 cubic feet 
of air per pound of steam. Assuming that the compressor which has been de- 
scribed as supplying air for the repair and testing yard at West Seneca delivered 
on an average 250 cubic feet of air per minute, which is less than 60 per cent, of 
its capacity, and assuming further that on account of having only a simple engine 
instead of compound, the free air compressed was only 10 cubic feet per pound 
of steam, which is probably too low, we would obtain a consumption of 
250 X 60 

= 1,364 lbs. of water per hour, which would require, assuming 8 lbs. of 

II 
water evaporated by the boiler per pound of coal, 170 lbs. of coal per hour. 

To compress the same amount of air by means of 9^ -inch air brake pumps 
would require four or five of these, compressing 2.5 cubic feet per pound of water, 

250 X 60 

which at the same figures as given would require =■ 750 lbs. of coal per 

2.5 X 8 
hour, or 4.4 times as much as required by the compressor. 

Assuming a service of 300 days of 10 hours each per year, with coal at $1.00 
per ton, the cost of fuel would be 170 X 3,000 X $1,00 =$255 for the compressor, 
and 4.4 times as much, or $1,122, for the pumps. The price of coal is taken at a 
minimum figure and the difference in cost will be much more at the price that 
is usually paid. 

The consumption of water would be about as follows: The boiler would 
Iiave to evaporate for the compressor 1,364 lbs. of water per hour, or about 
481,400 gallons per year, for the air brake pumps 6,000 lbs. per hour, or 2,118,000 
gallons per year. The compressor would further require for cooling purposes 
about five gallons per minute, or 900,000 gallons per year, making a total consump- 
tion of 1,381,400 gallons, which at 3 cents per 1,000 gallons is a conservative 
figure, and would amount to $41.44, while the cost of water for the air pumps 
would be $50.82. 

The market price of a compressor of about the size and kind mentioned is 
approximately $1,700, while that of one 9^ inch air pump is $125.00. Allowing 5 
per cent, annually for interest on equipment and 10 per cent, for wear and tear, 
the latter being high for the compressor and low for the pump, and tabulating all 
the above figures we get the following: 




USE. 



985 



r 


First cost. 


Expense for 1 year. 




Fuel. 


Water. Interest. 


Deprecia- 
tion. 


Total. 


1 compressor 

6 air brake pumps 
(93^ in.) 


1700 
750 


255 
1122 


41 
63 


85 
37 


170 
75 


551 
1297 







From which it will be seen that the cost of running the air brake pumps 
would be 2.4 times as much as that of the compressor and the latter would save 
its cost, on runmng expenses alone, in a little over two years, or would almost 
save the difference in first cost during the first 15 months. 

It might be urged that air brake pumps could be used which had previously 
been in service on locomotives and that there would then be no expense for first 
cost. Nevertheless the pumps would have been paid for at some previous time, 
and they represent the investment of a certain amount of money, so that the 
interest and depreciation should still be considered in their running expenses. 
When old pumps are used for shop purposes, it is usually the 8-inch pumps that 
are taken which have been replaced on locomotives by those of larger capacity; 
these may be valued at $100 each, although the cost of a new one .at the present 
time is higher. 

Reverting to the tests referred to as made by the Westinghouse Air Brake 
Co., it was found that an 8-inch pump compressed 1.85 cubic feet of free air pei 
pound of water. It would therefore require, using the same figures as before. 

250 X 60 

= 1,014 lbs. of coal per hour to pump the same amount of air by means 

1.85 X 8 

of 8-inch pumps, or six times as much as required by the compressor, and the cost 
per year woulfi be $1,530. The water consumption of the pumps would be 
2,455,200 gallons per year, costing $73-65- laoulating these figures we have the 
following : 





First cost. 




Expense for 1 year. 






Fnel. 


Water. 


Interest. 


Deprecia- 
tion. 


Total. 


1 compressor 

10-8 inch air brake 
pumps . . . • 


1700 
1000 


255 
1530 


41 
73 


. 85 
50 


170 
100 


551 
1753 







From which it will be 'seen that the 8-inch air brake pumps will cost more 
than three times as much as the air compressor to operate, and that the com- 
pressor will pay for itself in less than a year and a half. 



986 USE. 

When it is further considered that the compressor requires, if anything, 
less attention than a number of pumps, that the consumption of oil would cer- 
tainly be less for the compressor, and that the cost of repairs would be consider- 
ably in its favor it would seem that a railroad which continues the use of air 
brake pumps for shop purposes is maintaining a losing investment. — Railroad Car 
Journal. 



LOW-PRESSURE PNEUMATIC INTERLOCKING AT JERSEY CITY. 

As heretofore noticed in the Railroad Gazette, the Erie Railroad has lately 
installed at Grove street, Jersey City, about half a mile from the terminal passen- 
ger station, an interlocking plant made by the Standard Railroa'd Signal Co., of 
Troy, N. Y., in which all of the switches and signals are worked and controlled 
by compressed air. The system is that of the Pneumatic Railroad Signal Co., oi 
Rochester, whose plant on the New York Central, at Buffalo, N. Y., was described 
in the Railroad Gazette of July 8, 1898. The Standard Company is now the sole 
licensee for this country under the patents of the Pneumatic Company. 

The accompanying illustrations show some of the details of the switches 
and signals at the Jersey City plant; there are large numbers of freight and 
switching movements. 

The interlocking machine has 59 working levers and five spare spaces. The 
design of this machine has been considerably modified since the publication of our 
former description. A view of one of the machines — not that at Grove street, but 
one substantially similar in appearance — is shown in Fig. 422. The principal fea- 
tures of the system are the same as those which were shown in connection with 
the Buffalo machine. No electrical apparatus is used ; the working air pressure is 
IS lbs. per square inch ; the pressure in the operating and indicating pipes is 7 lbs. 
per square inch, and these latter pipes are normally under atmospheric pressure 
only — that is to say, at all times except when a movement is to be made or an 
indication is to be given. The final portion of the stroke of the lever is automatic, 
so that as soon as the signalman has pulled a lever to initiate a switch movement 
or a signal movement, he can at once turn his attention to the next lever which he 
has to pull, without waiting for the return air-impulse. 

The arrangement of valves and pipes forming the connection between the 
interlocking machine and a switch cylinder is shown in Fig. 423. The principal 
parts are: S, switch rails; si, lock bar; s, switch rod; M, motion plate; C, switch 
cylinder ; D, indicating valve ; R2, R3, R4, R5, controlling valves ; L, L2, operating 
bar and slide valves; I, I2, indicator cylinders; H, interlocking tappet; X, air 
reservoir. 

To change the position of the switch the signalman grasps L by the handle 
and pulls it out. In doing this he admits air (from the main supply through the 
valve L2) through pipe a to valve R5, which opens communication from the sup- 
ply pipe X to the right-hand end of cylinder C, pushing the piston to the left. 
Observing now the slots L and M, it will be noted th^t after about one-half of the 
stroke of L has been completed it is stopped by the piston rod of I2 ; but the 
operation of valve Rs, already accomplished, causes M to move through the whole 



USE. 



987 



of its stroke. This stroke of M is uninterrupted, but we may consider it in three 
parts. The first part, say one-third, does not move the switch, but valve D is 
moved far enough to close the two pipes on its right, while those on its left 







■■■■■■■■■■ii i 


«(»?. 

-^,i 


■■HMM|gt> 




l| 





are open to the atmosphere. At the same time lock bar si has been liberated at S2. 
As M moves through the next or middle portion of its stroke, it moves the 
switch; but it now produces no effect on valve D, because the rod of D is now 
engaged by the straight portion of its slot in plate M. The switch being set, the 



988 USE. 

third and final part of the stroke of M locks the switch by pushing sio through a 
hole in si ; and also (but not until after sio has entered its hole) the plate changes 
valve D so as to connect together the tvvro pipes at its lower end. This conveys 
pressure from the supply through R5 and D to valve R3, which valve admits 
air from the supply to I2, forcing the piston rod upwaid, and, by means of the 
diagonal portion of the slot in bar L, forcing this bar to complete its stroke. This 
return action takes place at ordinary distances in from one to three seconds. 

By the action of L2 pipe a is now opened to the atmosphere. Valve R5 is 
now released from pressure, and R4 is closed; so that the right-hand pipe to 




W^ 






U 



•^R^ 

^^--1 



'ka 



iTy .T> ^ I 

jT» • 






FIG. 423 — SWITCH MOVEMENT. 



Cylinder C and its connection to and through D are open to the atmosphere. 
All four operating pipes are now at atmospheric pressure. 

By the movement of L, tappet H has been moved so as to produce the 
proper mechanical locking of conflicting levers (in the first part of the stroke of 
L) and the proper unlocking (in the last part of this stroke), in the same manner 
and sequence that the same interlocking would be effected in a mechanical inter- 
locking machine. 

To move the switch back to its original position, the opposite set of pipes is 
used. The bar L is pushed to the right ; air through b actuates R4, and the return 
indication to the cabin actuates R2 and lifts the piston in I. 

To work a signal, valves and operating pipes are used of the same general 
style as those for a switch, but there is only one indicating valve and one indicat- 
ing cylinder, as it is unnecessary to assure the attendant that a signal is in the go- 



USE. 



989 



ahead position. The signal connections are shown in Fig. 424. The principal parts 
are: A, signal arm; A2, signal cylinder; A3, lever to work indicating valve; B, 
indicating valve ; R2 and R3, diaphragm valves, controlling the admission of air 
to the top and bottom, respectively, of the signal cylinder; Ri, diaphragm valve 
controlling admission of air to cylinder I. The signal being in the normal or 
danger position, the indicating valve B is in a position to maintain a connection 
between the two pipes attached to it ; but the instant the signal arm leaves the 
horizontal position the valve shuts off this connection. 

To change the signal the signalman pulls L to the left, the whole length of 
its stroke. By this movement L2, admitting air to pipe a, actuates valve R3, 
which supplies air to the lower end of cylinder A2 and pushes up the piston, put- 




FIG. 424 — SIGNAL MOVEMENT. 



ting the signal in the inclined or all-clear position. The air impulse is transmitted 
so quickly that at the average distance — say 500 ft. and less — the movement of the 
signal is practically simultaneous with the movement of the lever. The signal 
remains in the inclined position as long as L is pulled to the left. To restore it to 
the normal or stop position, L is pushed to the right until it is stopped by the 
piston rod of I (at the end of the horizontal part of the slot in L). With L in 
this position, pipe b is charged and valve R2 is opened. The passage between 
pipes e and n (through B) is now closed, so that the opening of R2 admits air 
from the supply to the upper end of A2. This restores the signal to the horizontal 
position, and by means of A3 opens valve B. Air now passes from e through b 
and n to Ri, and the latter causes air to enter I and complete the return stroke of 
L by the action of the piston rod on the diagonal part of the slot. Pipes b, e and n 



990 



USE. 



are now at atmospheric pressure, and th.e parts are in the same position as at the 
beginning. 

In Fig. 425 is shown the diaphragm valve, which is called the "relay," its 
function being similar to that of an electromagnetic relay in electrical apparatus. 
This valve is actuated by air at 7 lbs. pressure. This pressure, admitted beneath 
the circular rubber diaphragm 8 in. in diameter, pushes up the cylindrical valve, 
placed vertically in the upper part of the case, and thereby liberates air at 15 lbs. 
per square inch to move the piston in the switch or signal cylinder. The move- 
ment of the diaphragm is only H in. 

The low-pressure pneumatic interlocking machine is made up of three 
principal elements: (i) A row of slide valves (called "levers"), like that shown 
in outline at L and L2, Figs. 423 and 424. The only physical labor imposed on the 
signalman is that involved in pulling out and pushing in these valves. (2) A 
mechanical interlocking frame placed vertically on the front of the machine. This 
is of the common mechanical type, like the Saxby & Farmer or the Johnson, but 




FIG. 425 — DIAPHRAGM VALVE. 



with the parts made about half the usual size. The manner of connecting the 
"lever" with the interlocking is indicated by the position and arrangement of the 
tappet H in Fig. 423. (3) The indicating cylinders and their relays on each 
"lever" as shown in Figs. 423 and 424. 

The operating and indicating pipes extending to the switches and signals 
are ^ in. in diameter. The supply pipes from the air reservoirs are larger, the size 
being varied according to the number of switches and signals to be supplied. 

The air is first run through a cooling frame for the purpose of precipitating 
moisture; but with low pressure the company finds that there is practically no 
trouble from moisture in the pipes. 

Both the manufacturers and the railroad company give favorable reports of 
their continued experience with the plant at Buffalo. The cost for repair material 
at that plant has been less than $4, and it is believed that the wearing parts of the 
machine have been so well designed that the maximum of durability can be 
expected. These parts have very light service and they are made interchangeable, 
so that they can be quickly and cheaply renewed. 



USE. 



991 



The automatic completion of the stroke of the lever by the return indication 
is found to be a decided convenience in a busy yard. Where a signalman, after 
making the first half of the stroke of a lever, has to wait for the return indication, 
ihe delay, though very short, is yet an appreciable addition to his cares, for he 



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delays going to another lever until he has finished his duty with the first one. 
But with the automatic movement he at once turns his attention to the next lever 
and thus stands ready (waiting perhaps a second or two) to move tl^t as soon as 
it shall be freed by the interlocking. Any failure of the automatic movement 



992 



USE. 



would, of course, prevent a liberation of the second lever, as the locking bar or 
bars holding it would not release it unless the preceding lever completed its stroke. 
The Standard Railroad Signal Co. has now under construction six low- 
pressure plants, as follows : For the New York Central & Hudson River R. R. 
Co., a 96-lever machine at Suspension Bridge, N. Y., a 48-lever machine at Hoff- 
man, N. Y., and a 176-lever machine at the Grand Central Station, New York 
City; for the Chicago & Western Indiana at Chicago, a 40-lever and a 48-lever 
machine; and at the Grand Central Depot, Chicago, an 8o-lever machine for the 
Chicago Transfer & Terminal Railroad. — Railroad Gazette. 



ELECTRICITY AND COMPRESSED AIR. 

Electricity and compressed air are in many things friends, not competitors. 
One should be the hand-maiden of the other to give mutual aid and encourage- 
ment. In some things electricity is supreme, and though compressed air were "as 
free as air" it could not compete. Friendly rivalry of this kind is the very essence 
of development and prosperity. 

Manufacturers of air compressing devices and all friends of compressed air 
will agree that the stimulus given them by recent developments in electricity is at 
the bottom of present prosperity in air compressing and air using devices. Com- 
petition has not only been the life of trade in this line, but engineers and inventors 
have watched and profited by the new uses of electricity, creating as it has new 
fields, in some of which air power serves a useful purpose. An instance of this 
co-operation is seen in most of the large railway yards in America. 

The Electro-Pneumatic switch and signal system is a combination of com- 
pressed air and electricity, each performing its part, and each recognized as the 
best power for the purpose. This system is considered the most comprehensive 
now in use. It is in constant operation at the Pennsylvania R. R. terminals in 
Jersey City, Philadelphia and Pittsburg; the Philadelphia & Reading terminal, 
Philadelphia ; the Union Station at St. Louis ; the Chicago and North Western R. 
R. terminal, Chicago; at the Boston & Maine terminal, Boston, and the Com- 
munipaw yards of the Central R. R. of N. J. The compressed air may be con- 
veyed along the road bed 20 miles in each direction from the compressor station. 
Electricity runs parallel with it and serves to open or close valves which admit 
compressed air to pistons which are connected with the switches and signals. 

Electricity handles the trigger while compressed air is the power which does 
the work. 

Here is where air power comes in to the best advantage. It may be trans- 
mitted a long distance with little or no loss provided the pipes are tight and the 
velocity of flow is not excessive. It does not lose power through changes in tem- 
perature. 

When released or led from the main into a cylinder it acts instantly with a 
force that is limited only by the area of the piston and the air pressure. After 
doing its work it is readily exhausted. All this is accomplished by very simple 
apparatus that is easily understood and readily repaired in any machine shop. 



USE. 



993 



We mention this as one and perhaps the most important case where elec- 
tricity and compressfed air are combined in useful service. 



COMPRESSED AIR REFRIGERATION- 
MACHINE. 



-THE EARLIEST ICE 



The earliest known appliance for making ice by compressed air seems to 
have been invented and put into actual practice by Dr. John Gorrie, of New 
Orleans, La., whose patent dates May 6, 185 1, although ice was actually made 
in his machine at Apalachicola, Fla., in the summer of 1850. 

The machine consisted in its essential operating parts of an air compress- 
ing cylinder and piston operated from a crank-shaft by connecting rods. 

A small injection pump operated from a cam on the main shaft, so ad- 
justed as to inject a small spray of cold water into the cylinder during the latter 




FIG. 426 — FRONT ELEVATION — THE EARLIEST ICE MACHINE. 



part of compression at each stroke of the piston ; thus being the leading practical 
application of the injection system for cooling the air during compression; the 
compressed air and injected water being driven together through the exit valves 
and through a coil of pipe immersed in a tub of cold water, to the receiver, from 
which the injected and condensed water was drawn off through a waste cock at 
the bottom. 

On the same platform and connected with a crank on the main shaft, was 
located the expansion cylinder with its piston and connecting rods. 



994 



USE. 



E. Expansion cylinder injection pump, drawing brine from the jacket W 
and forcing it in a spray into the expansion cylinder, by which the brine is 




FIG. 427 — END VIEW — THE EARLIEST ICE MACHINE. 

quickly cooled and discharged with the cold air into the upper section of the 
brine jacket and tank. 

J. The freezing can or tank. 

A charging tank containing fresh water for supplying the freezing can, is 
placed overhead. 

The other lettering indicates details readily understood by inspection. 



ARTIFICIAL ICE. 

On page 993 of this book, a description, with illustrations of the first 
machine used for the production of artificial ice. This machine was invented by 
Dr. John Gorrie, of Apalachicola, Fla., and its interest and importance are based 
upon the fact that the fundamental principles involved by which low temperatures 
were reached are practically identical with present theory and practice. Dr. 
Gorrie used compressed air to produce cold, and though the important industry 
of refrigeration is now mainly based upon the use of ammonia, yet the principles 
involved are the same. Dr. Gorrie, in his specifications, said : 

"It is a well-known law of nature that the condensation of air by com- 
pression is accomplished by the development of heat, while the absorption of 



USE. 995 

heat from surrounding bodies, or the manifestation of the sensible effect com- 
monly called cold, uniformly attends the expansion of air, and this is particularly 
marked when it is liberated from compression. The nature of my invention 
consists in taking advantage of this law to convert water into ice artificially by 
absorbing its heat of liquefaction with expanding air." 

We neglected to mention the fact that the illustrations and interesting 
description given of this apparatus were furnished by Mr. George H. White- 
side, of Apalachicola, Fla., who erected the Apalachicola ice factory, and who 
is now the general manager of the Apalachicola Ice Co. 

The substance of Mr. Whiteside's paper was given in a more extended 
article by him, which was published in "Ice and Refrigeration," in May, 1897. 



REFRIGERATION BY COMPRESSED AIR. 



DESCRIPTION OF A SYSTEM WHICH HAS BEEN IN EXTENSIVE USE FOR YEARS IN THE 

UNITED STATES NAVY. 

In the "American Machinist" for December 30, 1897, Mr. Richard E. Chandler 
describes his failure to cool water by blowing through it previously compressed 
and cooled air. Some editorial remarks upon this failure in the same issue 
express a desire that others will be encouraged to recount their experience in 
this line, and having had a large and varied experience in the use of compressed 
air for cooling refrigerating compartments in buildings and on ship board, in 
cooling potable water and also in cooling strong brine for use in ice-freezing 
tanks, I feel that I ought to accept the challenge. 

Contrary to the experience of Mr. Chandler, my experience has been a 
successful one; a process and apparatus for dynamic refrigeration, employing 
compressed air and effecting all the results above named, invented and put into 
use by me, has been in extensive use for years in the United States Navy, has 
been adopted for the Japanese war vessels, and is also in operation on many mer- 
chant and passenger steamers and steam yachts. 

I would very much like to make the mode of cooling by compressed air 
comprehensible to the ordinary steam engineer. Though this is by no means an 
easy task, with permission of the editor I will attempt it. 

All dynamic or mechanical refrigeration by use of compressed air or other 
gases depends upon the following fundamental principles, which have been both 
mathematically and experimentally demonstrated: 

(a) The performance of work by the molecules of any substance or ma- 
terial, as by air or steam in expanding, is done at the expense of heat in such 
substance or material ; heat is thus converted into work. 

(b) The performance of work upon the molecules of any substance or 
material, as in compressing air or steam, results in an increase of heat in the 
material ; work is thus converted into heat. 

(c) If air, or other gas, be first compressed, and the heat produced by the 
work of compression be then taken out of it (cooling by water is the usual way 



996 USE. 

of doing this), and if it then be expanded, expending the work of expansion upon 
some other exterior body or substance, it gets very cold, and in this state 
may be used to extract heat from, or cool, other substances or bodies. 

The italicized words express a condition absolutely essential to a success- 
ful refrigerating process. 

It was reasoned in the editorial remarks upon Mr. Chandler's failure (above re- 
ferred to) that as air cannot expand without performing work, and that as the 
performance of work always implies a simultaneous or prior conversion into 
mechanical energy (actual or potential) of the heat equivalent of the work, and 
as the conversion of the heat equivalent into actual mechanical energy in the 
performance of work by expanding air is coincident with the expansion, com- 
pressed air, following full stroke in an air engine (thus doing no work, but acting 
the same as a liquid or solid to simply transmit pressure), ought, when expand- 
ing from the exhaust, to produce the same iinal cooling effect as when expanded 
in any other way. 

Now, it is true, as stated in this argument, that air cannot expand at all 
without doing work ; that the expansion of a definite weight of air from a given 
pressure and temperature to a given lower pressure and temperature without any 
accession of heat while expanding always results in the performance of a definite 
quantity of work, and that this work is the equivalent of a definite amount of heal 
previously contained in the air which expands, and which cannot simultaneously 
exist as both heat and work; but it does not, therefore, logically follow that 
when the last part of a cycle of operations in compressing and expanding air has 
been reached, there will have resulted a reduction of temperature (below the 
initial temperature of the air passed through the cycle) representing anything 
more than a small fraction of the heat equivalent of the work performed by the 
expansion. 

Whether the iinal reduction of temperature below the initial temperature 
will be th equivalent of the work of expansion (less what may be lost through 
frictional reheating) or not, will depend upon the application of that work. 

If, subsequently to the expansion, all the work generated t)y it be recon- 
verted into heat, before the close of the cycle of operations, and this heat be 
expended in reheating the expanded air, there will be no final lowering of tern- 
perature ; there will generally be some final increase of heat due to friction. 

Therefore, in the argument (issue of December 30) under consideration, 
though the premises are all sound, the conclusion is not justified thereby. The 
compressed air after following the piston full stroke is capable of yielding the 
full cooling equivalent* of the work of expansion, if expanded under proper con- 
ditions; letting it exhaust freely into the outer air, or into water, as Mr. 
Chandler did, is not the right way. 

Pushing the compressed air after it has followed full stroke (and before 
expanding) into the cylinder of another engine of such size and cut-off that 
at the end of its stroke the expansion would be complete— the piston applying the 



* Cooling IS the passage of heat out from a body or neqatire beating as distinguiehed from 
VO%itwe heatin? or the passage of heat into a body. The equivalent of either is numerically expressed 
in thermal units, the number expressing passage of heat out having ihe minus sign, while that 
expressine passage of heat in has the plus sign. In this mathematical sense it is therefore as logical 
to write cooling equivalent " for loss of beat by performance of work as " heat equivalent " for gain 
of heat in a body upon which work is performed. 



USE. 997 

work of expansion to some exterior object — would be, though indirect, a right 
way to get the full available cooling effect. But how is it that expansion into a 
surrounding medium fails to do the same thing? 

To gain clear ideas we must regard the whole cycle of operations — not 
merely some part of it — and determine whether the cooling effect of one opera- 
tion is, or is not, counteracted by another. 

Cycle of Three Operations. — Compression not followed by cooling before 
free expansion from a valve opening adds the full heat equivalent of the work 
of compression to the finally expanded air; the latter will then be hotter and 
will have a larger volume immediately after expansion than before it was com- 
pressed, and the third operation of the cycle is its giving off of this heat, result- 
ing in its contraction and the resumption of its normal volume. This cycle is, 
therefore, a heating cycle in its final stage, notwithstanding there is a full expan- 
sion of the compressed air. The cooling due to expansion in one operation is 
not only neutralized in another part, but the entire heat equivalent of the work of 
compression is ultimately transmitted to the medium into which the air is finally 
discharged. 

Cycle of Four Operations. — This may be the same as the above, except that 
the air is cooled in some way (say, by water) after compression, and then al- 
lowed to expand freely out into a surrounding medium. The heat equivalent of 
the work of compression is carried away in the cooling water. Now, if the ex- 
pansion be made freely into a gaseous or liquid medium the air expanded will at 
first be cooled by the full equivalent of the work of expansion, but only a small 
fraction of this cooling effect will remain available at the end of the expansion. 

This can be made plainer by an example of such treatment of a specific 
quantity of air ; the surest way to get right on any question of thermodynamics 
is to deal with specific quantities. 

JLet us deal with one pound of air, supposed to be already compressed to 
220.5 pounds per square inch (15 times atmospheric pressure at sea level) and 
cooled to 72 degrees Fahr. (or 531 degrees absolute temperature) ; thus two of the 
operations of the cycle have already been performed. 

Let us suppose this air confined in a metallic cylinder of 12.555 inches inter- 
nal diameter and the same internal length. Such a cylinder will just contain the 
one pound of air, which, at the stated temperature and pressure, will have a 
volume of 1540.68 cubic inches. 

Let us suppose that one end of this cylinder is so arranged that it can 
be fully and suddenly opened or closed, thus permitting the freest conceivable 
expansion and instantaneous closure. 

Let this cylinder, charged as assumed, be placed in an otherwise vacuoua 
inclosure hermetically closed and having a net cubic capacity of I1.415 feet 
over and above the space occupied by the charged cylinder, and let it be also 
supposed that the walls of this inclosure have the temperature of 72 degrees Fahr., 
and that they are so well insulated that no heat can penetrate them. 

Now, suppose the removable end of the inclosed and charged cylinder to be 
suddenly opened, and instantly closed again the moment that the air has ex- 
panded to atmospheric pressure in the previously vacuous space. Three of the 
operations of the cycle have now been performed; the previously vacuous space 
outside surrounding the charged cylinder will be filled with air at 72 degrees 



998 USE. 

Fahr. and at atmospheric pressure; the incloure cylinder will be filled with very 
cold air at atmospheric pressure, which is available for refrigerating efifect in 
the fourth operation of the cycle wherein the restoration of the air to the same 
pressure and temperature as before the compression is completed. The amount of 
this cooling effect is easily calculable, on the supposition that it can all be prac- 
tically applied. The theoretical temperature of the air remaining in the cylinder 
is 217.08 degrees Fahr.; this is a very low temperature, but, as the air in the 
cylinder is only 0.163 pound, the total amount of refrigeration is small as com- 
pared with what -is possible under proper conditions. The total theoretical cool- 
ing effect possible from one pound of air expanded from 220.5 pounds per square 
inch and 72 degrees Fahr. down to atmospheric pressure, if applied to cooling 
water from 80 degrees Fahr. down to 40 degrees Fahr. is 61.2 negative British 
thermal units, of which there are obtained in our supposed experiment not quite 
10 B. T. U. 

The total work of expansion is 52.992 foot pounds, which is all expended 
in generating velocity in the one pound of air at the time of its release from 
pressure. It would be easy to calculate the average velocity thus generated, but it 
is sufficient to note that what air remains in the cylinder has substantially no 
velocity. The 0.877 pound of air shot out strikes the walls of the inclosure and 
the impact and arrest of motion regenerates the heat which previously generated 
the work, and thus all the final cooling effect is confined to the air remaining in 
the discharged cylinder. 

The interval of time between the discharge and the impact which reheats 
the air is so short that, practically, these events may be regarded as simultaneous, 
and the air forced out of the cylinder might be considered practically as per- 
forming work and expending it upon itself simultaneously, so that the 
cooling effect of the expansion is neutralized by the heating effect of the work 
performed upon itself; but, as a matter of fact, the events are successive; heat is 
converted into work, work is converted into the potential of velocity and, 
lastly, the potential of velocity is converted into heat again at the instant of 
impact. 

If, instead of into small vacuous space, the compressed air were allowed 
to escape into a limitless vacuous space, it would never lose its velocity and never 
regain its temperature, and consequently the cycle of operations would never be 
completed.* 

If, instead of into the vacuous space, the air were permitted to expand 
freely into a gaseous or liquid medium, the reheating effect of the arrest of its 
motion by impact would be just the same, and all the residual cooling effect would 
be that of the air remaining in the cylinder. 

The heating of gaseous molecules by impact against surfaces of solids 
or liquids, or against other gaseous molecules, is precisely analogous to the heat- 
ing of projectiles when shot against targets or when they meet in their 
trajectories. 

The supposititious experiment described explains why in an air engine fol 
lowing full stroke the air remaining in the cylinder until it is pushed out 
gets very cold. W hile the air is expanding out of the exhaust what so escapes 

^.^^- ^ cf^P'ete cycle of operations restores the air to the same volume and temperature it had 
previous to compression. 



USE. 999 

reheats by impact and a little by friction in passing through the nozzle ; while that 
which, after more or less complete expansion, is thrust out by the returning 
piston is very cold, because it has expended its work of expansion in shooting 
out the air in advance of it, and, when at last thrust out, it has practically no 
velocity, and cannot, therefore, be reheated by impact. There is, therefore, in 
the operation of such an engine, the local, restricted cooling effect which causes 
annoyance by freezing up ports, precisely as stated in the editorial remarks upon 
Mr. Chandler's failure. 

Let us now suppose the cylinder containing the compressed air to be re- 
placed by a cylinder of the same internal diameter. With a piston having a 
stroke of 85.7 inches, the cylinder being so insulated that no heat can pass into 
or through its walls from or to the contained air (expansion or compression 
of gases under such conditions is said to be adiabatic). 

Our one pound of air, compressed and cooled as before, will now occupy 
12.555 inches of the length of the cylinder behind the piston. Therefore, when 
the air has followed the piston through this distance, let there be a sharp cut-off 
and thereafter let the air expand, driving the piston, whose rod (extending out to 
some means for performing work, say, a cross-head, pitman and crank) applies 
all the work of expansion to the performance of outer work, such as pumping 
water, assisting to drive an air compressor or lifting a weight. At the end of the 
stroke the whole space in the cylinder except that occupied by the piston will be 
filled with air at a pressure of 14.7 pounds per square inch, and at the theoretical 
temperature of 217.08 degrees Fahr. Now when the exhaust opens this air will 
not rush out, of itself; there will be no further expansion, and the air will re- 
main in the cylinder till pushed out; when so pushed out it has a comparatively 
low velocity, and, therefore, is heated very little by friction and scarcely at all 
by impact ; we, therefore, reach the final stage of the cycle of operations with the 
whole pound of air very cold and theoretically requiring 61.2 thermal units to re- 
store it to its condition before compression, and thus to complete the cycle. All 
this heat will now be abstracted by the cold air from warmer surroundings or 
contiguous substances, whether water, air, substances to be preserved by refrig- 
eration, or brine for use in an ice-freezing tank. 

In practice, of course, such a proportion of stroke to diameter in an air- 
expanding cylinder would never be met with; it was only assumed for the pur- 
pose of argument. Practically, also, theoretical results are not very nearly 
attained, as perfect adiabatic compression or expansion is impracticable, and there 
are frictional and other losses. 

The more gently the air can be pushed out of the cylinder the less reheat- 
ing it will receive. Suddenness of exhaust is detrimental. 
The whole matter can be summed up as follows : 

(a) Air in expanding always performs work. 

(b) As we cannot expand into a limitless vacuum, as much of this work 
as is converted into velocity, will be reconverted into heat by impact. 

(c) Because, if the air be expanded out of a valve opening, without fol- 
lowing and expanding behind a piston, all the work of its expansion is con- 
verted first into velocity and immediately thereafter by impact converted into heat, 



looo USE. 

the cooling effect of the expansion is immediately neutralized by this heat, and 
this method of cooling produces only a small local refrigerating effect plus that 
resulting from the slight molecular cohesion. — Leicester Allen, in American 
Machinist. 



ALLEN REFRIGERATING PROCESS. 

In these days when people are looking toward liquid air as a means of 
refrigeration it must not be forgotten that compressed air already plays an im- 
portant part in refrigeration and particularly in. marine service. 

What is called the Allen Dense Air Machine is installed on many boats of 
various description. The process is about as follows : 

Air under pressure (generally sixty pounds) is taken in by an air com- 
pressor and compressed to commonly 210 pounds. This heats up the air, storing 
in it such amount of heat as is the equivalent for the labor expended upon the 
compression. It is then passed through a copper pipe coil immersed in circulating 
water and this removes the heat to nearly the temperature of the water. 

Then the air passes into the valve chest of the expander, which is, in con- 
struction, a usual steam engine with a cut-off valve. The valves admit the highly 
compressed air upon the piston to a certain point of the stroke and then shut it off. 
The piston continues to travel to the end of the stroke, the air exerting pressure 
upon it (constantly diminishing, of course). This takes out the air in such a 
quantity of heat as the labor performed by the air, while expending, requires for 
its performance. 

The result is a very low temperature of the air at the end of the stroke. 
The return stroke of the piston pushes it out through thickly insulated pipes to 
such places as are to be refrigerated, viz. : the ice making box, the meat chamber 
and the drinking water butt. In all these the air is, of course, tightly inclosed in 
pipes or other strong apparatus, being under the original pressure at which it 
entered the compressor (sixty pounds) and the cold is given out through the 
metallic surfaces. 

Frozen meat can be kept practically without change for an almost indefinite 
time. When kept at nearly the freezing point without change it may be kept for 
a number of weeks in good condition. A good practical rule for the amount of re- 
frigerating pipes required in the meat chamber to keep this at the freezing point 
is : One square foot of pipe surface for every two and one-quarter to two and 
three-quarters square feet of interior surface of well insulated meat chamber, 
omitting interior divisions. It is necessary to arrange the piping so that the air 
in them is compelled to pass all surfaces with fair velocity. 

From the meat chamber the cold air goes to the refrigerating pipes in the 
drinking water butt, passing first to the bottom layer and then gradually upward. 

After that it returns to the compressor inlet of the machine. 

In arrangements where not all the cold is taken out of the air by the refrig- 
erator apparatus, the highly compressed air after cooling in the copper coil is 
further cooled in a special apparatus, where it is brought into surface contact with 
the returning and still cold air, before entering the expander. 

Temperatures of 70 degrees to 90 degrees below zero are thus practically 
obtained in usual machines. 



USE. looi 

COLD STORAGE AND COLD ROOMS FROM COMPRESSED AIR. 

In view of the largely increasing demand for the means of preserving food 
in the warmer sections of 'the United States, and in tropical climates, where ice 
cannot be obtained, or the cost is so great as to preclude its use, the use of com- 
pressed air as a constant cooling medium is one of the means at the command 
and control of every one who is able to place a small outlay for a valuable boon 
to household comfort; and for the profit that may be realized from the power 
to preserve fruit, vegetables and meat for sale, or for the time and opportunity for 
shipment to a market. 

There are large tracts of country in the Southern section of the United 
States in which are situated plantations and farms, the owners and managers 
ol which, having the financial means to supply comforts to life by the use of cold 
preserved food, who are entirely beyond the reach of ice, either natural or arti- 
ficial, and to whom such wants may be supplied by the means of any small power 
such as a windmill, a waterfall or a gasoline engine, operating a pump for the 
compression of air. In Mexico, the Central American and South American 
states, the field for useful work by wind and water power alone for contributing 
to domestic comfort by the preservation of food is immense; where power from 
nature as through a windmill or waterwheel can be utilized. The distance need 
not be considered beyond the cost of a small pipe for conveying the compressed 
air, as a considerable length is needed to cool the air to its normal temperature 
which has been heated by the operation of compression ; when by expansion to at- 
mospheric pressure the same amount of heat may be eliminated from the expand- 
ing air as was accumulated by its compression, and from which a large cooling 
efficiency may be obtained. 

The graphic diagram has been made to show at sight the cooling effect pro- 
duced by the free expansion of dry air from various pressures and from the 
normal temperature of 60 degrees Fahrenheit. The conditions of air expansion 
foi any natural temperature of the stored air may be found by simply adding the 
difference to the expansion column when normally above 60 degrees, or subtract- 
ing when below 60 degrees. Thus, in an atmospheric temperature of 80 degrees, 
the cold produced by expanding from 20 pounds pressure would be minus 67 
degrees instead of minus 87, as shown in the diagram. From 50 pounds pressure 
and 90 deg. atmospheric temperature, the cold air of expansion would be minus 
108 deg. instead of minus 138, as in the diagram; thus for any atmospheric condi- 
tion of temperature and pressure, the theoretical condition of cold by expansion 
may be known by simple inspection of their several relations as shown in the 
diagram. 

The diagram shows much that is interesting in regard to the general con- 
ditions and effect of air compression and expansion. It will be seen that the 
column of pressures on the right corresponds with the column of heat developed 
by compression on the left, while the upper or adiabatic curve shows the condi- 
tion of temperature, pressure and volume at the moment of compression. The 
lower or isothermal line shows the shrinkage of the volume due to the cooling 
of air to its normal temperature. 



I002 



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FIG. 428. 



USK 1003 



^B The vertical dotted lines from the intersection of the isothermal line with 
the horizontal lines of pressure, meeting the atmospheric line, from the starting 
points for the curves of expansion extended on the same scale of temperature cor- 
responding with the scale of compression. 

The intersection of the dotted lines extended through the curved lines of 
expansion show also in a graphic way the fractional expansions from one stage of 
compression to another lower one as measured by the expansion scale at the left 
hand side. Thus a volume of air at 60 pound pressure and 60° temperature, when 
expanded to 30 pound pressure, its temperature will fall to the intersection of the 
extended dotted line of 30° with the 60 pound curve, which measured on the 
expansion scale is — 57°, and so on for any other pressures. 

In applying the conditions of air expansion to the practical effects of refrig- 
eration or the cooling of rooms for cold storage and preservation of food, a large 
departure from the theoretical figures for the degree of cold by air expansion 
must be made on the favorable side for success. 

The absorption of heat from the walls of a cold room, the cooling of a large 
body of air in the room and of food products stored and the greater loss from 
frequent opening of a cold room for the removal and refilling, with the natural 
leakage of cold air around the doors, makes the margin of loss in cold air pro- 
duction a larger one than at first appears when brought into actual use. 

The amount of specific heat contained in a given volume of air is about 
1-800 of the amount contained in the same volume of water for any number of 
degrees change of temperature at ordinary climatic temperatures, so that there is 
a large margin between the volume of cold air required to cool a room filled with 
air only and the volume required to cool a room filled with fruit, vegetables, milk, 
butter or meat containing from 50 to 90 per cent, of water and of which the solid 
parts also have a far higher specific heat than air. 

This property of water-loaded food accounts for the time required to cool a 
loaded cold storage room over the time required for cooling an empty one, as well 
as the necessity for so packing the material of storage that the cold air can circu- 
late freely and bring every part to the required temperature in the shortest 
possible time. 

As to the work that compressed air will do in cooling rooms, there is a large 
marginal range in the quantity of free air required for a specific temperature, due 
to the conditions of temperature of the material to be cooled and the amount of 
compression in the air to be expanded for this duty. 

Assuming, for example, a cold room for a farm or plantation of 1,000 cu. 
ft. capacity, or say 12 ft. square by 7 ft. high, thoroughly insulated, with a doubJe 
door at side for storing ; a single or trap door with a small ventilator at top, with 
steps from the trap door for every-day use, and also lighted from the top. By this 
means a loss of cold air is prevented by its greater specific gravity holding it at 
the bottom. The room may be kept uniformly at 34° Fahr., in an outside tempera- 
ture averaging 80°. To cool such a room from 80° to 34° requires a loss of 
46° in a volume of 1,000 cu. ft. of air, say 'j'j pounds, the specific heat of which is 
0-22,77 water = i. Then 77 x 0*2377 = 18-3 heat units must be absorbed for 
every degree of change in temperature. Then 18-3 x 46° = 841 heat units must be 



I004 USE. 

cibstracted to bring it to 34° Fahr., leaving out the cooling of the walls, which 
will be only a matter of time in the initial operation. 

Assuming to use an air pressure of only 30 pound per sq. inch, then in the 
graphic diagram, tracing the dotted line from the isothermal curve junction of 30 
pound and following its curve of expansion, we have — 138 x 60° to the atmos- 
pheric line = 198° difference in temperature by expansion from 30 pound pressure, 
or 198 heat units per pound of air. Then 

841 

= 4 -24 lb. or 555^ cu. ft. of free air at 30 lb. pressure will be required to cool 

198 

the room to 34°. 

A compressor of 5 cu. ft. per minute capacity, using less than one horse 
power will furnish enough air to reduce the temperature of the room from 80° to 
34° in about 15 minutes, and should then easily furnish cold air for absorption 
of heat from the material of storage and to supply the waste made necessary by 
ventilation and radiation with a constant work of less than a half horse power. 
This power comes within the scope of a cheap class of water wheels, water motors, 
and the smaller sizes of gasoline engines and windmills. 

Where intermittent power must be used, as with windmills and power 
engines, a system of storage of compressed air may be used with perfect satisfac- 
tion as affording a constant flow of air into the cold room and also into a small 
refrigerator, which will be found a most useful adjunct for kitchen use and the 
cooling of drinking water. 

The amount of pipe surface required for cooling compressed air to the nor- 
mal temperature is a matter of much importance, as its delivery at the point of 
expansion, to be effective, must be at, or very near, the temperature of the outside 
atmosphere. 

The method of keeping the air-cooling pipe at the proper temperature fixes 
the amount of pipe surface to be provided. 

For 30 pound pressure, 15 sq. ft. of cooling surface per cu. ft. of free 
air used per minute is a fair proportion for an air-cooling coil exposed to a free 
circulation of the atmosphere and shaded from the sun's heat. 

This would indicate a coil of 150 feet of i>^-inch pipe for the requirement 
of a cold room as above stated, which may also include the leading pipe from, 
compressor to cold room, if favorably situated for cooling. Where it is convenient 
to use water for cooling, either by a sprinkler or by submerging the coil in a tank 
of water fed from a stream or by pumping, the size of the coil may be greatly 
reduced, according to the temperature of the water. 

For an intermittent power as a windmill, or a gasoline engine that would 
not be convenient to run at night, a storage of air will be necessary by the use of 
a proportionally increased power during the day for accumulating compressed air 
in tanks. 

The storage of sufficient air for a ten hours' run of the above plant will 
require tanks to hold about 1,200 cu. ft., or say three tanks of cylindrical form 5 
feet diameter, 21 feet long. As the atmospheric temperature always falls at night 
in tropical and semi-tropical regions, the conditions of compressed air supply may 



USE. 1005 

be much modified in the storage quantity above outlined, and where constant 
power can be obtained, the whole question of cold storage for private use becomes 
a cheap and simple one. 

The arrangement of the nozzle or orifice for delivering the compressed air, 
and at which point the expansion takes place, is important and requires its area to 
be exactly gauged to the proper size for the delivery of the desired volume of air 
at the assigned pressure. At 30 pounds pressure, air flows through an orifice in a 
thin plate at the rate of 525 feet per second. Then for the plant as above 
described, for the issuance of 5 cu. ft. of free air per minute under a compression 

5 

of 3 volumes in i is = 0.02777 cu. ft. of compressed air per second, and 

3x60 
o 02777 

= 0.0000529 of a square foot area. Then 0*0000529 x 144 = 0.0076176 

52s 
of a square inch. Then enlarging for the coefficient of efflux, the orifice should 
be }i inch diameter, with a valve back of it to shut off the air flow when required. 
Means should also be provided for blowing off any water that may condense in 
the air pipes or storage tanks by the cooling of the air after compression. 

With proper care and a moderate outlay the system of cold storage by com- 
pressed air becomes a simple, efficient and economical adjunct to the living com- 
forts of every home in a warm climate not blessed with a nearby ice-making plant. 

G. D. HISCOX, M. E. 



COLD STORAGE AND COLD ROOMS FROM COMPRESSED AIR. 

We have received a number of communications from our correspondents on 
the subject of a paper which we published, entitled, "Cold Storage and Cold 
Rooms from Compressed Air," by Mr. G. D. Hiscox. We publish some of these 
communications, and will be very glad to continue the discussion, which can not 
fail to be productive of good results. 

This is a subject about which a great deal may be said and concerning which 
there is a wide diversity of opinion. There are many things about compressed 
air in respect to which engineers differ ; in fact, we know of no science of equal 
importance which is less subject to well-defined rules than that of compressed air. 
The laws of thermodynamics are complex. Rules that apply to dry air must be 
corrected for air under normal conditions, for there is no such thing in general 
practice as dry air. Heat and cold, which are so much in evidence when treating 
of compressed air, are only relative terms. We do not really know what heat is ; 
in fact, our best judgment is that there is no such thing as heat; that it is only 
the sensible effect of motion ; hence, it is natural to expect that a paper upon 
"Cold Storage by Compressed Air" might contain matter so purely theoretical 
that engineers will not agree with the conclusions derived. 

Compressed Air does not pretend to be responsible for the ideas given by 
its correspondents over their signatures. Mr. Hiscox is a well known mechanical 
engineer of acknowledged ability and of wide experience ; he is as competent per- 



ioo6 USE. 

haps to treat of this subject as anybody else, and is just as liable to make mis- 
takes or to indulge in theories which may not accord with practice. The trouble 
is that we have so litle practice on this subject that our ideas and conclusions 
must be largely matters of theory. 

Prof. Sims, of the State University of Iowa, has very properly called at- 
tention to an error of figures in Mr. Hiscox's article. This has been corrected 
by Mr. Hiscox, who promptly saw the point made by Prof. Sims. 
I 

The error of as the relative heat value of equal volumes of air and 

800 

I 

water should have been and the result of the computation should have been 

3413 
divided by the specific heat of air .2377, making 17.9 lbs., or 232 cubic feet of air 
required to cool the room and extending the time of cooling to one hour. 

The actual expansion temperature from — 138 to the required temperature 
of the room is — 138 + 34 = 172*' Fahr., which should have entered the formula, 
841 

making it =3 40.88 lbs. of air, or 531.** cubic feet of air. The com- 

172 x .2377 

pressor of 5 cubic feet capacity would then require nearly two hours to reduce the 
temperature of the room to 34°, and somewhat longer when the room is charged 
with its storage of material having a greater specific heat than air. 

Mr. Dickerson makes the point that the figures given by Mr. Hiscox are 
entirely theoretical and that theoretical temperatures due to the expansion of cold 
air can not be approached in practice. This statement is, we think, quite true. 
The theoretical figures given by Mr. Hiscox, when based on the free expansion 
of air, can not be reached in practice ; but when the air is used to do work in the 
cylinder of an engine, as for instance a pump, the cooling effect is very great, 
and in degree we think it follows closely the theoretical figures. Where water is 
present — as it always is — the specific heat of water will affect the air and prever.t 
extreme temperatures being reached, but the simplest and most practical way to 
get a low temperature through the expansion of compressed air is by letting it do 
work and exhaust into the chamber to be cooled. The cold air is in this way 
produced exactly as the heat is produced at the compressor, and it should be equal 
in degree. The piston of an air compressor does a certain amount of work upon 
the air, this air does no work in return, hence the resultant effect of this work is 
heat. Heat and mechanical energy, or heat and work, are convertible terms. We 
can produce heat by work, or we can produce work through heat, converting; une 
into the other with as much certainty as we can convert ice into water, or elec- 
tricity into heat, or water into steam. 

Sir Humphry Davy, in the year 1799, published a paper giving the results of 
experiments which determined the true relation between heat and motion. He 
showed a case in which there was actual conversion of mechanical power into 
heat. This was accomplished by the rubbing together of two pieces of ice until 
they were melted and converted into water. In this case the heat which produced 



I 



USE. 1007 



this conversion could not have come from the ice, because after the melting had 
taken place the temperature oi the water was slightly above the freezing point, 
that of the ice remaining the same; nor could this have come from surrounding 
bodies because of the nature of the experiment, hence Davy reaches the con- 
clusion that "Heat or that power which prevents the actual contact of the cor- 
puscles of bodies, and which is the cause of our peculiar sensations of heat and 
cold, may be defined as a peculiar motion, probably a vibration of the corpuscles of 
bodies tending to separate them." 

In Davy's work on "Chemical Philosophy" he makes the statement that 
"The immediate cause of the phenomena of heat is motion, and the laws of its 
communication are precisely the same as the laws of the communication of mo- 
tion." 

The laws that govern the production of heat apply equally and in the same 
degree to the production of cold. We know that where pumps in mines are 
driven by compressed air, freezing at the exhaust is a common difficulty, and it is 
well known that the air discharged from the exhaust is cold. The degree of cold 
depends upon the expansion. If the air is admitted to the pump at a high pres- 
sure and is exhausted, the lowering of temperature will be greater than if 
admitted at a lower pressure. Where there is no cut-off, as in the case of a com- 
mon mine pump, it would seem that the low temperature is produced not so much 
within the cylinder as at the exhaust. With a cut-off valve as in the case of steam 
engines, the air is admitted, cut off, and expanded down to a point near atmos- 
pheric pressure before the exhaust takes place, in this case the lowering of tem- 
perature takes place within the cylinder; but with a common pump it is likely 
that the contraction of section produces at the point of contraction a very high 
resistance. 

This brings us to the consideration of an interesting and quite unex- 
plained condition of things. If we have a tank charged with compressed air and 
let the air be discharged through a free opening into a room, there will be prac- 
tically no reduction of temperature except immediately at the nozzle, and even 
here the reduction is slight. Mr. Moran, Mechanical Engineer for Sooysmith & 
Co., tried an experiment with air expansion with a view of freezing loose ground. 
He drove pipes into the ground which were connected at one end with a tank 
containing compressed air, and open at the other. These pipes were connected in 
series, so that when the valve was opened the air from the tank would pass 
through them, reaching atmospheric pressure at the other end. There was not 
only no reduction in temperature, but on the contrary there was a slight increase. 

This and similar experiments have shown us that the simple discharge of 
compressed air through an opening into the atmosphere does not produce refrig- 
eration ; but when this discharge takes place through a very fine opening, the cold 
is intense. Even liquid air has been produced by simply expanding compressed 
air from high pressures down to atmospheric pressure through contracted open- 
ings. We know that in electricity the passage of a current through a contracted 
medium, as for instance through a fine wire, produces heat. This is shown in 
the common incandescent lamp, yet when we pass compressed air through a finely 
restricted medium, as for instance an opening the size of a needle, the reverse is 



ioo8 USE. 

true — ^that is, cold is produced; and the higher the pressure of the air, or the 
greater the resistance, the more marked is the reduction of temperature. 

It has been suggested that in the case of air internal work is done in over- 
coming the resistance at the opening and that it is heat which is abstracted from 
the air in doing this work which accounts for the extreme low temperature results. 



Minneapolis, Minn., Dec. 31, '97. 
Editor Compressed Air:— 

Referring to the article written by Mr. G. D. Hiscox on "Cold Storage 
from- Compressed Air" (page looi). 

The refrigerating effect obtained by expanding compressed air through a 
small orifice is very small in proportion to the amoum of work expended in com- 
pressing it, on account of the frictional resistance of the contracted opening. The 
compressed air should be expanded against a piston doing work, then exhausted 
through a large opening at very near atmospheric pressure, to get the maximum 
cooling effect from it. I have tried the first way, and know how it acts. See also 
the effect on steam of throttling, for proof. 

MADISON COOPER, JR. 



Editor Compressed Air: — 

Dear Sir: — The article in the December number of Compressed Air, en- 
titled, "Cold Storage and Cold Rooms from Compressed Air," by G. D. Hiscox, 
is almost entirely theoretical in regard to the figures and data given, and admits 
of criticism for not impressing that fact more fully upon the mind of the reader. 
A person not familiar with the subject would be apt to arrive at erroneous conclu- 
sions after reading it; and if they were to put in a cold storage plant as figured 
and described, the writer is afraid that they would be sadly disappointed. 

The statement is made in the first part of the article that "when by expan- 
esion to atmospheric pressure the same amount of heat may be eliminated from 
the expanding air as was accumulated by its compression, and from which a large 
cooling efficiency may be obtained," and later in the article some computations 
for cooling down a room of 1,000 cu. ft. capacity are made, based on that assump- 
tion. The fact that the theoretical temperatures due to the expansion of cold air 
cannot be approached in practice seems to have been entirely ignored. 

The highest cooling efficiency with cold air is obtained by such machines as 
the Bcll-Coleman Cold Air Machine and the Allen Dense Air Machine. Even 
with these machines the pratical cooling effect is only a little over 40 per cent, of 
the theoretical cooling effect, and with an expansion orifice as described in 
article referred to, the cooling effect would be much lower, especially with the 
low pressure of 30 pounds per sq. in., as mentioned. In the cold air refrigerating 
machines referred to, the cooling effect is obtained by causing the air to do work 
in a regular engine. Theoretically the free expansion of air should produce no 
cooling effect, but actually there is some cooling effect, but not to the degree 
mentioned in Mr. Hiscox's article. If such a case is actually in practice where any 



r 



USE. 1009 



great cooling effect is obtained with as low a pressure as 30 pounds to the sq. in., 
the writer would like very much to hear of it. 

Very truly yours, w. h, dickerson, m. e. 

New York. 



Iowa City, Iowa, Jan. 3, '98. 
Editor Compressed Air: — 

Allow me the privilege of commenting on the article in the last issue on 
* Cold Storage and Cold P ~ ns from Compressed Air." 

The author states that the "amount of specific heat contained in a given 
volume of air is i-8ooth of the amount contained in the same volume of water" 
per degree range of temp. 

Specific heat is not an 'amount," and while it is clear to see that he means 
the amount of heat, or heat units, his fraction is in error. 

I lb. air = 13 cu. ft. == .2377 heat units per deg. range temp. 
13 cu. ft. H^O = 800 lbs. = 800 heat units per deg. range temp. 
I 

Ratio = about. 

3200 
Again having determined that 841 h. u. must be absorbed from a certain 
room to reduce it to 34° F., he first calculates that air at — 138° warmed to + 
34° (as min.) will give range of — 138 + 60 = 198°. 

But supposing this did not include error, he says : 
841 

"Then = 4.24 lbs. or 555^ cu. ft. of free air at 30 lbs. pressure will 

198 
be required to cool the room to 34°" — or say 25 per cent, of the amount required. 

A. v. SIMS. 



FREEZING OF GROUND BY EXPANSION OF AIR. 

A recent article in the November, '99, issue of this magazine, entitled 
"Allen Refrigerating Process," has called to mind a very unique application of 
the Allen Dense Air System of refrigeration. 

In excavating where quicksand is encountered work is greatly facilitated 
by freezing, and it was an instance of this kind that brought up the idea that com- 
pressed air could be adapted to the work; as the system of circulating brine is 
used in instances of this kind, but like most other appliances of this nature, it has 
its imperfections. Take for example a leaky pipe which by allowing the brine to 
come in contact with the frozen earth will soon destroy the freezing effect which 
has taken hours to accomplish. 

The instance in mind was in 1895, at the time of the building of the Speed- 
way along the Harlem River, wliere in excavating for the walls quicksand was 



lOIO 



USE. 



encountered. Sooysmith & Company, now known as the Engineering Contract 
Co., and who control the freezing process of excavation for this country, having 
met difficulties of this kind, decided to attempt the use of compressed air for 
freezing the ground prior to excavating. To accomplish this they equipped an air 
compressor with an air expansion cylinder mounted where the ordinary air com- 
pressor cylinder is placed and extended the piston rod through so as to connect 
by means of a coupling to the piston rod of the compression cylinder which was 
mounted on a foundation in line with the steam and expansion cylinders. The 
valves of the expansion cylinders were of the Meyer cut-off type and were 
operated by extending the valve stems of the steam cylinder and connecting in 
such a way as to permit adjusting the cut off of either steam or air valves sepa- 
rately. To make a closed system, pipes were driven into the quicksand at regular 
intervals, these, of course, having the bottoms closed. Air from the expansion 
cylinder was led into the bottom of these by means of small pipes and allowed 
to pass back up through the annular space between the inner and outer pipes 
thus absorbing heat from the earth around the large pipe. The connections to 
these pipes were made at the ground surface so that the air having fulfilled its 
mission was taken back to the compression cylinder. Between the compression 
and expansion cylinders a cooler was placed so that the heat of compression 
should be removed and incidentally the moisture precipitated before the air was 
expanded, this insuring a low temperature after expansion. The air com- 
pression and expansion cylinders were proportioned with the idea of having 
their pressures in a ratio the same as for the Allen Dense Air or Roelker System, 
namely, 210 to 225 pounds at the end of compression while after expansion and 
hence in the circulating line about 65 pounds pressure, A priming pump was 
used for charging this line and supplying air lost by leaks. 

This outfit was on trial for a period of several weeks, the temperature of 
the circulating air ranging from zero to 15 degrees F. The results of freezing the 
quicksand were not all that could be desired for it was found that there was an 
underground stream of running water passing around the refrigerating pipes 
which on account of its quantity would not permit freezing. Because of this 
water, it was concluded that it would be impossible to do the work by freezing 
and the idea was abandoned and a coffer-dam constructed instead. 

It will be noted that the temperatures given above do not compare very 
favorably with 60 to go degrees below zero, as obtained on shipboard. This is 
readily accounted for, however, by the fact that the installations on shipboard 
are permanent and therefore set up with greater care in respect to non-conducting 
transmission pipes, less leaks, etc., than for temporary use only. 

Some difficulty was found in the freezing of the moisture of the air in the 
expansion cylinder. This was largely due to the leaks in the refrigerating line 
which necessitated priming the system frequently with fresh air and consequent4y 
introducing moisture meanwhile. On shipboard the lines are so tightly con- 
structed that very little priming has to be done and the small amount of moisture 
is removed by traps. Devices for removing water from the line were also used on 
the Speedway work, but it was not brought to the state of perfection it doubtless 
would have been had the effect of running water not made it advisable to take 
recourse to some other means of doing the excavating. 



USE. ion 

The non-success of this particular case should not permit us to conclude 
that the idea is not a feasible one for it is sure to have its field in places where it 
is found necessary to freeze ground at extreme depths where it would require a 
large power to handle brine, while air would set up a circulation due to the 
unbalanced condition of the warm ascending and the cold descending columns ol 
air. 



SAND BLAST METHOD. 



SAID TO BE THE BEST FOR CLEANING SHIPS. 

The test of the new sandblast method for cleaning the hulls of ships, made 
at the Navy Yard last week, will in all probability be followed by the introduc- 
tion of the system into the different naval stations of the United States. The 
experimental tests on the bottom of the cruiser Atlanta, fully demonstrated the 
advantages of the new system over the method of doing the work by hand, now 
prevalent in the various navy yards. Not only does the sandblast system remove 
all foreign matter from the hulls in much less time than it takes to do the same 
work by the present system, but it is also cheaper. Naval officers who investi- 
gated the tests of the sandblast method made at the yard, have expressed them- 
selves as greatly pleased with it and it is expected that the officials will recom- 
mend its adoption to the navy department. 

The method is not a new idea, having been in operation for some years in 
nearly all the large dock yards and naval stations of Great Britain. The system 
has been most successful there. The machinery needed is simple and compara- 
tively inexpensive, comprising a pneumatic air pump, which forces the com- 
pressed air through a hose. An arrangement is attached to the end of the 
hose by which fine sand is played into it. As the air is turned on the sand is 
played on the ship's bottom by the operator, who directs the stream to the points 
where cleansing is needed. 

The compressed air pump is of the simplest character, and furnishes a 
pressure of only fifteen pounds to the square inch. This is powerful enough, 
however, to drive away all foreign matter from the steel plates of the ship's 
bottom in a remarkably short space of time, and it leaves the steel plates polished 
and as smooth as if they had been rubbed with emory paper. Paint, rust, scales 
and barnacles disappear as if by magic under the blast of the sand from the 
hose, and the inventors of the new method claim that it is five times as quick 
as the old hand method of cleaning a ship's hull. During the tests of the sand 
blast on the cruiser Atlanta, which was in dry-dock undergoing repairs, a space 
of ten feet square was thoroughly cleaned and polished smoothly in a few min- 
utes. Hard paint, nearly one-eighth inch thick, was taken off with ease. 

Naval Constructor F. W. Bowles, Captain of the Yard, Higginson, and 
Equipment Officer, Captain Spcrry, were present when the experimental tests 
were made, and all three officers expressed themselves as greatly pleased with 
the result of the trials. Naval Constructor Bowles was especially impressed with 



IOI2 



USE. 



the showing made by the sandblast method and commended its efficiency for 
cleaning steel plates. An ejffort will be made by the proprietors of the sand- 
blast to introduce their apparatus into the naval service. 



CLEANING STRUCTURAL IRON BY SAND BLAST. 

The city of New York is now trying the experiment of cleaning structural 
steel by the sand blast. The One Hundred and Fifty-fifth street viaduct is a 
steel structure and is used as a roadway with walks on each side. It suspends 




FIG. 429 .SAND BLAST IN OPERATION. 



from Washington Heights across the Harlem River. At about the middle of the 
viaduct is the terminal of the Manhattan Elevated Railroad, and at this point 
there are almost continually one or more locomotives which throw out smoke and 
gases that ascend upward and radiate in the maze of trusses above. The effect 
of this has been to quickly destroy the paints that have been applied and to leave 
the surface of the metal exposed to the weather, and a consequent rapid deteriora- 
tion from corrosion. Four coats of paint have been applied in five years, and the 
necessity of doing something to protect the structure led to the experiment. The 
makers of the best paints are applying their best products side by side under 
equal conditions. The metal structure is cleaned in advance by the sand l)last. 
The apparatus employed consists of two air compressors and a Ward and Nash 
improved Sand Blast apparatus of three mixers. 



USE. 1013 

The free air delivered is nearly 400 cubic feet per minute, the pressure being 
maintained at about 20 pounds. The air is conveyed about 300 feet to an air 
receiver which stands near the sand mixing apparatus. The sand mixers are 
shown in the illustration. The sand is thrown in the hopper at the top and it 
finds its way down to the bottom of the mixer, where it meets the air, and the 
two commingled flow through a 13/2" rubber hose and is delivered through a cast 
iron nozzle with a hole 9-16 inch diameter. The sand and air pass through this 
tube at a velocity of over ten miles an hour. The operator holds the nozzle close 
to the surface to be cleaned and flying sand striking the scale and the paint 
which still adheres, loosens it and finally cuts it completely away, leaving the metal 
as innocent of covering as the moment it came from the foundry. It is abso- 
lutely and thoroughly cleaned. The metal now presents a perfect surface for 
painting, and painters begin work of painting every day at three o'clock in the 




FIG. 430 — SECTION OF STRUCTURE SHOWING SCALE AND CLEANED SURFACE. 

afternoon, the earlier part of the day having been consumed by the cleaners. Two 
nozzles are kept at work at the viaduct. Combined, they are able to clean 700 to 
800 square feet per day. There is a man for each nozzle, an engineer for the com- 
pressors and several men to carry sand and sweep and carry away refuse. Twelve 
tons of scale were taken off of the structure by means of a clean air blast before 
the sand was used. 

It is assumed that this thorough and careful process of cleaning will so 
prepare the metal that the paint will now be firmly set when applied, and that it 
will fulfill its mission of preservation. The cost of cleaning by this method has 
not yet been determined, and fuller accounts of this will appear in future numbers. 



THE SAND BLAST. 



A. R. Lynch, Foreman Painter of the P., C, C. & St. L. R. R., Dennison, 
Ohio, writes as follows to the Railroad Car Journal : 



IOI4 USE. 

In recent issues of the Journ<il I see that much attention is being given 
to compressed air in its many and varied uses. It enters largely into the workings 
of the up-to-date paint shop. One of the best uses we have found for it at Denni- 
son is the sand blast for removing old paint, scales, rust, etc., from locomotive 
tanks. I was at the convention at Old Point Comfort, but was not present during 
the discussion of this subject, and I was not a little surprised, and regretted very 
much to learn that the sand blast process did not have a greater number of friends 
and more enthusiastic support than it seems to have had. It certainly deserves 
the consideration of any one who has locomotive tanks to paint. We have been 
using it for about eighteen months, and it has cost us, on an average, $2.50 per 
tank — some tanks being hard and some easy to blow off — but should it cost twice 
that much I would consider the operation cheap, for all our tanks that have been 
treated with the sand are in excellent condition, showing no sign of rust or scales, 
and after having been in service over a year can be put in as good repair as new 
by cleaning and giving one coat of engine finish and relettering (or "cut-in" if 
you choose). This makes a saving of about $10 as compared to the usual way of 
repainting tanks. Considering the thoroughness of the cleaning and the durability 
of the work which follows, we are led to believe that there is no method so per- 
fect and economical for removing old paint, scales and rust from tanks as the 
sand blast. At our shop the sand blast has come to stay, and after we have once 
gone over our tanks we will have no trouble with scaling or rusting nor any need 
ot a "rust killer." 



THE SAND BLAST PROCESS AS APPLIED TO THE CLEANING OF 
THE WALLS OF PARDEE HALL, LAFAYETTE COLLEGE. 

After the walls of Pardee Hall, Lafayette College, left standing from the 
fire, had been inspected and pronounced safe for rebuilding, the problem arose as 
to how the smoke stains on them could be removed. 

Various plans suggested themselves as to the cheapest and most effective 
manner of accomplishing this, but to the recommendation of Mr. W. S. Ayer, 
C. E., '72, was due the final adoption of the sand blast. The application of the 
sand blast to glass cutting and to cleaning castings is very common, but it had 
never been applied to the cleaning of stone walls and its usefulness for this pur- 
pose was largely a matter of conjecture. 

The air compressor and receiver for the operation were loaned to the col- 
lege by the Ingersoll-Sergeant Drill Co., from their works at Easton, Pa. 

The compressor was supplied with steam from a 10 h. p. vertical boiler 
belonging to the college at a maximum pressure of 50 lbs. The compressor was 
one of the company's direct acting type having a 10'' x 10" steam cylinder and a 
10" X 14^" air cylinder. The cylinders are directly in line, the piston rods being 
connected to a common crosshead. To each side of the cross-head are attached 
connecting rods which drive a pair of fly-wheels rotating on a shaft immediately 
in front of the steam cylinder. On the same shaft are placed two eccentrics for 
actuating the Meyer's expansion valve in the steam chest. 



USE. 



1015 



Air is supplied to the air cylinder through a pipe running through a 

iffing-box in the rear end of the air cylinder. This pipe leads to an air cham- 

;r in the piston from which air is alternately allowed to pass into opposite ends 

of the cylinder. This is accomplished by means of a pair of valve rings on the 

piston. The action of these rings is shown by the sketch. 

A and B represent the rings on each end of the piston in section. When 
the piston moves to the right B is in and A out, compressing the air to the right 
of the piston and admitting it to the left. When the piston reaches the end of 'ts 




FIG. 431 (LEANING STONE WITH SAND BLAST. 



Stroke and stops, the momentum of the valve rings throws B open and shuts A. 
On the return stroke the air pressure holds them in these positions and the opera- 
tions are reversed. Holes are cut in the webs of the rings through which pins 
are run, limiting the motion of the rings to about K" in this machine. 

The advantage claimed for these valves over the spring valves in ordinary 
use is that they remain open during the full length of the stroke, enabling the 
compressor to get a full cylinder of air at the atmospheric pressure,; while the 
spring valves, requiring a difference of pressure between the outside air and the 
interior of the cylinder to keep them open, supply air at less than the atmospheric 



ioi6 USE. 

pressure and are apt to close before the end of the stroke, when the piston is 
running slowly and the influx of air very small. 

The air is discharged through special check valves placed at the ends of 
the cylinder whose action will be explained later. 

The compressor is furnished with a regulator to take the load off the air 
piston when the pressure in the receiver reaches a given point, and at the same 
instant, to throttle the supply of steam to a point just sufficient to keep the com- 
pressor turning over. When the pressure goes down past the limit usually eight 
or ten pounds below the running pressure, the load is thrown on, the steam again 
admitted and compression is resumed in the regular way. 

The regulator which accomplishes this consists essentially of a weighted 
piston (the cylinder in which it acts being connected to the receiver) connected 
to a small slide valve. From the regulator, pipes are run to the discharge valves 
at each end of the air cylinder and to a throttle valve in the steam pipe. 

Normally the weighted piston is down and the pipes leading from the 
regulator to the discharge valves and to the throttle valve are filled with air at 
receiver pressure. The result is that the air pressure back of the discharge valves 
causes them to act as check valves, letting air out but not into the cylinder, and 
the throttle valve is held open giving full steam pressure to the engine. When 
the air pressure rises above a limit determined by the weigh*: applied to the piston, 
the piston will rise, resulting in the air (which was under pressure in the pipes 
referred to) being exhausted. When this pressure is relieved the discharge valves 
are thrown wide open by the air pressure in the cylinder, and stay wide open, the 
result being, of course, that the inlet valve rings are held shut and the piston has 
receiver pressure on both sides, and moves back and forth in equilibrium. At the 
same instant the throttle valve closes to a point which admits just enough of 
steam to overcome friction and keep the engine moving fast enough to prevent 
centering. The extent to which the regulator throttle valve closes is regulated by 
an adjustable nut. 

From the air receiver the air was carried by a pipe to the third floor of the 
building and from thence by a hose to the portable sand blast apparatus. 

The sand blast apparatus was built and loaned to the college by Ward and 
Nash, of Boston, Mass. 

It consisted of a circular iron receiver with a funnel or hopper inside. 

Sand is fed into it through one valve while the air goes in through another. 
The funnel does not fit tight to the interior of the cylinder so that the air pressure 
above and below it are the same. The air passes through the end of the pipe 
and out through hose to the nozzle and the sand dropping down from the bottom 
of the funnel is carried with it. By means of a lever a slider is pushed in or 
out and the flow of sand regulated. 

The great disadvantage of the apparatus was that the air pressure was 
so great that the valve could not be opened when the machine was in operation so 
that the compressor had to be stopped whenever the apparatus had to be recharged 
with sand. In some of the machines manufactured by Ward and Nash, an air 
lock is introduced and this difficulty overcome. From the sand blast apparatus 



USE. 1017 

the stream of air and sand was carried through a three-inch hose to the wall and 
discharged upon it through a half-inch nozzle. 

The velocity of the sand was quite high and the bombardment of the 
particles cut away the discolored surface in a very rapid and satisfactory manner. 
The pointing between the stones was cut away but that had nearly all been cracked 
by the fire and would have had to be done over again at any rate. The sand stone 
arches and facing around the windows was cut away very rapidly and care had to 
be taken that the dressed edges were not spoiled. 

The sand used was the best sea shore, clean and sharp. It had to be thor- 
oughly dried before using not only to prevent its caking in the machine but to im- 
prove its cutting properties. The sand after using was found to be worn quite 
round and smooth and was of little use for the same purpose again. The con- 
sumption of sand, however, was very moderate. Four buckets were required to 
charge the apparatus and this was sufficient to clean several yards of wall surface. 
Care had to be taken not to feed the sand too rapidly, otherwise the apparatus 
became clogged until the pressure rose high enough to drive out the sand, and 
then it poured out of the nozzle in a thick stream and at such a low velocity as to 
be useless for cutting purposes. 

The air pressure used was quite low, a pressure ranging from 12 to 15 lbs. 
per square inch proving most Effective. J. C. Heckman, '99. 



PNEUMATIC CAISSONS FOR ORDINARY FOUNDATIONS. 

At many places on our larger rivers it is so difficult to get first-class foun- 
dations, and keep other than first-class ones after once put in, that the only really 
safe way is to employ pneumatic caissons. For the ordinary large highway 
bridge as built by county or city, this is seldom considered, owing to the fact that 
comparatively very few officials having charge of this work know anything of 
pneumatic foundations, and until recently such work has been too expensive for 
bridges of this class. Pneumatic work has been made much cheaper by compe- 
tition and skillful handling, until for large highway bridges where good founda- 
tions are hard to get it is not only the best method, but almost as cheap as pile 
foundations. When the pneumatic caisson foundation is completed there is no 
question as to its stability, and no future expense for protection to hold it. A 
well built bridge on this foundation is for the use of generations to come, and, 
unlike many bridges on other foundations, will not need replacing before the 
present generation has passed away. 

A recent experience with a bridge on the Scioto River is a good example 
of pneumatic work for highway bridges. In 187 1 the County Commissioners of 
Ross County, Ohio, built a bridge across the Scioto River at the old ford at the 
foot of Main Street, Chillocothe. 

It has been with great difficulty that all previous foundations for Scioto 
River bridges in Ross County had been put in by use of cofferdams, owing to the 
river gravel being very coarse and full of bowlders, and, taking this into con- 
sideration, it was decided to adopt the pneumatic foundations, as being the surest 
and safest plan, and certain to reach bed-rock no matter what might be encoun- 



ioi8 



USE. 



tered. A few days after bids were received, the contract was awarded to Willard 
& Cornwell to construct two masonry piers on pneumatic caisson foundations, 
with crib filled with concrete to within five feet of low water, according to plan 
shown. On August 12th work was begun on setting up the air-compressor and 
getting ready for caisson No. i. The contractors' plant for this work consisted 




FIG. 432 — CAISSON NO. 3 BLOWING SAND. 



of a double compressor with cylinders 14x16x18 inches, run by a boiler of locomo- 
tive type capable of generating 120 horse-power; a 115-volt dynamo of nine 
amperes capacity, run by a vertical engine supplied with steam from the big 
boiler; an air receiver fifty-six inches in diameter and fifteen feet long, and all 
necessary pumps, pipes, connections, fittings, etc., with hoisting engines, derricks, 
mortar boxes, tools and everything necessary for heavy masonry and concrete 




USE. 1019 

k. The compressor and boiler were set up on the solid roadbed, a few feet 
west of the old abutment^ the compressor being next to the abutment, the boiler 
immediately west, and the dynamo and engine, for generating electricity for light- 
ing the caisson, engine-house and office being in the same building and just south 
of the compressor and boiler, the whole being covered by a substantial frame shed 
18x36 feet. An office, 10x12 feet, adjoins this building on the east. The receiver 
was placed north of the compressor, on the edge of the fill. A driven well at the 
foot of the embankment on this side, with a force pump, supplies water for the 
boiler and drinking water for the men. An eight-inch natural gas main runs 
within 1,000 feet of the engine house, and an inch pipe was laid from it and con- 
nected to the boiler to supply fuel for generating steam. 

Both caissons were built exactly according to plan, twelve feet wide by 
thirty-two feet long and six feet deep inside, and sheeted inside and out with 
two-inch plank. The sides and roof of the caisson are two feet thick, built of 
I2xi2-inch timber, each course being fastened to the courses below with ^ and 
^-inch drift bolts, thirty inches long and placed four or five feet apart. The 
two courses of the sides and ends are firmly fastened together by two rows of 
^-inch bolts extending clear through both. The two bottom layers of timber are 
beveled ofif on the inside until only about four inches wide at the bottom, and on 
the bottom a 2x6-inch plank is firmly spiked, forming the "cutting edge" of the 
caisson. Two I2xi2-inch tie-beams are dovetailed into the sides of the caisson, 
thus dividing the inside into three equal "pockets." There are five holes through 
the roof, a four-inch hole at the centre of each end "pocket" for the blow-out 
pipes ; in the middle pocket an 18-inch hole near one beam and a 20-inch hole near 
the other beam for the supply pipe and air shaft, respectively, with a 4-inch hole 
near the latter for the air supply pipe. When one course of the roof is placed, 
the shafts are fastened on by means of bolts through this course and the flanges 
of the shafts. The air shaft is thirty-six inches in diameter, of the best ^-inch 
boiler iron, thoroughly riveted together at the lap joints and to inside flanges 
of i^-inch cast iron at each end, each flange having twenty-eight %-inch holes 
for bolts to fasten joints together. The flanges are on the inside, so they can be 
used for the lock doors to fit against, and the bolts being on the inside can be 
removed and the top sections of the pipe taken out when pneumatic work is 
finished. The supply pipe is eighteen inches in diameter, of the same material 
as the air shaft, and 3-16-inch thick. It is riveted together the same as the air 
shaft, except that the cast flange is on the outside and has but eighteen holes for 
bolts. These shafts are in joints varying from nine to fifteen feet in length. The 
timber used in caisson walls in crib and outside sheeting may be any good round 
timber in lengths of ten to twenty-four feet. In this work hickory, lynn, syca- 
more, red oak, etc., were used for all work except inside sheeting, which was of 
dressed pine. The inside of the caisson, from the cutting edge to the roof, and all 
over the roof, was caulked carefully in each joint between the timbers and around 
all bolt heads, then sheeted from bevel edge to roof and overhead, every joint of 
the sheeting being thoroughly caulked. Caisson No. i, which was to go in the 
middle of the river, was built on timber runways on the bank, arranged so they 
could be raised at one end and slide the caisson off into the water when it should 
be rea^ to launch. Two heavy ropes were placed around the caisson and tied 



IO20 USE. 

to posts behind, the runways were covered with soft soap, and the ends raised 
until the caisson was started and held only by the ropes, which were cut simul- 
taneously, and the caisson slid out into deep water and floated with the top but 
little above the surface. On September 8th it was launched, towed into position, 
and anchored by ropes leading to some old piles at one side, and to a heavy 
anchor and a piece of old bridge iron up stream. When launched, but one course 
of roof or decking had been put on, and as soon as anchored to place the other 
course was put on and the crib on top built up several feet. This cribbing is of 
I2xi2-inch timber, laid so as to make the outside of crib twelve feet by thirty- 
two feet, every other course tied together by two I2xi2-inch cross ties dovetailed 
in, and the whole fastened together with thirty-inch drift bolts every four or five 
feet. The sheeting is also carried up continuous on the outside from the cut- 
ting edge. The top of the decking was then thoroughly grouted, the crib filled 
with concrete to the height of several feet, until the "cutting edge" rested on the 
river bottom and the top was four or five feet above water. This concrete was 
composed of one part Portland cement, two and one-half parts sand, and five 
parts gravel, with a good many large bowlders bedded in each layer. A three- 
inch pipe was laid from the receiver down the bank and along the river bed to the 
pier, and connected to the air supply pipe by a double flexible pipe joint. At noon 
of September 12th air was turned on and the work of sinking was carried on day 
and night by two crews, each working ten hours. Each crew of "sand-hogs," as 
the men engaged in this work are called, consists of a foreman, two blow-pipe 
feeders, four shovelers, an inside lock-tender and an outside lock-tender. The 
working chamber is lighted with three sixteen-candle power electric lights, and 
there is one in each section of the air shaft. The blow-out pipes just below the 
roof of the caisson are fitted with large valves with a four-inch opening. A piece 
of pipe from the valve extends to the bottom of the caisson, and when the valve is 
opened all sand, gravel and rock less than four inches in diameter brought up to 
the end of the pipe is forced out by the air pressure. On the top of each blow-out 
pipe is fastened a "goose neck," a curved joint to turn the material away from the 
crib. This "goose neck" is cast iron, with a four-inch opening and heavy walls, espe- 
cially on the upper side where the gravel strikes, for it comes out with such force 
that an ordinary pipe bent to a curve would last but a few hours. All rock too 
large to blow out through the pipes is "locked" out through the air shaft in 
sacks. To sink the caisson all material is cleaned out level with the "cutting 
edge," then it is "ditched" by shoveling several inches of material from under 
the "cutting ed^e" and given a "blow" by opening one of the valves and letting 
out the greater part of the air. Relieved of the lift of the compressed air, and 
with the weight of concrete on top, the caisson settles down from six to ten 
niches, or until the cutting edge is again on solid gravel. While the air is escap- 
ing the working chamber is filling with water, and will frequently be two-thirds 
full when done "blowing." Caisson No. i, for eighteen or twenty feet below 
the bed of the river, went down smoothly and rapidly without delay. At this 
depth was encountered a layer of bowlders varying in weight from five pounds 
to over one hundred pounds, and at the bottom of the layer were three coping 
stones from the top of the old east pier, which had been washed out. These 
stones were thirty feet below low water and sixty-six feet from where fhe pier 



USE. I02I 

had stood showing how deep the scour had been when the water was highest. 
As the water fell and the current became less swift, the larger rock coming down 
were deposited, and then the smaller rock, gravel and sand. This layer of rock 
was what had stopped the sounding rod, but immediately below was six or eight 
feet of quicksand, and then another layer of gravel and rocks, but bed rock was 
not struck until forty-three feet below low water. The bed rock consisted of 
black shale and limestone in alternating layers of about two inches in thickness. 
The caisson was landed and rock leveled down after twenty-three days' work, 
and on the morning of October 6th concreting the air chamber was begun. To 
concrete the air chamber a two-inch pipe connection is made from the air pipe to 
a point just below the top flange of the supply pipe. This pipe has a valve. No. i, 
near the air pipe, and another valve. No. 2, on a T between valve No. i and the 
supply shaft. A top door opening down is then put on the supply shaft and the 
fastening taken off the lower door. A batch of concrete is shoveled into the 
supply pipe, the upper door pulled up, valve No. 2 closed and No. i opened. 
This puts compressed air in the supply shaft and allows the lower door to equalize 
open and the concrete falls into the working chamber, where it is rammed under 
the bevel edges and over the bottom by the "sand hogs." The lower door is then 
shut, valve No. i closed and No. 2 opened, allowing the compressed air in the 
supply shaft to equalize out and the top door opens. The process is repeated 
until the chamber is filled with concrete and barely a narrow passageway for one 
man is left between the lower doors of the supply shaft and air shaft. The 
lower doors are then shut, and the last man equalizes out. A regular air pressure 
is then kept on for twelve or eighteen hours, until the concrete sets. The air is 
then turned off, and the shafts filled with concrete as quickjly as possible. As 
soon as the air pressure is taken off the lower doors drop and the space left in the 
working chamber is also filled with concrete, which runs in from the shafts. 
This finishes the foundation from bed rock to above low water. 

Caisson No. 2 was built about ten feet back of the washed-out abutment, 
part of the old approach- being leveled down to near low water mark so it could 
build exactly where it was to sink, and at noon of the 14th day of October, air was 
put on caisson No. 2. This caisson was above the water level, and before put- 
ting on air it had been sunk about two feet. As the pressure at first would be 
low, temporary blow-pipes were put in the side near the roof, and used to blow 
out sand and gravel until they were down to water level. This required less air 
to blow out material than to lift it through the roof. When down to water level 
these pipes were removed and the holes plugged. This caisson went down with- 
out special incident until the "cutting edge" was about fifteen feet below low 
water, when a good sized red oak tree was encountered. Several blasts were 
put into holes bored in the tree under the cutting edge, until the trunk was 
severed at this point. The tree was then sawed up and removed through the air 
locks. Dynamite was used to blast out this tree, and also to blast to pieces lafge 
stone found in the caissons. When blasting the men stayed in the air shaft, 
and frequently in the working chamber itself, for the concussion from a blast is 
not felt under air pressure as it would be on the outside. Test rods were driven 
at several points inside, and there was apparently a level bed rock about twenty 
feet below low water. Accordingly on October 8th the cutting edge being about 



1 



I022 USE. 

five feet from the bottom of the rods, the first footing course was laid, and the 
next day the second course offset six inches all around, making it 11x31 feet. 
According to the rods, we were then about two and one-half feet from bed rock. 
The "sand hogs" now attempted to pull the ^^-inch sounding rods which had been 
cut off as the caisson was sunk, and found they could not move them, although 
but two and one-half feet were in the ground. They even broke a large chain 
by using leverage to pull on the rods — we then had them dig down at one point, 
and they brought up a sample of a peculiar material that was neither peat nor 
lignite, although it was evidently the bottom of an old swamp. The material was 
tough and like rubber when a pointed rod was driven into it, but a piece taken 
out proved to be brittle and of no strength. We now drove rods through it and 




FIC. 433 — FLASHLIGHT IN CAISSON. 



found that after two or three feet they again drove part of the way, with great 
ease, until striking bed rock on a level with bed rock under caisson No. i. It was 
decided not to land the caisson on the lignitic peat, as there was evidently quick- 
sand under this layer, and the sinking was continued. This material was hard 
to work, and the "sand hogs" were seven days making two feet in depth. The 
first course of stone, and part of the second, was below water before it was de- 
cided to continue, and therefore the 11x31 feet of masonry had to be brought 
on up. A great many difficulties were encountered in sinking this last twenty- 
two feet, and it was not completed until November 30th. The compressor broke 
down twice, and high water got above the masonry and stopped the work once 
for several days. The first footing course dragged considerable and held back 



USE. 1023 

the caisson in sinking, and the ends at different times were as much as a foot out 
of level. In bringing the pier back to a level, several of the joints in the masonry 
were opened, but no stone cracked. Below this lignitic peat the sand and gravel 
was of a different character than that above, or what was encountered in sinking 
caisson No. i. First there was eight or ten feet of sand almost as fine as quick- 
sand, and working like quicksand, then the rest was coarse gravel with bowlders. 
This sand and gravel was dark, but contained but little soil, the color being given 
by hornblende and other dark rock in the drift. Within a foot of the bed rock 
was found a skull, which proved to be that of a pre-glacial hog. The lignitic 
peat is a formation of the glacial period. 

Pier No. 3 was to be erected"iS4 feet east of the river, to hold the end of an 
approach span which was to take the place of that much embankment. One of the 
spans of the old bridge was repaired for this approach, and it was oriniganlly in- 
tended to use four-foot tubes sunk to solid foundation to hold the east end, but 
when bids were received the bid of $2,goo was made for a pneumatic caisson sunk 
to twenty feet below low water, with masonry pier. The bids for the tubes were 
from $1,012 to $2,200, and the Commissioners at first awarded the contract to the 
lowest bidder on tubes, but within three weeks the sinking of caisson No. 2 
proved what difficulties might be encountered in sinking tubes and possibly result 
in failure, and the bidder on tubes willingly consenting, the contract for pneumatic 
caisson was awarded to the contractor who was building the other two. This 
caisson was built ten feet four inches by twenty-seven feet four inches on the out- 
side, with walls of 10 x 12-inch timbers, making the inside twenty-three feet eight 
inches by six feet eight inches. Temporary blow-pipes near the roof were also 
used in sinking caisson No. 3, this time being placed in the ends. On December 
I2th air was turned on No. 3, and it was sunk through a layer of drift gravel, a. 
layer of loose rocks, and a layer of quicksand, and landed on the lignitic pe«" 
nineteen feet below low water, and the concreting was completed on December 
28th. High water delayed work on this caisson four days, breaking the air pipe 
in the middle of the river. This completed the pneumatic work, and the masonry, 
having been kept up pretty closely, was completed on January 6, 1899. All 
masonry work was of heavy freestone rock from Otway, near the Ohio River, in 
Scioto County. Three thicknesses, seventeen inches, twenty-one inches, and 
twenty-eight inches, were used. The masonry was quarry- faced, with full dressed 
beds and laid in Portland cement mortar mixed in proportion of one part cement 
to two parts sand. No grouting was used except in holes too small to ram con- 
crete in, the backing being of stone placed far enough apart to allow concrete to 
be rammed in solidly between. Piers No. i and No. 2 are shown in the plan 
while pier No. 3 was lighter, being but twenty-four feet long by five feet three 
inches wide under the coping, and built with square ends. It being in place of an 
abutment, the earth fill is given a natural slope at the ends and in front of the 
masonry. 

Many persons were allowed to go down in the caissons to see the process ot 
working. For the trip they were fitted out with overalls, jacket, an old hat and 
rubber boots. The top door of the air-lock or shaft had a rope fastened in the 
ring to handle it by when the air was off. When the door was closed and the air 
pressure on several tons would be required to open it by force, hut as soon as 



I024 USE. 

the signal was given — five taps with the hammer by the outside lock-tender — and 
answered by the tender inside, the valve would be opened and the air allowed to 
escape, the door at the bottom having been previously closed, and when the air 
pressure was all off the top door would drop. The lock or shaft is a dark, for- 
bidding-looking place, full of a fog which soon clears out, disclosing an iron 
ladder down one side and electric lamps for light. After going in, the top door is 
pulled up by the outside tender, and the pressure pipe opened. As soon as the 
pressure becomes considerable, the novice becomes "plugged," owing to the pres- 
sure on the ear drums pressing them in, but by holding the nose with thumb and 
finger, and with the mouth closed, a hard blow from the lungs, with distended 
cheeks, presses them out again, and relief is had. This can also be overcome by 
placing the ears close to the outlet pipe and opening the valve. \^'^hen the pres- 
sure in the lock has become equal to that in the working chamber, the lower door 
drops, and the caisson can be entered. Owing to the excitement and the thought 
of what might happen, the perspiration comes easy, but the temperature is very 
little higher than outside. The blow-out pipes extend to the bottom of the end 
pockets, and when opened the sand and gravel rush to the end of the pipe like 
tacks to a magnet. Some air escapes with the gravel, the air becomes foggy, 
and the water comes in to a depth of six inches, or more ; then the blow-out is 
closed until the air clears, and the water is driven out. The end of the supply pipe 
is curved and provided with a flap valve, which would close at once in case the 
supply pipe across the river broke, or the air was shut off in any way. 

To sink the caisson the "sand hogs" dig out under the cutting edge, which 
process is called ditching, then the air is allowed to partially escape, and the cais- 
son sinks or drops down. The chamber becomes foggy and half fills with water, 
but when the compressed air comes in strong again it clears up and the water is 

expelled. 
c 

The bid in detail upon which this work was awarded is as follows : For 

pneumatic caisson and crib filled with Portland cement concrete, on a basis of 
thirty feet or less below low water for pier No. i, and twenty-four feet for pier 
No. 2, top of both cribs to be five feet below low water, $8,300; for rock, slate, 
logs, or bridge iron removed through locks, $9 per cubic yard; for excavation in 
slate or bed rock requiring blasting, $7 per cubic yard; for extra depth to forty 
feet below low water, $150 per lineal foot; for extra depth forty to sixty feet be- 
low low water, $160 per lineal foot; pier masonry, $7.25 per cubic yard. This was 
$12.77 per cubic yard of caisson and crib, not including rock, etc., that might be 
locked out, and $10.16 per cubic yard for extra depth to forty feet below low 
water. For pier No. 3 caisson and crib sunk to twenty feet below low water and 
filled with Louisville cement concrete, $1,600; for all material locked out. $193; 
for abutment masonry, $6.75 per cubic yard. This is $11.47 per cubic yard of cais- 
son and crib, including all locked out material. Pier No. i was sunk 13.15 feet 
extra depth, and No. 2 18.68 feet extra depth, costing $4,832.80. Twenty-five 
cubic yards of rock was locked out of No. i, and eighty-two cubic yards out of 
No. 2, at a total cost of $988.20, making Pier i and Pier 2 within five feet of low 
water cost $14,121, or $12.61 per cubic yard. The total amount of masonry in 
piers No. i and No. 2 above the level of five feet below low water, 498.73 cubic 
yards, and cost $3,615.79, or a total of $17,736.79, or an average for two piers en- 



'SF' 



USE. 1025 

tire of $10.95 per cubic yard. The contractors obtained most of the material and 
labor at very reasonable prices. For timber $11 per 1,000 feet B. M. ; for sand, 
gravel and bowlders, 25 cents per yard ; for stone, $3.35 per cubic yard, delivered 
at bridge site; for Portland cement, $2.15 per barrel, all delivered at bridge site. 
Ordinary labor was $1.25 per day; the cost of other labor was from $1.50 to $2.00 
per day, except stone-cutters, who received 25 cents per hour; foremen received 
from $2 to $5 per day. 

We have adapted the above from an article published in Bridges and 
Framed Structures by A. W. Jones. 



THE PNEUMATIC CAISSON FOUNDATIONS FOR THE BROAD-EX- 
CHANGE BUILDING, NEW YORK CITY. 

The Broad-Exchange Building, now under construction at the corner of 
Broad street and Exchange place, in New York City, will be the largest office 
building in the United States. It will be 23 stories, or 286 feet, high above the 
street, and will cover an irregular area of about 27,000 square feet, with front- 
ages of 236 feet on Exchange place and of 106 2-3 feet on Broad street, and with 
a wing about 100 feet long and 35 feet wide extending south toward Beaver 
street. The exact dimensions of the ground plan are shown by Fig. i. Alto- 
gether there will be 10,000 tons of steel employed in the framework, which will 
be enclosed with walls of granite to the top of the first story, of Indiana limestone 
to the top of the third story, and of brick and terra cotta for the remainder of the 
height. The framework will be carried by 100 lines of columns, each founded on 
a separate steel caisson sunk either to bedrock or to the hardpan overlying it. 
The large number of caissons which were sunk and the extreme celerity with 
which, under the conditions, this work was done, make the foundation construc- 
tion of particular interest, and we present here a description of the apparatus and 
methods of work employed. 

PRELIMINARY WORK. 

The foundation work of the Broad-Exchange Building is of interest, not so 
much for its character, which was not particularly novel, as it is for its extent 
and for the difficulties which resulted from the short time available for carrying 
it out. To make these matters clear it is necessary to set forth the actual condi- 
tions in some detail. 

The Broad-Exchange Building is being built for a syndicate of New York 
capitalists, the general contractors being the George A. Fuller Company, of New 
York City. The contract called for the completion of the building ready for the 
tenants by May i, 1901. On May i, 1900, the work was placed in the hands of 
Clinton & Russell, of New York City, as architects, and of Purdy & Henderson, 
of New York City, as structural engineers. So far as actual construction was 
concerned, therefore, the condition of affairs was that not a line of the plans had 
been placed on paper twelve months previpvis to the day set for the tenants to 
move into the building. Evidently the utmost haste was imperative. Further- 



1026 



USE. 



more, it must be remembered that this haste was necessary at a time when the 
rush of work had placed all of the large steel mills behindhand with their orders, 
and that large quantities of steel work were the first materials needed for the be- 
ginning of construction. 

The problem was a twofold one; plans had to be prepared in a remarkably 
short time, and the methods had to be devised to secure the manufactured mate- 
rials to put these plans into material form in the building. Under ordinary condi- 




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FIG. 434 — FIRST FLOOR PLAN OF BROAD-EXCHANGE BUILDING, NEW YORK CITY. 



tions the engineers would have waited until the architects had settled upon at 
least the general lay-out of the building before beginning work, but to follow this 
precedent in this instance would have necessitated a delay which, although it was 
short, neither they nor the architects were disposed to endure patiently. Accord- 
ingly the engineering studies were begun without knowing at all what the final 
plans of the architects would be. It is obvious that these studies had to be in a 
great measure of a tentative character. 



USE. 



1027 



The first act was to adopt a tentative plan calling for 106 lines of columns, 
|and to estimate and assume the column loads. This woric gave something of a 
definite basis upon which to begin studies of a foundation plan. The general 
contractors had had in mind using pile foundations, but before adopting this con- 
struction it was decided to make a comparative study of several types of construc- 
tion. The next work, therefore, was to design and to estimate the costs and rela- 
tive advantages of pile foundations, foundations consisting of steel cylinders filled 
with concrete, and of foundations consisting of pneumatic steel caissons filled with 
concrete. As the result of these comparative studies a report was presented on 
May 23, in which the use of pneumatic caisson foundations was advised. The 
decision was accepted by the general contractors and, stated briefly, was influenced 
by the following considerations : 

(i) By using pneumatic caissons comparatively certain results in the time 
required for the work were ensured. Some of the material penetrated was ex- 
ceedingly unstable; it was quite certain that pneumatic caissons could be sunk 




FIG. 435 — SKETCH PLAN OF EQUALIZING GIRDER SYSTEM FOR COLUMNS 78, 79 AND 80. 



through this material without danger of unforeseen delays, but there was no such 
certainty if either of the other forms of construction were adopted. (2) By using 
pneumatic caissons the good character of the foundation work could be ensured 
beyond a doubt, and this was not possible if eilher of the other constructions was 
employed. (3) The reputation of pneumatic caisson foundations for excellence 
was considered to be a material advantage to the builders and owners from a 
business standpoint. There was also another consideration which influenced the 
selection of pneumatic caissons, and this was that whatever style of foundation 
might be adopted for the other columns, those coming on the party lines would 
have to be founded on pneumatic caissons in order to prevent disturbing the 
foundations of the adjacent buildings. 

With the consent of the general contractors to the use of pneumatic caisson 
foundations, one factor of the problem has been disposed of. By this time the 
architects had determined in a general way the lay-out of the building, and it was 
possible to decide approximately upon the number of columns to be employed. It 
was not possible, however, to locate these columns definitely, and hence their 



I028 USE. 

exact loading could not be calculated. From the data available, however, two 
things were certain : ( i ) that the number of columns to be provided with foun- 
dations would be at least lOO, and (2) that the loads on these columns would run 
between a certain maximum and minimum. Obviously, therefore, if a typical 
caisson should be designed which could be made in a number of sizes between 
those required for the known maximum and minimum loads, it would be possible 
to order a number of each size in advance of definite knowledge where each was 
to be located, and yet with the certainty that they could all be used somewhere. 
There was very little risk in such a mode of procedure, and the gain in time of 
manufacture which made it possible was an important advantage. 

The column caissons were, therefore,, divided into two classes. The first 
class comprised the caissons for the wall columns on the party lines, which re- 
quired special design in each instance, and could not, therefore, be designed until 
the location and loading of the columns which they were to carry were definitely 
known. The second class comprised all but a few of the columns not coming on 
party lines, and for which a typical general design of caisson was possible. The 
typical design of caisson adopted was a cylindrical caisson of steel ; the diam- 
eters were fixed at 7, 7^, 8, 8^, 9 and 9^/2 feet. The next step was to secure 
some one who would manufacture these steel caissons quickly. To obtam im- 
mediate manufacture and delivery by any of the large steel works was found to 
be out of the question, and a search was begun among the smaller concerns cap- 
able of handling the work. This search proved unusually successful. A contract 
was made with the Lukens Rolling Mill Company, of Coatesville, Pa., to roll the 
steel sheets in three days, and with the Coatesville Boiler Works to begin the 
delivery of the caissons in ten days from the date that the steel sheets were de- , 
livered to them, provided they jivere furnished with the I-beam bracing, which they 
could not manufacture, at once and in shape ready for use. To secure the I-beam 
bracing the engineers went to a number of places where a small lot could be ob- 
tained, and to ensure its prompt delivery to the Coatesville Boiler Company,' a 
man was sent on the car with every lot to prevent any hold-up of the shipment 
by the railways. 

Shortly after the order for the manufacture of the caissons had been given, 
the architects presented a definite plan of the building. This plan enabled the engi- 
neers to begin the definite design of the steel work, and the plans were far enough 
advanced by the time the first delivery of caissons was made to enable them to 
be located at once, and the sinking begun. Before describing the work of sinking 
the caissons, the general character of the foundation construction and the details 
of the caisson construction will be described and illustrated. 

GENERAL PLAN OF FOUNDATIONS. 

The foundations were designed upon the general plan that each line of col- 
umns should have its individual caisson foundation. All the caissons except 
those located along a portion of the south and west party lines are cylindrical 
and carry the column footings concentric with their top. The party wall caissons 
are rectangular with their longer parallel to the party-line. As will be seen the 
cylindrical caissons vary from 7 feet to 9>^ feet in diameter, the greater number 
being of the smaller size. They are filled with concrete to the top, and most of 



USE. 



1029 



them also have a granite capping the full size of the caisson. The column bases 
are circular in plan and are bolted directly to the caisson masonry. 

In the case of the rectangular caissons the column loads are distributed to 
the masonry by means of I-beam grillages, as shown by the various sectional ele- 
vations. The most complicated of these distributing girder systems is that for 
the group of columns at the south end of the wing, an enlarged plan of which is 
sliown by Fig. 435. The two bays or panels between columns Nos. 78, 79 and 80 
have a system of wind bracing consisting of X-braces of channels. 

CAISSON CONSTRUCTION. 

Details of the caisson are shown by Figs. 436 and 437. Fig. 436 shows one of 
the 7-foot cylindrical caissons, but the construction of those of larger diameter is 
practically the same. Fig. 437 shows one of the rectangular caissons ; the others, 
except one, No. 98, which is of trapizoidal form, are exactly like this except in 
dimensions. All the caissons were built of medium steel 5-16 inch thick for the 
caisson proper, and % inch thick for the cofferdam portion. The caissons all 
have reinforced cutting edges and a working chamber 6 feet 6 inches high. The 
minor details of construction are clearly shown by the drawings. 



METHODS OF WORK. 

Borings made at ten different points over the foundation area showed first a 
layer of filling from 2 feet to 6 feet thick overlying a layer of fine sand and clay 
mixed, which extended to hard-pan at an average depth of about 40 feet below 
the street surface. The fine sand and clay mixed proved to be a very unstable 
material; when wet it ran almost as freely as water. The hard-pan was, how- 
ever, of the firmest and most stable character, being practically a rock, and direct- 
ly below it came the gneiss bedrock. Upon the showing made by the borings 
general instructions were drawn for the sinking of the caissons, which were, 
somewhat condensed, as follows : 

If the hard-pan over the rock is not more than 6 feet deep, the shaft should 
be open to the bottom and cleaned out, so that the concrete shall have a perfect 
bearing on the clean rock. If the rock is not more than about i foot out of level 
and the hard-pan is about 2 feet thick or more, the concrete can be placed directly 
on the rock. If the hard-pan is thin or there is none, and the face of the rock 
is generally even, it must be leveled off or cut or shaped in some way so that it 
will resist any tendency to lateral displacement. If the rock is very uneven it 
must be leveled off or channeled or fixed in some good way to afford a satisfac- 
tory footing for the concrete shaft, not only for the direct load it must carry, but 
also to resist any tendency to lateral displacement. 

If rock is not found after the excavation has been carried fully 4 feet into 
good hard-pan, drive a crowbar, in not less than two places, to locate the rock. 
If it is found within 2 feet excavate out the hard-pan to a secure l^earing on the 
rock. If it is not found, clean out a footing on the hard-pan over an area some- 
what larger on all sides than the size of the cutting edge of the caisson, as given 
in the schedule below : 



I030 USE. 

7-foot diameter must be excavated 8 inches more, all sides. 

yyi-ioot diameter must be excavated i8 inches more, all sides. 

8-foot diameter must be excavated 9 inches more, all sides. 

8^-foot diameter must be excavated 10 inches more, all sides. 

9- foot diameter must be excavated ii inches more, all sides. 

gyi-ioot diameter must be excavated 12 inches more, all sides. 

By this schedule of arrangement the bearing area of the caisson masonry was 
increased from 39 per cent, for the 7^-foot caissons to 49 per cent, for the 95^- 
foot caissons. 

The contract for the pneumatic work in sinking the caissons was awarded to 
the Engineering Contract Company, of New York City. The general contractors 
located the caissons, set them up ready for sinking, furnished the concrete, and 
supplied the derricks and hoisting machinery; the Engineering Contract Com- 
pany furnished the compressed air, the steam power and the labor, and sunk the 
caissons and placed the concrete under pressure. The concreting in the open was 
done by the general contractors. The engineers checked the location of the 
caissons and watched that they were kept plumb. The engineer in charge also 
went into each caisson to see that the excavation had been properly finished and 
also supervised the placing of the concrete. With this brief explanation of the 
apportionment of the work, it will be described as a single task to avoid con- 
fusion. 

The bottom of the foundation excavation was about 15 feet below the street 
surface, and at the level of the street surface a strong timber platform was built 
covering the whole area. The caissons and all structural material for the foun- 
dations were unloaded onto this platform, and it also carried the power plant and 
machinery. Chutes, stairways and traps at various points in the platform allowed 
the materials to be sent below as they were needed. 

The air compressor plant for the caisson work consisted of two 16-24 X 12-18- 
inch Ingersoll-Sergeant air compressors, supplied with steam by a 4-inch pipe 
from the mains of the New York Steam Company, These compressors delivered 
into a 6 X 18-foot cylindrical receiver. To cool the compressed air for delivery 
to the caissons, two methods were employed. When at the beginning of the 
work no more than four caissons were being sunk at once, it was found possible 
to keep the air below 80 degrees F. by pumping cold water through the receiver. 
At a later stage of the work when as many as ten caissons were under way at once, 
an additional cooling device was employed which consisted of 54 pipes ^-inch in 
diameter contained in an 18-inch X 15-foot cylinder. The air from the com- 
pressors was passed through the pipes and cold water was kept in constant circu- 
lation through the cylinder. From the cooling cylinder the air passed into the 
receiver at a temperature of about 70 degrees F. 

For the first five or six feet of their descent, or to water level, the excava- 
tion inside the caissons was done in the open, and then air pressure was put on. 
As the sinking progressed the cofferdam of the caisson was added to, so as to be 
always above water level, and was filled with concrete around the central air 
shaft. The maximum air pressure used was 18 lbs. Generally the weight of the 
concrete in the cofferdam and a load of ten or twelve tons of pig iron were suf- 
ficient to sink the caissons. The caisson men worked in three shifts of eight 



USE. 



103 1 



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I032 USE. 

hours each, and there were nine gangs of six men in each shift. Each gang had 
three men in the working chamber, one man in the air lock and two outside. 
Air pressure was maintained at 30 lbs. in the receiver and was throttled down to 
the required pressure at each caisson. 

All the caissons were provided with 36-inch shafts, which in fhe majority of 
cases were divided diametrically by two inside angle guides. The bucket used 
was semicircular in plan, and worked up and down in one compartment of the 
shaft, while the other compartment contained a ladder and served as a main 
shaft. In other cases a cylindrical bucket 18 inches in diameter was employed. 

At first the concrete was mixed on the main platform near the caisson in 
which it was to be used. Later on two small platforms were built at central 
points about 10 feet or 12 feet above the main platform, and each of them was 
equipped with a balanced wheelbarrow-elevator running to the bottom of the 
main excavation. The cement, sand and broken stone were hoisted to the upper 
platform and mixed by hand. The mixture was then shoveled into a gravity 
mixer, which discharged onto the floor of the main platform. From the point of 
discharge the concrete was taken by wheelbarrows to the caissons. Pressure was 
maintained in the working chamber until the concrete was set, and then the air 
lock was removed and the cofferdam was filled and the capstone placed. The 
final work was the placing of the column pedestals. 

In conclusion it should be noted that 88 caissons were sunk in 47 days. The 
most rapid sinking recorded was 2 feet in one hour and 2^ feet in 20 hours. 



SINKING CYLINDER FOUNDATIONS IN VALPARAISO. 

The following account of an important application of compressed air is 
given in The Engineer. 

Amongst the works designed and executed in the Port of Valparaiso foi 
the Government of Chili in 1874-83 was a wrought iron mole or pier, for the dis- 
charge of ocean-going steamers of the largest class. 

The special circumstances of the case— the great depth of water at a short 
distance from the shore, and the proverbially severe storms of "Valparaiso North- 
ers" to which the work would be subjected to in the open bay — were the chief 
factors leading to the design for a pier which should present the least obstruction 
to the force of the storms, should be economical in construction considering the 
depth of water — ^42 ft. to 48 ft. — and should also possess the advantages of con- 
venience and permanence. In view of the conditions to be fulfilled, it was de- 
cided to build a pier of wrought iron girders, supported on fifty-two wrought iron 
cylinder foundations, 11 ft. 4 in. diameter, placed at equal distances and sunk a 
sufficient depth into the bottom of the sea to give them the required stability. 
They were to be filled with Portland cement concrete, and braced together by 
fender girders and the flooring of the pier. The superstructure was provided 
with hydraulic cranes for lifting ordinary merchandise up to i^ tons, and with 
one big crane capable of lifting exceptionally heavy weights up to 45 tons. 

But it is not the purpose of this article to deal with the work as a whole, but 
with the pneumatic method used in sinking the cylinder foundations. The pneu- 



r 



^^ 



USE. 1033 



matic apparatus used at Valparaiso was designed by the late Mr. John Hughes, 
M. Inst. C. E., at that time engineer-in-chief, who was well known in connection 
with this class of work from the time it was first used by him in sinking the foun- 
dations of Rochester Bridge in 185 1. As will be seen by the accompanying illus- 
trations, the latter form of apparatus presented many novel and interesting fea- 
tures. The cylinders themselves were formed of wrought iron, the bottom length 
of 15 ft. being riveted together in one piece. The first 5 ft. 6 in. from the bottom 
upwards was formed of two thicknesses of ^ in. plates riveted together, with 
rivets countersunk on the outside, and with the usual cutting edge at the bottom of 
the cylinder. On the inside were angle iron knees supporting a shelf 5 ft. from 
the bottom, and closing an annular space between the outside cylinder, which 
was II ft. 4 in. internal diameter, and an inner cylinder 8 ft. in diameter, thus 
leaving the annular space exactly half the area of the whole cylinder, or 50 square 
feet. When this space was afterwards filled in with concrete, weighing approx- 
imately twice the weight of water, it was sufficient to balance the cylinder and 
compensate for the buoyancy created by the exclusion of the water by the com- 
pressed air. 

The inner cylinder was made of J^-in. plates and the outside with the cit- 
ception of the bottom 5 ft. 6 in., was made of 3/^-in. plates, riveted together ana 
stiffened with angle iron rings. With the exception of the bottom length of is 
ft. the outer cylinder was made in sections 8 ft. long, with angle iron rings at 
either end for the purpose of joining them together with i in. bolts. Owing to 
the large number of cylinders, and their comparatively short distances from one 
another, it was deemed expedient, in view of the rough weather to be contended 
with, to erect a temporary timber staging for placing the cylinders, rather than 
employ any other method which might have presented various inconveniences in 
the transport of concrete and other material. On this timber staging, which, 
owing to the nature of the case, was in itself a work of some magnitude, six tim- 
ber guides, 15 in. by 12 in. by 14 ft. long, were securely placed at the exact site 
for each cylinder. It was also furnished with three lines of rails for 45 ton travel- 
ing cranes, and with four lines of metre gauge for trucks used in transport of 
concrete and in the removal of the excavated material, &c. The staging was 25 
ft. high above water level, and was made of piles 12 in. by 12 in. stiffened with 
diagonal bracing above and below water. 

The operation of sinking a cylinder was as follows: — Heavy temporary 
timbers having been placed on the lower part of the stage at about water level, 
forming a strong platform between the guides previously referred to, the bottom 
length of 15 ft. was brought from the shore by means of a traveling crane, and 
deposited on it. The inner and outer cylinders were then built up to a height of 
39 ft., and weighing altogether close on forty tons, were lifted by means of the 
traveler to a sufficient height to enable the timbers on which they rested to be 
withdrawn. The whole cylinder was then lowered into the sea until it floated by 
reason of the annular space between the inner and outer cylinders. A wrought 
iron cover was then placed over the inside cylinder, the joint being made air-tight 
by means of inch bolts and packing. On this cover two lengths of 3 ft. diameter 
shaft cylinders were bolted, and other lengths of these and of the outside cylinder 
v/ere added, till the whole rested on the bottom with the top of the cylinder rising 
above the upper stage. As the cylinder sank the annular space was filled in with 



I034 



USE. 



Portland cement concrete 3% to i up to the height of the cover, and the concrete 
continued above that in the same form by means of temporary curbing. It was 
mixed by hand on bankers designed for the purpose, and placed one on either 
side of the cylinder, the material being brought from the shore in small tip 
wagons. 

The C3''linder in this position was ready for the reception of the bell or 
pneumatic apparatus proper. From Fig. 438 it will be seen that it consisted of a 
wrought iron case with semi-circular ends made to fit on to the shaft cylinders, 




FIG. 438 — HUGHES AIR LOCK — VALPARAISO HARBOR. 



and was designed with a view of requiring no men under pressure except those 
actually engaged in excavation. The air locks were formed as follows : — The two 
D shaped cases were furnished with covers or flaps worked from the outside by 
means of a hand lever fixed on the bar forming the hinge, which passed out 
through a small stuffing-box, the joint between the cover and the top of the case 
being made air-tight by means of an india-rubber ring attached to the former. 
A similar ring was fastened underneath the bottom of the D-shaped case for the 
purpose of forming an air-tight joint with the bottom portion of the air lock or 
skip case. This was suspended by two chains of gauge links, one on either side, 



USE. 1035 

ig round chain sheaves, so that when both the D-shaped chambers 
were closed and the compressed air admitted, one skip case could be raised 
and the other lowered simultaneously by means of the winch worked on 
the outside, the main shaft of which passed from side to side of the air bell 
through stuffing-boxes and carried the driving sheaves on the inside. 
It was the top of either of the skip cases coming in contact alternately with 
the rubber ring on the bottom of the case which made the joint complete and 
allowed the air lock thus formed to be opened by letting the compressed air 
escape from the inside of it. The cocks for the inlet or outlet of compressed air 
to the air lock^ were i^ in. bore, and linked together so as to be worked by one 
lever, controlled on the outside by the man in charge. Smaller cocks, K-i". 
bore, were provided on the inside, to be used by the workmen coming in or out, 
so that they could control the rapidity of the change of pressure to suit them- 
^■■sselves. 

Ttie buckets or skips for hoisting the excavated material were made to fit 
closely the inside of the skip case, and a convenient method of attaching a chain 
for emptying them was arranged by means of a pipe passing through from side to 
side of the bucket close to the bottom. Through this pipe a short bar of iron was 
thrust as it was raised from the air lock by a steam crane. The iron bar projected 
sufficiently on either side to admit of the attachment of the tripping chain. 

-The air bell was furnished with a signal gong, pressure gauge, safety valve, 
and air supply connections, with check valve and stop cock, as an additional pre- 
caution to be used in the event of a breakage in the hose joining the iair supply 
pipe and the air bell. There was also a 3-in. cock in the cover of the 8-ft. cylinder 
for use in case of its being necessary to eject water from the cylinder otherwise 
than by forcing it through the bottom. Means were provided also for attaching 
a small flexible pipe for drawing off compressed air for working a pump to supply 
water for the concrete. The arrangement was completed with a small wire rope 
ladder hung from beside the air locks, and reaching nearly to the bottom of the 
cylinder, to enable the men to go up or down in case the machinery required ad- 
justment in any way. It was at first intended to work the hoisting and lowering 
by compressed air by fitting steam cylinders to the winch on the outside, but labor 
being cheap enough, it was not thought necessary. The compressed air was fur- 
nished by means of a stationary engine on shore, with two> air pumps, 15 in 
diameter, 2 ft. 8 in. stroke, surrounded by tanks of flowing water to keep them 
cool. It was led thence by iron pipes to within a few feet of the cylinders, the con- 
nection with them being made with a flexible hose, 3 in. internal diameter. As 
a rule, two foundations were sunk simultaneously. As the excavated material was 
removed from the bottom edge, the cylinders generally followed down by their 
own weight, but it was sometimes found necessary to let all the compressed air 
escape from the inside, and thus get rid of the buoyancy caused by the displace- 
ment of the water by the compressed air. 

The great increase of weight brought into play by this means generally re- 
sulted in the cylinder sinking rapidly to a depth of 5 ft., 6 ft., or more at a time, 
but there was always the risk of a considerable quantity of sand, etc., being forced 
in by the inrush of water from below. 



1036 USE. 

When the cylinders were sunk to the required depth — which in some cases 
amounted to 107 ft. below water— some 8 ft. or 10 ft. of concrete was put in 
carefully, and the air pressure maintained till it set. 

It was during the hardening of this concrete that the chief use was made of 
the safety valve which by maintaining the pressure at a certain point, obviated the 
possibility of compressed air blowing out at the bottom of the cylinder, and so 
causing unsound work or troublesome leaks in the concrete. 

The concrete put in under pressure was placed directly in the skip cases, 
which were tipped like buckets inside the cylinder, so that no buckets or skips 
were required. 

When it was sufficiently hardened, the pneumatic apparatus, including the 
cover of the 8 ft. cylinder, was removed, and the whole of the cylinder filled up 
with concrete 8 to i, cast in from above. Two men were employed under pressure 
at a time in each cylinder, working four hour shifts ; and in some cases the usual 
results of working under compressed air were noted, viz., bleeding at the nose and 
ears, headache, rheumatic pains, etc., but with one exception — there were no fatali • 
ties. In one case fatal results followed from the neglect of a workman to give 
the usual signal that it was a man and not material that was coming out. The 
consequence was that the pressure was released suddenly, and he found himself 
paralyzed from the waist downwards. He at once went again under pressure, 
and came out gradually; but the mischief was already done, and the attempted 
remedy was of no avail. He died in hospital some three months afterwards from 
the indirect effects of the paralysis. 

As a rule two cylinders were being sunk under pressure at the same time 
as two others were got ready for the operation. 



REGULATING TEMPERATURE OF BUILDINGS BY COMPRESSED 

AIR. 

We are enabled to present a plan showing in detail the system employed by 
the Davis & Roesch Co., of New York, for the regulation of temperature in build 
ings of all kinds. To control the temperature of rooms it is necessary to regulate 
the heat, and, wherever convenient, to also regulate the ventilation. The above 
system provides fully for both, and the results have proved to be very satisfactory. 
An installation similar to the one shown in the drawing has lately been made in 
the residence of Mayor Charles J. Fisk, of Plainfield, N. J. The temperature of 
the rooms is kept at the desired degree by the operation of thermostats, dis- 
tributed throughout the house, and compressed air is conducted through 1-16 inch 
tubes to the thermostats and to the flues which admit the hot air, completing a 
circuit that automatically opens and shuts the dampers in the flues and also the 
drafts of the furnace. 

The heating of the house mentioned is by the indirect hot water system, 
but any system of heating may be controlled in a similar manner. 

As operated in this instance the cold air enters from the outside and 
passes to a chamber, where the radiators are located, and the air is there heated 
and continues on to the rooms. 



r 



USE. 



1037 



The thermostats are placed in the rooms to be controlled, and connection is 
made between them and the dampers in the flues by the compressed air tubes. 

With the temperature at 50 degrees and the heat just beginning to radiate, 
the indicator of the thermostat is placed at the degree on the thermometer at 
which the temperature is desired. The temperature desired in the illustration is 
70 degrees Fahr, The heat coming into the room acts upon the thermostat, and 
when the temperature reaches 70 degrees the compressed air is turned on by the 
thermostat ; the diaphragm attachments controlling the dampers are fitted, and the 
heat is shut off. The moment the temperature falls below 70 degrees the com- 
pressed air is released and the dampers are opened. In this way a steady tempera- 




fiG. 439 — THERMOSTAT. 



ture is maintained, the system working constantly with variations within one 
degree of temperature. 

A small hydraulic air compressor, of novel design and automatically regu- 
lated, is placed in the cellar ; this supplies the air receiver, maintaining a constant 
air pressure of about teft pounds, although only about five pounds pressure is 
required to operate the system. 

F>?- 439 shows the internal mechanism of the thermostat. It is operated by 
the direct action of Compressed air, and although appearing of complex construc- 
tion is in reality very simple of action and requires but litle care. It is easy to 
adjust and controls the slightest variation in temperature. The action of the 
instrument is produced by the expansion or contraction of scientifically combined 
metals so sensitive as to respond even to the warmth of the human breath. 



I038 USE. 

In another installation which we have seen, the window and hall transoms 
of an office building are also connected with the system. The operation is as 
above described, opening the transoms and closing the valves of the steam radi- 
ators when the temperature has risen to the desired point, and closing the tran- 
soms and turning on the steam as soon as it begins to fall. 

The system can be applied to any number of rooms, and each room may be 
regulated at different degrees of temperature. 

The device insures the maintenance of a comfortable and healthy tempera- 
lure, and at the same time, by directly controlling the generation of the supply of 
heat, produces economy in the use of fuel, using it only as the requirements of the 
various rooms indicated by their several thermostats demand. 



SPREADER CAR, G. C. & S. F. RY. 

A line of improvement which seems to be meeting with considerable 
development in maintenance-of-way work this season is the designing of 
spreader cars for leveling down earth or ballast at the side of the track. The 
car is the creation of Mr. E. McCann, general foreman of bridges and build- 
ings of the Gulf, Colorado & Santa Fe R. R., where is has been put into service. 
The machine was built at the request of General Superintendent W. C. Nixon, 
who has kindly supplied us with data. 

The machine consists of spreader wings fitted to an ordinary fiatcar and 
provided with hoisting apparatus. The wings are of the ordinary heavy plank 
construction, faced with boiler plate and hinged to the car by means of heavy 
struts ironed off and well braced with angle irons. Each wing is divided into 
two sections, the rear section extending from the ends of the ties outward, and 
the forward section from the rail to the ends of the ties and overlapping the rear 
section. The intention of the forward section is, of course, to clear away 
material from the rail and uncover the ties, while the rear section cuts to a 
depth even with the bottom of the ties, or below if desired. The front section is 
hinged to a heavy bar extending diagonally across the corner of the car, and 
a piece of stout chain is attached to the rear section to take the longitudinal 
stress. The side pressure against the front section is received by a hinged strut, 
which abuts against a stop block bolted to the under side of the end sill of the 
car. The side thrust against the rear section of the wing is received by struts 
abutting against heavy timbers extending across the car, underneath the sills. 
There is a heavy timber box at either end of the car for ballast loading, to hold 
the car to the track. 

The apparatus for hoisting the wings consists of four 8-inch cylinders 
mounted upon the top of a framework which is sufficiently high to clear the 
wmgs in their raised position. These cylinders operate pistons which have a 
travel of about 5 feet, and the piston rods are fitted to a cross head, to which 
are attached two pulleys, around each of which is doubled a wire cable for hoist- 
mg the wmg on one side of the car. The pistons thus pull the end of the 
cable a distance equal to twice the travel of the piston. The wings are operated 



f 



USE. 1039 



by one man, who stands upon a platform suspended from the top of the frame 
and handles the air cocks of the cylinders. The air for operating the hoisting 
cylinders is taken from the brake system of the train, air storage being provided 
for by a reservoir located at one end of the car, on top of the ballast box. The 
cable for lifting the wing on each side is attached to the rear section, which also 
lifts the forward section, which comes to rest in a notch in the corner of one of 
the posts of the A-frame. In lifting the wings they are revolved past the center 
and thus rest in stable equilibrium. In lowering the wings to position they are 
shoved over the center by means of a lever and dropped to working position by 
gravity, being controlled in their fall by air in the cylinders. The wings can be 
put into working position within a minute from the time the car stops for that 
purpose, and in passing over bridges or cattle guards they can be raised to 
clear in a very few seconds, and let down again into working position without 
requiring the train to stop. As a precaution against any failure of the air supply 
a rope tackle is suspended from the framework for hoisting the wings in case of 
necessity. 

The machine was built to prepare banks to receive the ballast after having 
been widened out by material unloaded from trains. The machine has been in 
operation for about four months, during which time some minor improvements 
have been made, one of which consists of a roller on the forward sect^ n of 
the wing, to prevent the end of the wing from scraping against the rail and also 
to permit it to pass safely over rail braces and joint splices. In the use of ma- 
chine, dirt has been leveled down on the shoulders for a distance of a half mile 
in 13 minutes from the time the engine stopped to begin work until the machine 
was folded up to clear. The operation of the machine has been found to be so 
satisfactory that others will be built for the work of this company. The pres- 
ent machine was built in the company's shops at Cleburne, Tex. — Railway and 
Engineering Review. 



PNEUMATIC WORK.* 



I wish, before commencing the few remarks I have to make, to thank you 
for the honor you have conferred on me in asking me to speak on this subject. I 
wish to thank you before I begin, because your committeeman, Mr. John W. Neil, 
asked me how long I expected to speak. I told him I thought I could say all I 
have to say in a quarter of an hour. He smiled and said: "So long?" I will try 
and cut it shorter. 

In the first place, in regard to the pneumatic work foundation, to be done by 
the pneumatic method, your invitation committee asked me to read a paper on 
'"Pneumatic Foundations." In these days of bicycles we are all very familiar 
with the pneumatic tire ; some of us know the luxury of the pneumatic mattresss. 
We associate in our minds with anything "pneumatic" an idea of something 
springy ; that will bounce. I can assure you that is not the kind of a foundation 
Mr. Bouscaren wants for his pumping engine ; he does not want something that 
will jump up and down at every stroke of the pumps, but he wants something 



♦Address of Mr. D. E. Muran to the Central States Water Works Association. 



I040 USE. 

very solid. That is what we are trying to give him. The pneumatic method in 
general is simply a way of doing what under different conditions could be done 
without the pneumatic method. We simply employ it to keep out the water. It 
has been a growth, a gradual development from the old diving-bell. It is not 
necessary for me to tell you what a diving-bell is, as you are familiar with its 
principle, and know that it is shaped something like a goblet turned upside down, 
and allowed to settle in the water; as it settles, its weight keeping it steady and 
the sides at the same level, the air caught and imprisoned in the diving-bell is 
compressed ; the more the contained air is compressed, and the less becomes the 
air content and the greater the content of water. That was used in the last cen- 
tury by some ingenious man, first as an experiment, then afterward In recovering 
treasure from sunken wrecks. It had a limited use in that way. It was not until 
the development of the machinery end of the business that somebody put com- 
pressed air into it, and it became of value to the engineer. The diving-bell in its 
simplest form had a certain amount of water in it; that water prevented work 
being done right at the bottom of the well. (The speaker drew a rough sketch on 
the blackboard to illustrate the principle stated.) Where the diving-bell rested it 
was necessary for men to work in a certain depth of water which rose in the bell. 
Now, by the introduction of compressed air, the pressure in the air space could be 
made to equal the water pressure below ; the result would be that the water would 
be prevented from thus rising in the bell as it did before the use of the compressed 
air; and the workmen thus could stand on the bottom, where the bell rested, 
dry-shod. 

The development from that to the modern caisson was a gradual growth, as 
I have said. 

One of the earliest instances in which the pneumatic method was used in 
the building of a pier was the Salt Ash Bridge, built by Brunei. I have not my 
books of reference here, or I might have looked this up ; but it is unimportant. It 
was a crude method, extremely clumsy and difficult. There was a wooden foun- 
dation for the pier cut up into innumerable small pockets, with tortuous narrow 
passage for egress. The work was done under great difficulties ; the workmen had 
to* go up in these narrow chambers in the caisson, fill bags with mud, and then 
carry them to the air-lock ; and in that way the excavation was made. It was 
very slow and very difficult. The development from that day to this has been a 
development in the direction of the perfecting of the caisson as an excavating ma- 
chine. The caisson has now become like a box turned upside down; and the 
larger the opening inside, and the easier the means of getting material out, the 
easier the caisson for working in it. As the structure requires considerable 
strength in all its parts, the calculation of a caisson is a matter of great difficulty, 
because the strain that comes upon it is not a definite one, as in bridge structures, 
where you can separate the strains and deal with them as you please. In a caisson 
there is no telling what strains will come upon it. The real pressure is a problem 
that defies accurate calculation. There is no assumption upon which it can be ex- 
actly calculated. It must be gotten at as the result of experience guided by engi- 
neering knowledge. 

From the primitive diving-bell, which had no method of ingress or egress, 
except under the edge, the modern caisson has developed and become a structure 



I 



USE. 



104 1 



in its simple form like a rectangular pier, thus: (making sketch on blackboard). 
.Openings are carried up through the pier, or whatever the structure is, through 
the caisson and through the masonry on top. There are several ways of making 
the excavation. It is necessary to get dirt out from below the pier in order to 
sink the caisson. The first, and perhaps the simplest method, which you will 
probably see at California this afternoon, is by blowing it out. The air pressure in 
the caisson being in general slightly higher than the water pressure, this air pres- 
sure has been found sufficient to carry a certain amount of material with it 
through the pipe. It is usual to put in a 4-inch ordinary iron pipe, having at the 
top an elbow generally of a large radius. This pipe is carried through the caisson 
in an air-tight manner. The lower end has a plug valve giving a full 4-inch circu- 
lar opening; and below the valve an extension of the pipe and usually another 
elbow. Sand or other fine material, as the air escapes, is fed by hand or shovels 
-in front of the pipe; and the current of air going through the pipe carries with it 
a very large proportion of this soft material. That method is very simple, very 
rapid, very safe; but it does not work with rock. It works with difficulty with 
certain kinds of clay. Certain kinds of clay we cut up with a jet of water and 
carry it through the pipe. That led to the introduction of an excavating air-lock. 
I want to say a word about air-locks. An air-lock is an arrangement for 
getting from the inner pressure to the outside pressure. In its simplest form it 
consists of a cylinder, or boiler, with two heads. On the upper head there is a 
door, and the lower head also has a door. One of these doors is always kept 
closed to retain the pressure. Both doors open downwards. At its lower end 
there is a shaft or pipe connecting it with the caisson ; men or material can come 
up this shaft and go through this lower door, and while it is opened the upper 
door is closed. At this time the pressure in the air-lock will be the same as the 
pressure in the caisson. The lower door is then closed, shutting off the supply 
of 'ir from the caisson into the lock; the valve at the upper door is then opened, 
allowing the compressed air contained in the lock to escape ; and when the air 
in the lock is the same as the outside pressure, the upper door will drop, and com- 
munication is opened with the outside air. In the same way, returning, the lower 
door being closed, the men may go through the upper door, which will then be 
closed and the lower valve opened, allowing the air in the caisson to flow in the 
air-lock till the pressure there is equal to the pressure in the caisson, when the 
lower door is dropped, and then communication is open to the caisson. This lock 
can be used in excavation by having the workmen carry up through it bags of 
broken rock, or other material. That was improved upon later on by the so-called 
"O'Connor bucket." The bucket carried a valve on the top of the bale, which 
closed the hoist-pipe. In this arrangement the hoist-pipe, or shaft, passed 
through the roof of the caisson, and terminated at its lower end in a cylindrical 
extension projecting into the working chamber below the roof of the caisson. 
Just below the roof of the caisson the shaft contracted slightly, and was fitted 
with a conical valve seat corresponding to a valve-plate of circular form fastened 
to the bale of the excavating bucket. When the excavating bucket was lowered 
through the shaft into position in this cylindrical extension in the wooden cham- 
ber, the valve on the bale fitted into the conical valve seat, and was held there by 
means of set screws, operated from the interior of the working chamber. Doors 



T042 USE. 

in the side of this cylindrical extension were then opened, allowing dirt and small 
pieces of rock to be shoveled into the bucket. When the bucket was filled, 
these doors were closed, the pressure equalized, and the the conical valve released, 
when the bucket and its contents could be hoisted to the surface, dumped, and 
returned for another load. 

An improvement on this method was a pneumatic hoist devised by the emi- 
nent bridge engineer, Mr. Geo. S. Morison. I have never seen this method in 
operation, but understand that it is satisfactory and efficient. It goes among the 
"sand-hogs" by the euphonious name of "Morrison's go-devil." 

I am using at California a lock which enables an ordinary bucket, or even a 
barrel of cement, to be passed in and out of the caisson without detaching it from 
the hoisting rope leading to the derrick. The lock has a simple lower door hinged 
on a shaft, which shaft extends to the outside of the lock through a stuffing-box. 
On the outside is a counter-weight lever and counter-weight, to balance the door 
and afford means of operating from the outside. Above the lower door is a cylin- 
drical section, called the bucket chamber, large enough to contain the bucket. 
The opening above the bucket chamber, instead of being closed by a single door, 
is closed by two doors working to and from the center. When these doors are 
closed they completely close the opening, and form a tight joint with each other, 
with the exception of a small opening at the center. In this small opening at 
the center fits a stuffing-box of simple design, through which the hoist-rope 
passes. The two doors then close around the rope contained in the stuffing-box 
and completely prevent the escape of air through the opening, while permitting 
the rope to pass freely. As soon as the bucket is filled in the working chamber 
an electric bell rings above, and the engineer at the derrick hoists the bucket into 
the bucket chamber. The lower door is than closed, a valve is opened permitting 
the air in the lock to escape, the upper doors are then opened, and the bucket is 
hoisted out, the stuffing-box remaining on the rope just above the bucket. In 
returning, the operations are reversed. 

The caisson is an excavating machine, as well as a foundation, and must be 
considered in that light. Its development has been largely due to the specialists 
who have been employed in this line of work. Just as in the bridge shops in 
America the design has been developed, so in caisson work men like Eades, 
Sooysmith, Morrison, Hermany, and others have added from time to time new 
points, all tending to make the caisson more and more efficient in its dual capacity 
of an excavating machine and foundation. 

Before I leave the subject of the development of the caisson, I must say a 
word for "the man behind the gun"— the "sand-hog." He is a tramp ; he has no 
home, no family, no morals, no religion ; he is nothing but a "sand-hog." He got 
the name from the fact that at one of those jobs at Havre de Grace, close to the 
Chesapeake Bay, the farmers' hogs used to go down at low tide and root in the 
sand ; they covered themselves with mud ; and the workers in the caisson, seeing 
the close resemblance between themselves and the farmers' hogs rooting in the 
mud, christened themselves "sand-hogs ;" and ever since then they have gone by 
that name. They are a class by themselves, and follow a pressure job from one 
part of the country to the other. About the time we are ready to put on the air, 
some seedy individual pokes in his head at the window and says: "Say, Mr. 



USE. 1043 

Moran, when are you going to put on the air?" Yet the sand-hog has done much 
to develop pneumatic work. It was a "sand-hog" who first suggested the idea, 
or observed the fact, that by allowing a slight flow of air above the blow-pipe 
soft material could be better and more easily blown out ; and so, without remem- 
bering the name of the "sand-hog" who suggested the plan, we arrange to have a 
little vent in our blow-pipe. 

The "sand-hog" is an interesting study to me; he has his peculiar disease, 
the "caisson disease," called by the "sand-hog" the "bends." The action of high- 
pressure compressed air on an ordinary man is temporary; you feel it while you 
are in it; an hour after you are out you don't feel it, and you are all right. But 
it may make great havoc with the human system. It affects the ears. If the 
Eustachian tube is clogged, the pressure on the outside will rupture the ear drum. 
I know engineers and "sand-hogs" who are deaf from that cause. It also will 
produce paralysis, temporary or permanent; and it may produce death. The 
subject has been studied both from a medical and practical standpoint. I am 
glad to say that in recent years the mortality and injury from the use of com- 
pressed air is greatly reduced. Still, there is always present danger in compressed 
air work. The "sand-hog" knows nothing about the "caisson disease," technically 
so-called. He only knows it as "the bends" from practical experience. It was 
many years before I found out how this disease got the name of "the bends." It 
seems that when Eades was putting down the foundation of the St. Louis bridge, 
there was a peculiar form of style of carriage among fashionable ladies of this 
land, which was known, and is, no doubt, remembered by many of you, as it is by 
myself, as "the Grecian bend." And when a workman came out of the caisson 
and felt pains in his knees, and a "crick" in his back, and when he could not walk 
easily or well, his friends would laugh at him and say : "You are trying to walk 
the Grecian bend." In time the "Grecian" was dropped, and the disease was 
r.amed by the workmen "the bends." I don't think our workmen here on this job 
will be so troubled, because the air pressure is very light. We can do much to 
relieve them now-a-days if they do get "the bends." 

Now, gentlemen, this is a windy subject. We have to keep our compressors 
running day and night; and sometimes I think when I get started on this subject 
I also will run on all day and night ; but I will not do it ! I am at the end of my 
fifteen minutes and will close, thanking you for your kind attention. 

A hearty vote of thanks was tendered to Mr. Moran at the end of his 
remarks. 



SURFACING RAILROAD TRACK BY MEANS OF COMPRESSER AIR. 

We present two views of the method of surfacing railroad track by means 
of compressed air ; one, a shop view of the mechanism in its present development, 
the other, a view taken while in operation in broken stone, in maintenance, the 
most difficult and expensive of all ballast. 

The theory underlying the method pursued since the birth of the railroad 
has been, that material be driven by blows under the ties to resist the vertical 
gravity of trains, but in practice no two men thus tamp equally, the train develops 



I044 



USE. 



the weak or unequal points, and each recurrent tamping to correct the inequalities 
largely destroys the work previously done. 

In the compressed air method, the theory and practice is reversed. 

The inevitable train gravity is availed of and relied upon to consolidate the 
foundation to its full possibility, and the cavities beneath the ties disclosed by rais- 
ing the track to the desired surface are then filled from the ends of the ties with 




FIG. 440 — MACHINE FOR SURFACING RAILROAD TRACK BY MEANS OF COMPRESSED AIR. 



suitable material conveyed by the air blast without other disturbance of the com- 
pacted roadbed. 

In renewing ties (50,000,000 per year are required in this country alone), the 
same theory is followed. 

The spikes of the new tie are not driven home, but the tie is held up to the 
rail and thoroughly filled with suitable material from its open side, the ballast 
other than at the ends is then replaced and dressed, and the tie gets its first tamp- 
ing by train gravity, "shimming" it if necessary until the bed has reached its 
greatest compactness, and then home spiking it and filling the vacant space as 
before described. 

The method finds immediate favor with trackmen, as, while each man is 
obliged to steadily perform his part in the operation, lest the work of all stop, 
the manual exertion required of each is very much less than in the old method. 



USE. 



1045 



The material found in use to be the most satisfactory is clean gravel, fur- 
nace slag and stone screenings, reduced to a size not too large to enter the cavities 
under the ties. 

The advocates of the process claim for it: 

The advantage of using under the tie, a material suitable as to size and 




FIG. 441 — SURFACING RAILROAD TRACK BY MEANS OF COMPRESSED AIR. 

substance, without regard to the oft-times inferior quality of the ballast in the 
roadbed. 

Evenness of its work. 

Readiness of its operation in slight elevations, down to ^ inch. 

Greater accomplishment per linear foot of traclc, per man per hour. 

Greater serviceability of the tie in coarse ballasts, owing to limited area of 
bearing points, and to base destruction by present tamping practice. 

Practicability for use in metal tie track, hitherto not surfaceable. 

The conserving of the time and labor previously bestowed upon the work. 



BALLAST INJECTOR. 

A compressed air apparatus for placing ballast under depressed railroad 
Lies has been invented. It consists of a small Root Blower run by hand, and a 



1046 USE. 

double-tubed injector. The blower is clamped upon a rail for support. It sup- 
plies air through a flexible hose to the injector, which has a hopper at the top. 
Suitable ballasting material is fed to the hopper. Air is allowed to flow through 
the air supply pipe, and the ballast is drawn from the hopper. Air and ballast 
meet at the bottom of the tubes. The air carries the ballast under the tie from 
one end nearly to the other. It operates with great nicety, and has been experi- 
mentally tried on several roads. It does not displace the ballast at the sides of 
the tie. No tamping by hand is necessary. The inventor claims great saving 
in cost in ballast, heretofore requiring expensive work in surfacing. 



RECENT EXPERIMENTS IN TAMPING TRACK BY COMPRESSED 

AIR.* 

In this country the engine has grown into a practically perfect mechanism, 
and the station and the coach to the convenience and comfort of a hotel. Besse- 
mer's invention and the application to it of modern machinery of tremendous 
power, has made it possible to double the weight of the rail section withoivt 
increase in its cost, though we now, seeking a low first cost, wrongfully merely 
squeeze the metal into the prescribed section, instead of as in earlier days, rolling 
it to a finish. And the joint problem, to the solution of which the inventive genius 
of the world has devoted itself for years, is still with us unsolved. 

In one very material feature of railroad physics, of which I wish more par- 
ticularly to speak, we have made no advance. As George Stephenson surfaced his 
track, so do we to-day, theoretically and practically, seeking to overcome the 
inequalities caused by train gravity in the foundation of our ties, by pounding 
more material under them in resistance to that gravity. We realize its general 
ineffectiveness, but few seem to appreciate its importance as an item in the general 
operating expense account. 

Mr. Tratman, in his latest work (Railway Track and Track Work, 1897), 
has evidently made a strenuous effort in this direction. For the railways of this 
country alone, he gives for 1895, out of a total expenditure for operating expense 
of seven hundred and twenty-five millions, the cost of the work of one hundred 
and eighty-five thousand foremen and sectionmen, as sixty-nine millions, exclud- 
ing rail and tie renewals, renewals and repairs of culverts, bridges, fences, build 
ings, and kindred structures, but he also evidently fails in finding the record of 
cost of this item. 

We can try to arrive at it approximately from other sources. 

Nearly all roadmasters and foremen fix the proportion of their pay roll ex- 
pended on tamping as at least 50 per cent. 

One hundred and eighty-five thousand foremen and section men, make an 
average of a little more than one man per mile, and their average pay is annually 
nearly or quite four hundred dollars — or by this estimate for this item, two hun- 
dred dollars per mile, nearly four cents per linear track foot. 

* Paper by Mr. F. R. Coates, Roadmaster N. Y. Div. N. Y., N. H. & H. R. R., read before the 
Annual Convention of the New England Roadmasters' Association, Revere House, Boston, 
August 17, 1898. 



USE. 1047 



^ft In the most expansive tamping, and the most severe upon the men — coarse 
^ffoken stone — foremen who have recently been asked to answer the question 
' say that in this work, done as well as it can be done, and as it should, of course, 
be done, one and one-half feet per hour is the expectancy of performance, equal to 
a cost of eight and one-third to ten cents per track foot. Actual timing has veri- 
fied this, and it has been sustained by the opinion of higher officials in mainte- 
nance of way departments, though they assert that this work requires no repetition 
for a year or more. 

In sand or gravelly loam ballast, where the tamping bar is useless, where 
shovel tamping is practiced and the best work not expected, nor obtainable, no 
figures as to cost are available. It is probably much less than the average given 
above of two himdred dollars per mile, and a total of thirty-seven million dollars 
per annum, but probability is increased, in our belief, in the very much higher 
average on roads that expect the best results and strive to attain them. 

There ought to be a better way to do this work — cheaper, easier for the 
men, and more even and permanent in its results. 

In track surfacing we now expend an undetermined amount of time and 
money in tearing out the settled ballast until we expose the lower face of the 
depressed ties, and then raising them to the required level we drive material under 
them for a new foundation, and necessarily in doing so, disturb or destroy the old 
foundation. Then we refill and redress the ballast, and leave the track in the hope 
that the new foundation will prove as good as the old one made by train gravity, 
for the locomotive is the final tamper, its twenty tons weight on each tie finds all 
the inequalities of men's tamping, and will compact each tie's foundation until 
full resistance is met, without consideration for the work done by the men. 

We all recognize this, and none will question that train gravity is the inevit- 
able final tamping agent, and the best one, if it can be availed of and relied upon 
to do the work, and this is a question of creating the conditions necessary to its 
utilization. 

Theoretically, it would appear that if depressed ties or tracks were raised 
to the desired level, first removing only the ballast at the ends of the ties, there 
would be exposed the cavities beneath the ties requiring filling, their base and 
walls already compacted to the susceptible limit of the material, be that material 
what it may, from broken stones, the best, down to "gumbo," the very worst. In 
compacting this foundation, train gravity and the elements have done all that the> 
are capable of, and have done it better than is possible by any other means. 

Thus far there has been but little departure from our usual custom, ex- 
cepting that we have at the same moment raised and held both sides of the track, 
and under any method of tamping there is no doubt that this should always be 
done when needed. 

If now these exposed cavities can be filled with a suitable material, we 
should expect that trains, having previously exhausted their power in compacting 
the foundation, could now only exert it on the new material just filled in between 
the tie and the old foundation and would be confined to the compressing of that 
material, thus conserving and availing ourselves of all the time and labor previ- 
ously expended on the old foundation, which now we find ready for us, and thor- 
oughly compacted. 

The theory is indisputable ; the problem is to complete the process. 



to48 USE. 

We will now consider the duties that ballast is called upon to perforfti, and 
find that they are fourfold. 

First — It must be capable of draining the track. 

Second — It supports the ties and thus holds the track to surface. 

Third — It assists in preventing the track from creeping. 

Fourth — It retains the line. 

The question which now presents itself is how to surface the track with the 
least injury to the ballast and the bed it has made. From the foregoing it is evi- 
dent that the only method is by working from the ends of the ties. 

In England, on some of the roads, in order not to break up the foundation, 
the tie is lifted and gravel sprinkled under it from a small shovel shaped about 
like our tamping bar, the spade being a little larger. But the objection to this is, 
that though the train does the tamping, the side walls are broken down. 

The most promising effort in this direction has been in experimental work 
during the past five years in the use of the air blast. 

Its possibility once determined, the mechanical means were to be devised. 

The conditions were: 

First — Ready portability. 

Second — Determination of the necessary proportions between appliances 
and work to be done. 

Third — Adaptability to the use of all kinds of material and all conditions of 
surfacing work. 

These requirements have, with few exceptions, been fairly met, though 
mechanical improvements will, with more extensive use, undoubtedly suggest 
themselves in the future as in the past. 

The Root blacksmith's blower has thus far been found best adapted for 
conversion to this use. The mechanism is used by the ordinary track gang of four 
m^en, one or two of them being required to furnish the power, and all engaging in 
clearing the tie ends during intervals of train waiting. Where the work is of 
sufficient magnitude, a double gang uses one machine on each rail, materially 
adding to the rate of progress of each. The on-looker is at once impressed with 
one fact — there is no possibility of "soldiering" by any one man; each man fills 
his place, and the pause of one stops the work of all. 

The mechanism having demonstrated its practicability, a serious problem is 
is to develop the most economical method of placing suitable material convenient 
for use. In the ordinary picking up of low joints and loose ties in gravel road 
beds, the hand screens for excluding the particles too large to pass through the 
injector or to enter the cavity beneath the tie, seem to amply meet the require- 
ment, and equally so where fresh material has been brought for more thorough 
v/ork. Where the best of all ballast, stone, is available, the screening of the 
material to a size that can be used in the average cavity, say through a three- 
quarter inch screen, can readily be done at the breaker, and should be done without 
additional charge. If for use in coarse broken stone ballast, it has been found 
Ijest to screen out the particles below one-fourth inch in a first filling, as a large 
part of the screenings under this size wastes among the interstices of the ballast. 
The dust is everywhere objectionable and breakers should not load it for track 
use. 



USE. 1049 



^m The author of this paper is of the opinion that small stone is much more 
^Stable for tamping than large, using it from three-fourths of an inch to one 
and one-half inches. 

"In order to get a comparative estimate of the velocity with which water 
would drain through these different sizes, under similar conditions, the same 
bucket was used and four five-eighths inch holes bored in the bottom, ninety de- 
grees apart. By pouring in the same amount in each case, which was six quarts, 
with the coarser stone it passed through in twenty seconds, with the next size in 
Iwenty-two seconds, and with the smallest in twenty-four seconds. A larger stone 
is not so good for tamping as one of such size as will pass through a one and one- 
half inch ring. At times the roadbed will get into such condition as to retain 
water, and in this event the smaller the stone the more solid will be the foundation 
and the less the amount of water it will hold. 

"In view of these facts, it is conclusively proven that a small stone is much 
more preferable for ballast than a large one. And, further, if the specifications 
require the size of ballast to be such as will pass through a one and one-half inch 
ring, the large stones which meet the requirements in two dimensions, but are 
large in the third, will be kept out." 

In other kinds of roadbeds, a clean ballast, free from earthy matter, ought 
to be used, and the amount required for this purpose is small in comparison with 
the amount required for full ballasting. 

The mechanism in its present development is entirely a "surfacing," not a 
"track raising device," and the range of its applicability would seem to be from 
one-fourth inch up to one and one-half inch and the size of the material up to 
three-fourths inch. 

Material passed through a three-fourths inch round screen can be used, 
but its flow is much slower than the smaller sizes, as also is the speed of its 
projections. This can be readily realized when we know that a fair speed of the 
compressor shows but eight-tenths inch mercury pressure for the air which is 
conveying the material beneath the ties. 

I have seen the performance of another application of the air blast to this 
use, which, dispensing with all the mechanism, gives greater projectile force, but I 
am requested not to speak of it in detail until its adaptability is better developed 
and determined. Where the power is available it increases the accomplishment of 
each man among the trackmen by the proportion of them now used in furnishing 
power on hand compressors. I am told also that the electrical experts are clear 
in their opinion that where the electrical current is available, a portable motor will 
furnish all the power needed; thus, while retaining the compressor, also corre- 
spondingly increasing each man's performance on the track. 

In the experiments made at Stamford, Conn., on the N. Y., N. H. & H. 
Railroad, two adjacent pieces of track, each fourteen rail lengths, were taken, 
they being under the same conditions of traffic. One was surfaced by men on a 
spurt and the other by the machine. The former attained a speed of five feet per 
man per hour, and the latter eight and two-tenths feet. In this, however, no 
allowance was made for screening the material, which would in all probability 
reduce the speed to eight feet per hour. In one year it required the expenditure 
of thirty-six hours of one man's time to maintain the surface of the portion put 
up by hand, and of two hours for that which had been surfaced bv the machine. 



I050 USE. 

Our present method is largely a matter of "strength and stupidity." The 
method under consideration is machinery action and its best service must be the 
outcome of practice, for there are conditions, which we have not been forced to 
notice in our present practice, which must be met, when learned, in the new. 

For instance, in using gravel ballast, it is difficult to secure even work 
where squared and hewn ties are indiscriminately used. The cavity under the 
square tie is a perfect box, but the base of the hewn tie when raised from its bed 
leaves two vertical conical spaces above, too small to be reached and filled, but the 
restlessness of water-worn material — gravel — is excited by train pressure and the 
pebbles "churn" until the sandy portion has been forced upward, into every 
crevice. The remedy is to use the bar in downward tamping of the edges of the ! 
hewn ties, so as to close these small spaces at the side of the tie before the passage 
of a train, and it would seem advisable in using this method, in gravel or similar 
roadbeds, when the best work is desired, to always vertically tamp hewn ties. 

In the application of the one use of air above referred to, the condition of 
the material seems to be of little importance, though the flow of dry material is, of 
course, the most rapid. In the use under consideration — the hand compressor — 
creating a back pressure in the descending ballast tube, bituminous cinder, because 
of its light gravity, is worked with difficulty; not a serious objection to those who 
believe it unfitted for tamping material in main track. 

In using the hand compressor, the dryness of the material naturally con- 
tributes largely to the rapidity of its delivery. 

Lengthened tie service is claimed for it, notably in coarse stone ballast, 
where many permit the bad practice of tamping the track up to grade instead of 
otherwise lifting it, frequent tamping resulting in champing off the tie base until 
the tie section assumes the shape of the letter U. Users of the air method find 
the splinters thus driven into the cavity a serious obstruction. 

The method is believed to have solved the hitherto unsolved problem of the 
Tcvmping of the interior of the steel tie. This, though of great importance upon the 
.35,000 miles of metal ties in Europe, requires no consideration from us at present. 

As the cost of our present method is, so far as I know, practically unknown, 
it is too early to discuss the economy of the new method. Permanency of the 
work of the respective methods is a feature equally important with the first cost 
Comparative tests for at least one year would seem to be necessary to determine 
these two points, though, I am reliably informed that in gravel roadbeds the speed 
obtained was far in excess of that procurable with bars and the work required 
no repetition until the relaying of the track three years subsequently. 



THE "BELLY POUNDER. 



A nery novel application of the Steam Rock Drill is shown in the illustration 
on our cover, and in this form is known among the packing houses as a "Belly 
Pounder," or, to speak more plainly, it is used in taking the "kinks" out of the 
hog bellies and straightening them out, as they come to the machine in a frozen 



USE. 



105 1 



state, afterwards being cured and packed in boxes for shipment. The machine 
shown in the photograph is a modification of the Rock Drill, with the rotating 
mechanism replaced by a straight guide, forcing the piston to strike a direct, 
straight blow without rotating. The piston has a specially forged head, to which 
is bolted a wooden block, or paddle, about 8" x 14" and 2" in thickness. Instead 




FIG. 442 — BELLY POUNDER. 



of the usual form of crank on the feed screw, it is replaced by a pair of bevel gears 
and extension crank, locating the handle convenient to the operator standing on 
the floor. This permits of the raising or lowering of the machine to accommodate 
varying thickness of meat. The mounting shown is the regular double screw 
column, such as is used for mounting the drill in tunnel work, the drill being at- 
tached to the arm in the same manner. The cylinder of the machine is 2}i" in 
diameter, and it can be operated with compressed air as well as steam. 



I052 USE. 

This "Pounder" is now being used by quite a number of the large packers, 
several of the machines being in operation at the Union Stock Yards, Chicago. 
The illustration shown was made from a photograph taken at the works of The 
International Packing Company, Chicago. The saving effected by their use will 
be appreciated when it is stated that with one of these machines a packer is able 
to take care of 400 hogs per hour, or to pound 800 bellies in that time. The users 
report that the work is much better done, requiring less trimming and waste. 
This, with only two men necessary to the operation of the machine, where they 
formerly employed six men with paddles to accomplish the same amount of work 
by hand; a saving in labor of four men. This item alone would in a short time 
more than pay for the cost of the machine. 



PNEUMATIC ELEVATOR DOOR MECHANISM. 

In these days of sky scraper office buildings the elevator is looked upon as 
the soul of the building, and it is the elevator service that rents the offices more 
than any other detail. A good deal of thought and studying is done to increase 
the efficiency of the elevator service. You may run high-speed elevators, but you 
cannot make your passengers run on and off the elevator, and that is where the 
time is lost. The elevator runner has to open the door to let his passengers out, 
and then close it, and in a great many cases much haste means less speed, as he 
has to stop the car and return to close the door. 

The Burdett-Rowntree Manufacturing Co., of 76-82 W. Jackson Street, 
Chicago, and of 120 Liberty Street, New York City, are the inventors and paten- 
tees of pneumatic elevator door mechanism, which causes the door to open by 
the time the car is level with the floor, and when the car is ready to leave the 
floor the man releases the foot button and goes on, knowing that if the door op- 
ened it will have to close. The mechanism is simplicity itself, consisting of a cyl- 
inder, piston, piston rod, and the admission of air is controlled by a pivoted D 
slide valve, opened by a tripping device on the car, and closed by a spring which 
throws the valve the other way. The door is entirely controlled by the operator, 
within a range of 20 inches, 10 on each side of floor. There is a small bar which 
interlocks with the valve trip and locks the door, preventing it from being opened 
from the outside ; also, in the '98 machines, the full pressure of air is on the rear 
end of piston at all times except when opening, and there being no dead centers 
the door has to keep closed. The doors are practically noiseless, being cushioned 
on a dash pot of oil, both opening and closing. This d<Des away with all adjust- 
ment of the valves, there being only one small admission cock, which regulates 
the amount of air needed. The air is supplied from a pipe which runs the full 
length of the elevator well, tapping it for the machines at each floor. In the base- 
ment is placed an automatic air pump, receiver, and a reducing valve, which re- 
duces the air to 15 pounds, that being the pressure used by the machines. The 
gain in service is very material. In the Surety Building in New York City they 
claim a saving of 20 seconds per round trip of elevator, and in the course of a day 
this would add into time very materially. In the Stephen Girard Building, Phila- 



USE. 



1053 



delphia, a 13-story building, are four elevators, which carry 4,000 people per day, 
Mr. Dinsmore, Engineer for the Girard Estate, told the writer that they could 
not begin to handle their traffic without the door mechanism. The largest instal- 
lation, consisting of 216 doors, is in the Empire Building, New York City. There 
are 180 single, 26 double, and ten folding gates within the cars. These machines 
are of the latest designs and with all the changes found necessary since the first 
plant was installed three years ago. There are now 41 office buildings equipped 
with these gates, and there are a large number of orders for projected buildings. 
They have been found to be of the greatest utility in department stores, where 
their traffic consists of women and children, who are naturally slow and timid in 
entering and leaving the elevator, and where it is necessary for the operator to 
have his eye on the passengers and his hand ready to assist them, his foot oper- 




FIG. 443 — ELEVATOR DOOR MECHANISM. 

ating the door. In B. Altman & Co.'s dry goods store they have double doors 
opening to the full width of the car operated by the mechanism. Also Marshall 
Field of Chicago, and R. H. White's department store of Boston, are now equip- 
ping their elevator doors whh these devices. 



PNEUMATIC GUN IN WARFARE. 

Interest in dynamite guns has been stimulated by the practical tests given 
to them in action during the late war with Spain, in Cuba. The Sims-Dudley 
field gun being at the front, proved to be very efficient, and demonstrated that in 
the hands of intelligent artillerymen this gun is successful. In the fight of the 
"Rough Riders" before Santiago Sergeant H. A. Borrowe had charge of the gun. 
He reported that the gun had been in action three times, and in all 20 shots had 
been fired with great effect. Other regiments were supplied with these guns and 
did excellent service. The testimony of officers and correspondents is to the 
effect that these guns have a fine moral effect, as well as being very destructive. 
This gun is popularly called a "dynamite gun," although any desired form of 
explosive may be used. It usually throws a projectile charged with Nobel's gela- 
tine, which can be handled, stored and used with greater safety than any other 
nitroglycerine explosive, and still produces in its explosion a more destructive 
effect than that of any other explosive. It is impossible to throw such material 
by the direct fire of powder, as the concussion would without doubt explode the 



T054 USE. 

charge. Therefore, the power used in the ejection of the projectile is compressed 

air, generated by a small charge of smokeless powder. The volume of gas pro- 
duced by combustion of the powder compresses the air contained in the tubes of 
the gun, and this air acts as a yielding cushion between the powder and the pro- 
jectile, and as the transmitter of the force from the one to the other. The eject- 
ing force thus acts upon the projectile with a prolonged and gradually increasing 
effect, instead of with the sharpness and suddeness of direct powder explosion. 

The bore of the gun is 2^ inches and the length of the projectile 
tube is about 14 feet. This tube is of a special composition, having a tensile 
strength of 80,000 pounds to the square inch. The barrel is not rifled, the rotation 
of the projectile being accomplished after leaving the gun by the action of the air 
upon the inclined wings on the spindle. The total length of the projectile is 36 
inches and it weighs when loaded 11^ pounds. It carries four pounds of Nobel's 
gelatine, which is equal in destructive power to at least 80 pounds of ordinary 
powder, and a Merriam fuse provides for the explosion upon impact or decided 
retardation, as by water, or the explosion may be arranged to occur at a prede- 
termined interval subsequently. 

Below the projectile tube is the combustion and compression chamber, 
which is a 4^ -inch steel tube 7 feet long. The firing is by an ordinary cartridge 
shell, containing seven or eight ounces of smokeless powder. This cartridge is 
placed in a small central tube, which projects only a short distance forward into 
the combustion chamber. The breech mechanisms are both thrown open by a 
single motion, the projectile and the cartridge are inserted at once, the breech 
mechanisms are closed by a single movement, and the gun is ready to fire. The 
firing is done by pulling a lanyard in the usual manner. Absolute certainty of 
operation is assured by the details and arrangement of the mechanism. There is 
no possibility of any discharge of the gun until both the projectile and the cart- 
ridge are in their correct positions and everything is ready to fire. In these par- 
ticulars, Mr. Sims, the inventor of the well-known dirigible torpedo, has contrib- 
uted much to perfect the original invention of Mr. Dudley. 

When the cartridge is fired the charge is driven forward in the large tube, 
while all the contained air is driven backward and through a large connecting 
passage into the projectile tube, so that practically all the air contained in both 
tubes is between the projectile and the hot gases. The action of the explosion 
upon this large body of air also insures a gradual instead of a sudden application 
of the pressure upon the projectile. The pressure is, however, applied so effect- 
ively that the range of this gun is from one and one-half to two miles, with a still 
greater range for those of larger caliber. 

The gun weighs 1,044 pounds. It can be quickly taken apart for 
transportation on mule back, or in difficult places all the parts can be carried 
by men. The parts can be assembled and the gun made ready for action in ten 
minutes. The cost of each discharge of this gun is but $35, while the guns using 
powder alone, with which it would be fair to compare it, weigh many tons and 
cost hundreds of dollars for each discharge. The zone of destruction caused by 
the explosion of the projectile is nearly 100 feet, and where its fire is directed at 
masses of troops the shock is so frightful that many besides the killed and the 
actually wounded are thrown out of the fight. 



USE. 1055 

The gun may be fired at almost any desired elevation or depression, so as to 
be available for attaching an elevated position or in firing at an object directly be- 
low the gun. The recoil of the gun is inconsiderable, and little noise is produced, 
so that it is difficult to locate the gun at distances exceeding half a mile. In case 
of danger of capture the gun is made inoperative by unscrewing the cap from one 
of the tubes and carrying it off, or by taking off the breech mechanism, which 
can be done in two minutes. 

The larger guns of this type may be used in countermining. Mounted for- 
ward on a ship they can clear a channel of all dangerous obstructions, exploding 
by concussion submarine mines as the ship advanced. This interesting gun is 
made by the Sims-Dudley Defense Co., 120 Liberty Street, New York. 



PORTABLE MOTOR. 



The development of the Stow Flexible Shaft affords an interesting example 
of the progress of the age of mechanics. It is used to operate drilling, tapping, 
reaming and grinding tools for portable work. 

It has gone through the experience of "rope drive" from any convenient 
shaft. Then electricity was adapted with fairly good results — the chief objections 
were expense, danger and the necessity of a skilled mechanic to run it. 

A Compressed Air Motor is now employed and embodies the required 
convenience and economy. , 

The motor is mounted on wheels so as to be moved easily from one point 
to another. The following description of its general construction will show its 
adaptability to machine shop works. 

The motor complete on its base, as shown in Fig. 444, in which one side- 
plate has been removed to show the interior construction, weighs 300 lbs, and oc- 
cupies a space 20 inches long, 18 inches wide over wheels and 19 inches high. 
With an air pressure of 80 lbs., it is capable of developing 8 horse power. It is 
provided with a 6-ineh pulley (P) on one end of the shaft, while at the other 
end is a projecting counter-shaft capable of running at two speeds, and on which 
can be slipped a patent universal joint flexible shaft coupling. 

With a pressure of 80 lbs. the maximum speed of the engine is 1,400 revolu- 
tions per minute. 

The construction of the motor is extremely simple, and consists of a sub- 
stantial cast-iron base plate 20x14 ins , Fig. 445, upon which, in a water and dust 
tight box, 12H X 7^/^ x 13 7-16-ins., are two small oscillating cylinders, having 
a diameter 3 inches and a stroke of 3 inches. The two piston rods connect directly 
tc a solid forged shaft, iH inches in diamater, which has three good-sized bear- 
ings, two in the end plates, and one in the center column, which is cast with the 
bed plate. This column also contains the inner trunnion bearings for the cylinders, 
and into its top is screwed a heavy lifting ring, which is used to support the motor 
over the work when desired, or it can be used to transport the motor about the 
shop if there is a traveling crane. The outer trunnion bearings are in the end 
plates, as will be seen in both figures. 



1 056 



USE. 




FIG. 444 — STOW FLEXIBLE SHAFT AND MOTOR. 

The back of the cylinders, corresponding to the cylinder head, is turned i| 
concentric with the trunnion to present a convex cylinder face to the valve block 
(B), which is a cast-iron block with a concave cylindrical face corresponding to 




USE. 1057 

the outer ends of the cylinders and containing properly-spaced inlets (S) and ex- 
haust ports (E). This valve block is held in place against the cylinder ends by 
suitable springs and adjustment screws. The gear case (G) at the end opposite 
the pulley contains two pairs of gears, a 2-in. and a 5^-in., and a 2^-in. and a 
5-in. The smaller gears are mounted upon the engine shaft, which is hollow at the 
end and contains a slip key, provided to lock either gear to the engine-shaft. The 
larger gears are firmly keyed to a short counter-shaft, from which power to 
operate the flexible shaft is taken. At the maximum speed of 1,400 revolutions per 
minute, there are, therefore, two shaft speeds, 485, TJZ, according to the pair of 
gears in operation, which is controlled by simply pushing in or pulling out the sHp 
key. Any other speed can be obtained by throttling the air supply, with, however, 
a corresponding reduction in power. While designed primarily to operate flexible 
^shafts, the motor is also arranged to take the place of any small engine, and the 
driving pulley admits of its use for a variety of purposes ; for example, it can be 
placed near and belted directly to a polishing machine, an emery grinder, brass 
lathe, etc. 

The motor is being built and introduced by the Stow Flexible Shaft Co., 
26th and Callowhill Sts , Philadelphia, Pa. 



THE HOUSTON PNEUMATIC TRACK SANDER. 

It is a well known fact that the amount of sand used by a locomotive is 
ordinarily three or four times that which is actually needed to perform the 
work, us the sand pipes running from sand boxes to rail are one and one-fourth 
(iJ4) inch diameter. Through these run a full stream of sand to the rail, fully 
75 per cent, of which leaves the rail before the driving wheels reach it, and is 
therefore wasted. 

Where sand is delivered to the rails by gravity only, you cannot accom- 
plish prompt and quick delivery of sand to rails when wanted. 

This device consists of a Siphon and Ejector, simple in construction and 
easily kept in order. It takes up the sand and forces it with great velocity in- 
stantly to the point. of contact between driving wheel and rail to either front or 
rear drivers of anj' type of locomotive. Distance from sand box to point of 
delivery can be any distance. 

The sand pipes used in connection with this device are very small, being 
only one-half inch, by which a close discharge and a neat and economical con- 
struction can be accomplished. 

Sharp angles in the sand pipe do not affect the flow of sand, as the strong 
air blast forces the sand through them, and to any distance. 

The Siphon and Ejector used in connection with this device are especially 
designed to give the sand a great forward velocity and momentum with a small 
. amount of air. 

The sand to both back and front drivers is operated by one valve in cab. 
This valve is of a very novel construction and is designed so as to regrind itself. 

It is claimed that this device will save 75 per cent, of sand in ordinary 
usage, and much better results have been attained on some roads. 



1058 



USE. 



The feature of giving sand to both front and rear driveis from one box 
is well worth considering. 

It can be applied to an engine in six hours by two men, and is applicable 
to old boxes as easily as to new ones. 



THE FOSTER REGULATOR. 

The frequent inquiries we have for pressure regulators have led us to show 
the illustration herewith, which is a view of the Foster combined pressure . regu • 
lator and automatic stop valve for high initial air pressure. This valve h^s been 
used successfully in various experimental works and in connection with some ^ 
very important ones where high pressures were employed. 

Probably the most difficult problem to solve in connection with the use of 
high initial air pressures up to 3,cco lbs., in order to make it commercially suc- 




FIG. 446 — FOSTER PRESSURE REGULATOR. 



cessful, is the automatic regulation of the air so as to maintain a constant uniform 
delivery pressure against a variable initial pressure, which may be at any point 
between 150 and 3,000 lbs. on the square inch. 

The operation of a reducing valve is controlled by the delivery pressure 
acting on a diaphragm or its equivalent, against a spring or its equivalent. It 
will, therefore, be readily understood that with an initial pressure of 2,000 or 3,00c 
lbs. the valve may not have to open more than one or two thousandths of an inch 
ir order to give the necessary delivery. 

A is the regulating valve, B an auxiliary valve, and C the stop valve! Air 
is admitted through pipe 16, and passing through the stop valve enters the regulat- 
ing valve (which latter is constructed on principles similar to the regular Class 
W), and is delivered at pipe 17. The delivery pressure entering the diaphragm 
chamber of the regulating valve, passes through pipe 9 and strainer D to the 



USE. 1059 

auxiliary valve, which is controlled by a diaphragm operating against the spring 
contained in the casing 4, the pressure of the spring being regulated by screw 5. 
If, for instance, the regulator is set to deliver 100 lbs., and the discharge pressure 
should be shut ofif, the tendency would be to increase the discharge pressure in 
pipe 17, if there should be any leak through the regulator valve. This pressure 
acting on the diaphragm in auxiliary valve B, will, when it reaches say 120 lbs., 
open the valve and allow the air to pass through pipe 10 to a diaphragm chamber, 
18 in stop valve C. The area of this diaphragm in stop valve C is sufficient to give 
about 12,000 lbs. pressure, which, operating on a steel beveled plunger, forces it 
into its seat with power enough to make a crushed joint on the valve seat, thus 
effectually closing off the flow of air. When this delivery pressure falls to its 
normal condition, say 100 lbs., the spring in casing 4 opens the auxiliary valve and 
allows the air in the diaphragm chamber of the stop valve to exhaust through the 
small ports 3 into the air. The initial pressure then acting upon the steel plunger 
forces the stop valve open. 

In a recent test of this valve where there was frequent stopping and starting 
of an air motor, it was found that the stop valve automatically closed off the air at 
every stop of the motor, and immediately opened when the motor was started. 

The device is self-contained, as shown in the engraving — the connections 
between the stop and regulating valves being made up with crushed joints, held 
in place by two rods, 14, clamping the two end pieces, 15, together. 



THE CLEANING OF CARPETS. 

One of the complications peculiar to life in large cities is the difficulty that 
besets the householder when he desires to have his carpets cleaned. The old- 
fashioned way of shaking or beating them from the windows is prohibited in most 
large cities, and the alternative of taking them to the fields is, for various reasons, 
cut off. Brushing will serve for a certain period, but in time a more effective 
treatment becomes imperative, and experience has long since shown that, unless 
the work is conducted with great care and method, the cleaning process may be 
as destructive as that of the Indian dhohi or washerman. The weight alone of 
many carpets renders the most careful handling necessary, and if the carpet be 
valuable as well as old, it may suffer serious deterioration in the process of clean- 
ing. The original method of cleaning carpets was carried out with the aid of 
sticks, handled by laborers, and lubricated with beer — for the job was a very 
thirsty one. It was carried out in the nearest convenient field, and if there was 
any wind, the dust went with it; if not, the beaters were enveloped in a very 
unwholesome cloud. Sticks would occasionally go through the carpet, and it gen- 
erally returned from the cleaning a good deal the worse for wear. The first 
attempt at mechanical dry cleaning was made with a machine something like that 
used for beating rough cocoon silk waste after washing. Next, a fan was added to 
carry off the dust; then leather beaters superseded the sticks, and finally com- 
pressed air was employed in numerous fine streams, which without the least 
violence seems to drive out every particle of dust in any carpet, however dirty. A 



io6o USE. 

visit to the headquarters of the Patent Steam Carpet Cleaning Works at York 
Road, King's Cross, London, will enable those who are interested in the subject to 
see the process in operation. 

The beating machine, by which the carpet is struck on the underside by- 
revolving leather beaters, will take in carpets 54 ft. wide and of any length. They 
are passed forward and backward through the machine until they cease to give off 
any dust, all the dust being carried off by an exhausting fan and discharged into 
a chamber where it meets the exhaust steam from the engines. The effect of the 
steam as it condenses on the particles of dust is to increase the weight of the dust 
and cause it to fall to the ground. The workmen attending these machines pass 
their days in a clean atmosphere, the current passing them to enter the machine. 
The compressed air machine is the latest improvement which, as has already been 
stated, dispenses altogether with beaters. A powerful pair of engines, capable of 
developing 200 horse power, is used to drive the air compressors which provide 
the air supply at a pressure of 70 lbs. per sq. in. The air escapes from a row of 
jets in a pipe striking the surface of the carpet and dislodging all the dirt. 
The cleaning machine itself is a very simple affair. The carpet is passed over a 
long cylindrical roller built like a cage. Above this cage, at a distance of about 2 
inches, is suspended the jet pipe, parallel with the roller. The pipe has a short 
back-and-forward movement communicated by the engine, and the carpet passes 
slowly over the roller beneath the vibrating jets of air. An exhausting fan carries 
of^ all the dust and the air from the jets to a chamber where steam precipitates all 
the solid particles. The process is continued until when struck with a rod the 
carpet gives off no dust. In this manner the most valuable carpets may be 
cleansed without risk of injury to their texture. 

The company have works at Manchester, Leeds, Dublin and Glasgow, as 
well as in London. This process has an interest which extends far beyond the 
business of carpet cleaning. It will doubtless find further application in the sepa- 
ration of dust and dirt from many materials, and it points to means for the reduc- 
tion of the offensiveness and unwholesomeness of many trades which at present 
have to be segregated. There is a distinct relationship between the carpet clean- 
ing process and the more recent one for cleaning railway carriages with an 
air brush, which works with extraordinary rapidity, and neither wears the 
linings nor rubs dirt into them, as is the case with the hair brush. Com- 
pressed air has, during the last few years, been recovering from a damaged 
reputation acquired through misuse. In many cases it was used at excessive 
pressures, at other times the pressure was too low. The methods of compressing 
ir were also defective. It is now used successfully for a great variety 
of purposes, including the driving of underground machinery in mines, propelling 
tram cars, driving cranes and machine tools, rock boring in tunnels, pneumatic 
transport, cooling stores of perishable merchandise, etc. For the transmission 
of small powers in factories compressed air is most convenient. It needs no 
exhaust pipes and no covering on the conduits. Its efficiency is greatly augmented 
by being heated before use in motors, but the heat must be supplied immediately 
before use, as hot air cools very rapidly in pipes.— T/i^ Indian Textile Journal 



USE. 



1061 



PNEUMATIC CARPET RENOVATOR. 

Interest has been aroused by an invention for cleaning carpets and we 
herewith illustrate the device itself and the method of operating it. 

The carpet renovator, which was recently designed and patented by J. S. 
Thurman, formerly M. E. of the Mo. Pac. Ry. system at St. Louis, Mo., consists 
of a box or receptacle into which a blast of air is injected in the shape of a fan. 
The blast of air striking the carpet throws the dust through the tortuous passage 
and deposits the dust on the inside of the box; that dust, which is lighter than 



;',/, » . 




^ 



JU|. SMOVStHO '/AETHOP OF OpERATlNq TWt CARVET CLtANER . 



FIG. 447 — SYSTEM OF CLEANING CARPETS WITH AIR. 



air, is caught by a screen before the air is exhausted into the room. The dust col- 
lector is about 8 in. long by 5 in. wide by about 6 in. high, and the blast of air is 
1.64 in. wide by 8 in. long. This dust collector is pushed back and forth over the 
carpet by an operator and collects from 98 to 100 per cent, of all the dust that the 
carpet contains. 

The source of air supply is obtained by compressing air into bottles or 
Mannesmann tubes at 2,500 lbs. pressure. These bottles are filled with com- 
pressed air at a central plant, and equipped with machinery specially designed to 



io62 



USE. 



compress air to a high pressure. On these bottles are attached a reducing valve to 
reduce the air from 2,500 lbs. to 50 lbs. per sq. in. The bottles, after being filled 
at a central plant, are delivered to the sidewalk in front of the residence to be 
cleaned. The hose is then connected to the reducing valve on the bottle and the 
other end of the hose taken into the house and the dust collector is attached. The 
dust collector is then run once over the carpets, which is sufficient to cleanse them 
of all dust and restore the carpet to its natural color. Before the carpets are 




FIG. 448 — DETAILS OF CARPET CLEANER. 

cleaned the walls are cleaned and also the tapestries and cushions. It requires 
only about two hours to clean a nine-room house, and the charge will be nominal. 
By the present method carpets are taken up and removed to a cleaning 
establishment, which requires three to four days, while with compressed air the 
work is accomplished in a far better and more satisfactory manner in two hours. 
In other words, the husband leaves home in the morning and when he returns 
in the evening the home is cleaned. 



J 



1 



USE. 



io6- 



MECHANICAL HOUSECLEANING. 

Some months ago there was described in these columns a device known as 
the "House Renovator," which is a dustless system of cleaning, renovating and 
disinfecting hotels, residences, office buildings, hospitals and public institutions 
with compressed air. The scheme in general is not entirely new. Railroads have 
been cleaning their passenger and sleeping cars with compressed air successfully 




FIG. 449 — HOUSE RENOVATOR. 



during the past ten years, but the device mentioned is designed for the purpose of 
not only knocking the dust and dirt out of their lodging places, but to imprison 
them before they have a chance to obtain another habitation. 

We all remember, nay, observe, the patient houseworker with a broom. 
She goes after the particles that lurk in the woof of the carpet and to give her due 
credit she gets many of them, but it's a wearing process and ends up with a lame 



io64 



USE. 




FIG. 450 CLEANING CARPET BY COMPRESSED AIR — ELECTRIC AIR COMPRESSOR. 

back. The filmy dust picks out dark furniture, and children write their names in 
juvenile glee. It is further pursued and battered from one place to another, until 
somehow or other it gets out of sight again for awhile. After awhile the accumu- 
lations multiply and then comes housecleaning. 

Here is where Mr. Thurman, of St. Louis, steps in. He claims not to dis- 
turb your carpets. By his system the walls are cleaned of all the dirt and dust, 
the carpets are thoroughly renovated, removing and collecting all the dirt and 
dust the carpet contains, also removing that dirt which is between the carpet and 
the floor. After the carpets are cleaned they are thoroughly disinfected, the dis- 
infectants being blown on the walls and into the carpets with compressed air. 



USE. 



1065 



The process has many features which appeal to every one. The lessening 
of tiresome labor and the purifying of the atmosphere of living apartments arc 
among the important ones. 

By this method one man can clean from eight to twelve rooms per day, 
which includes walls, carpets, rugs, draperies, bedding and upholstered furniture. 

Fig. 450 shows the system operating in hotels, using an electric air com- 
pressor mounted on a rubber-tired truck in which the power is supplied to oper- 
ate the compressor from the electric light wires. This machine compresses air up 
to 90 pounds per square inch and stores the air in the air reservoirs mounted on 




FIG. 451 — CLEANING CARPETS OF PRIVATE HOUSE. 



the truck; the supply of air to operate the dustless carpet renovator is drawn 
from these reservoirs. The renovator is pushed back and forth over the floor in a 
similar manner to the ordinary carpet sweepers now in common use. The reno- 
vator collects all the dust which the carpet contains, and after the room is cleaned 
the dust is dumped out into a receptacle. 

Fig. 451 shows the system operating in private houses having no electric 
light wire connection, the supply of air being obtained from bottles. These bottles 
are made of suitable size and are rolled of a solid billet of steel, into which is 
pumped compressed air at 3,000 pounds' pressure per square inch. On the neck of 
these bottles are attached reducing valves, which reduce the air from 3,000 to 70 



io66 USE. 

pounds per square inch. These bottles are filled at a central station, using hi^h 
pressure air compressors, which are made especially for this company. These 
compressors are capable of filling from i8 to 20 bottles per day, and one bottle 
has sufficient capacity to clean five ordinary rooms and are tested up to 13,000 
pounds per square inch. After the bottles are filled at the compressor they are 
loaded on a wagon and are delivered on the sidewalk of the residences to be 
cleaned. The hose is attached to the reducing valve of the bottle and is carried 
into the house and furnishes the proper amount of air to renovate the carpets 
and collect the dirt and impurities therefrom, as illustrated. 

Mr. J. S. Thurman, the inventor of this system, has recently organized a 
company known as the General Compressed Air House Cleaning Company, and 
who are contractors and engineers for complete house cleaning equipment and 
compressed air plants, with offices in the Lincoln Trust Building, St. Louis. At 
the present time the company is arranging with parties who desire to get into 
this business in various cities and towns of the country, and are also arranging 
with hotels and institutions for the same purpose. 



THE KRAUSE AIR FILTER. 



A novel apparatus in the shape of an Air Filter has recently been patented and 
placed on the market by Mr. Arthur E. Krause, of 345 Fairmount Avenue, Jersey 
City, N. J. 

The object of an Air Filter is to prevent dust, grit, ashes, etc., and any im- 
purities from entering the intake in Air Compressors, Air Pumps, Blowers, and, 
in fact, all machinery handling air, and in which grit or impurities are detrimental 
not only to the operation of the machine itself, but also to the operation of such 
other machinery depending upon the first. 

Air filters have been tried at different times, but have been discarded on ac- 
count of the great amount of space taken in order to obtain adequate filtering sur- 
faces, and also for the reason that the intake pressure was considerably reduced 
below the atmosphere. 

Mr. Krause's Filter, which we illustrate herewith, is very simple and takes 
very little space. For instance, a filter suitable for a ij^" intake pipe would be 
only 6" dia. by 5" long, and such a filter can be attached to intake pipes for Air 
Pumps, Air Compressors, Blowers, Gas Engines, etc. 

The construction of the filter is as follows : Circular shaped flat bags made 
of felt, cotton, asbestos, or any other suitable material, with thin outer edges 
sewed together and having a concentric opening so as to obtain access to the 
interior of the bag from both sides. 

Into the interior of each bag there are inserted two flat ring-shaped washers 
made of sheet metal, one of these washers having protruding bosses stamped 
thereon, the other washer is perfectly plain. 

When placed within the bags the bosses of one washer are placed against the 
flat side of the other washer, thus making a separating space between the two 
washers, which serves as a free passage for any air filtered into the bag from 



USE. 



1 06 



the outside. After the washers are thus inserted within the bags, a certain num- 
ber of them are placed over the above-mentioned tierods, the number of bags de- 
pending upon the length of the supports and amount of filtering surface desired. 

After all of the bags are thus placed over the supports, a metal washer, or 
disc, having three holes corresponding to the position of the three supports, is 
placed over the bags, and the thumb nuts are screwed up against the disc, thus 
forcing the separate bags together at the edges of the central openings, so that 
perfectly tight joints are secured. 

There is no pressure exerted on any part of the surfaces of the bags, so that 
the air has perfectly free access to such surfaces, and after filtering through the 




FIG. 452 — THE KRAUSE AIR FILTER. 



bags from the outside, the air passes through the free space between the inside 
washers and into the interior of the body of the filter, from whence it is drawn 
off by the air pump or compressor entirely freed from dust or grit. 

It will be readily understood that this arrangement of the filtering bags will 
permit of a very extensive filtering surface within a very small space, at the same 
time allowing ample air spaces between the bags to render all of such surface 
effective and efficient. 

These filters can be cleaned or dusted while the machinery to which they are 
attached is in operation, or a new set of bags can be inserted in a few minutes' 
time. 



io68 . ■ USE. 

To show the great amount of filtering surface which can be obtained in a 
very small space, we want to say that a i^" filter, as constructed, would consist 
of 22 bags, each bag having on each side a surface of 15 sq. inches, making the 
total filtering surface 660 sq. inches, and the space occupied by same does not 
exceed J/^ of a cubic foot. Thus it will be seen that a filter covering one cubic 
foot in volume could have a filtering surface of 36 sq. ft. 

Of course the filtering surface depends not only upon the size pipe or open- 
ing, but also upon the quantity of air to be filtered, and upon the amount of dust 
or grit which may be contained in the air. 

Owing to the large air filtering surface the resistance to the inflow of air is 
hardly appreciable if the filter is dusted occasionally. 



AIR METERS. 



In one of the early numbers of Compressed Air we called attention to the 
fact that a reliable air meter for measuring air volumes was in demand. We 
have recently been informed that Mr. Clemens Herschel, the distinguished 
hydraulic engineer who designed the Venturi water meter, is prepared to apply the 
Venturi principle to air. There seems no reason to doubt that this meter, which 
has established its place as the simplest reliable means of measuring large water 
volumes, might apply equally as well to compressed air. A great advantage of 
the Venturi principle is that it does not retard the flow of the liquid or gas 
measured. Mr. Herschel, whose address is No. 2 Wall Street, this city, will 
take the details of this subject up with those contemplating its introduction. 



AIR MOTOR FOR COPENHAGEN. 

By the steamship "Hekla," of the Thingvalla Line, which has just cleared 
for Copenhagen, a full set of street-car equipment, consisting of compressor, stor- 
age tanks, valves, motor, etc., was shipped to a syndicate formed in Denmark for 
the introduction of air motors in Scandinavian countries, regarding which the 
following translation from a Copenhagen newspaper is interesting to American 
readers, who have not yet had the pleasure of seeing air adopted by any American 
street railroad, although it is understood that a number of contracts are being 
held open, pending the consolidation of the air companies : 

"Mr. Josephsen, as president of the Danish Air Power Co., has been work- 
ing with the Copenhagen authorities to bring about the use of air motors in the 
streets of Copenhagen for street car service, and to this end the Danish syndicate 
has arranged with the American Air Power Co., of New York City, for a full 
equipment, and in the meantime the company is acquiring the rights for the 
most desirable streets in Copenhagen." 



USE. 1069 

COMPRESSED AIR ON THE HOLLAND TORPEDO BOAT. 

A study of the John P. Holland Torpedo Boat Co.'s latest type of subma- 
rine boat convinces the student of naval architecture that she is light of draught, 
seaworthy as a cork, handy as a toy, and able to dive into the depths of the sea 
like a mackerel, and that from the standpoint of mobility and power of attack she 
is better than a battle ship and a torpedo boat moved in unison for attack upon a 
port or a fleet. The modern battle ship is a massive, floating fortress, embodying 
the ideas of military engineers, and the traditions of the naval constructors of 
Great Britain and France, who superimposed the Ericsson turret principles upon 
the broadside man-of-war of forty years ago. The torpedo boat of the best exist- 
ing type is merely an evolution from the bomb boats and powder ketches of fifty 
years ago,- whereas the Holland submarine boat is constructed in strict accord- 
ance with the latest improved ideas and inventions, all of which are combined to 
make her swift to execute the end for which she has been contrived. 

The science of submarine boat construction germinated when David Bush- 
nell, of Saybrook, Conn., in 1777, invented and built a craft which because of its 
shape he named, the Tortoise. In a letter to Thomas Jefferson, he stated that the 
craft was made habitable under water for twenty minutes, by the use of air 
pumped into two small copper cylinders, these cylinders were fitted with crude 
stop cocks, and placed as nearly as possible to the nose of the sole occupant of the 
craft, who navigated it by means of an oar. But one attempt to use the craft was 
made, and that turned out badly for the navigator and inventor. 

Bushnell afterward made an improved submarine boat, which met with 
public derision, but many years afterward his grand-son, C. S. Bushnell, of New 
Haven, Conn., adopted several of his grandsire's ideas in a submarine boat which 
he and John Ericsson built and offered to the government. It was rejected, then 
Ericsson began work on plans for a monitor type ship, and Bushnell by the force 
of his energy, induced the Navy Department, which was bitterly prejudiced 
against Ericsson, to accept the Monitor, subject to tests in battle at the expense of 
Bushnell and others, who furnished the capital that built and equipped her. 

Great was the surprise of the doubting Thomases of the navies of the 
world, when a terrible conflict thrust itself on the wooden fleet in Hampton Roads, 
and in the heat of battle with the Confederate knife aimed at her heart, Columbia 
saw by the light of three ships burned by the Merrimac, the Monitor, despised 
and rejected by nearly every navy, steam into the broad bay to achieve a glorious 
victory, save the capital of the nation from capture, and sound the death knell of 
wooden navies. 

Because the science of constructing compressed air apparatus was in a crude 
state in the days of the Civil War, Ericsson and Bushnell, were unable to accom- 
plish satisfactory result in submarine craft, and for lack of compressed air appa 
ratus.'the ships of the monitor type were almost uninhabitable. So naval science 
stopped short until in due season the advance of compressed air science by leaps 
and bounds gave naval architects a fulcrum on which to place a bar to lift a world 
of progressive ideas into perfect shape. The great defect of the monitor type was 
their crude system of ventilation that failed utterly at sea or in harbor; the 
excessive heat generated by the boilers, the rotting of the woodwork, and the gal- 



1070 



USE. 




USE. 107 1 

vanic action set up by the action of bilge water upon copper and iron fittings 
formed such a pest house as to render them more dangerous to life than the shot 
and shell of the enemy. 

Jefferson Davis in his account of the Civil War, states that submarine tor- 
pedo boats were the constant theme on the tongues and pens of the Confederate 
torpedo division, who sank fifty-eight Federal vessels and kept the blockading 
squadrons out of Charleston, Savannah, Wilmington and Mobile for several years 
by the use of torpedoes. Several sorts of submarine boats were built by these 
officers, but all failed to meet expectations ; one was sent out from Charleston to 
attempt the blowing up of Commodore Goldsborough's fleet ; but she was never 
heard of after setting out and diving beneath the surface. It was supposed by the 
Confederates, that the crude system of supplying air failed, or that the pressure 
of the sea burst in the sides of the boat and drowned the dozen men aboard. 

That was the last attempt at submarine work until more than twenty years 
ago, when Mr. John P. Holland, began a series of experiments with uor'^s of his 
own invention. These experiments have been continued by him from that day to 
this and have resulted in the boat now manceuvered by him in New York bay. 
The principles of construction are adapted for any required size and armament 
according to the requirements of purchasers. The existing boat tends to resemble 
nothing so much as a Salisbury dory inverted upon a Nantucket whale boat. She 
is 53 feet long, eleven wide amidships, and of seventy-five tons displacement. The 
hull is made of steel plates, riveted to a steel skeleton frame. Amidship is a 
conning tower so made as to extend from two to three feet high, or telescope flush 
with the hull. Within the hull, immediately below the conning tower, are the 
two rudders, one for surface sailing, the other to regulate the depth at which the 
boat is operated when submerged, and the speaking tubes, electric bells, and a table 
connected with apparatus for manipulating camera lucida, used when the boat is 
submerged for portraying the appearance of the surface for miles around. The 
view is secured by means of a steel tube thrust above the waters and fitted with 
camera apparatus. There are three sources of energy for propelling the boat above 
and below the water, expelling water, discharging torpedoes and dynamite guns, 
and lighting the ship internally and externally ; these sources are compressed air, 
gasoline and electricity. 

The most important agent is compressed air. without which it would be 
impossible to operate the boat five minutes under the sea. The air compressor 
which breathes the breath of life into the craft, is an Ingersoll-Sergeant Drill Co.'s 
single acting compressor, belt driven from a gasoline engine, when the boat is on 
the surface, and from an electric motor switched to a storage battery, when the 
boat is submerged. The compressor is capable of compressing air to 2.500 pounds 
pressure ; the diameter of the low pressure cylinder is 6 inches, the high pressure 
cylinder is i^-inch diameter, with 8-inch stroke. Both cylinders are immersed 
in a water box, which cools the air during compression. Solid discs serve for fly 
wheels. The space occupied is only six feet and five inches long, and two feet 
high. The highest value of the compressed air is for the respiration of the crew, 
numbering ten men. For this purpose the air is expanded through two reducing 
and one regulating valve, and is set free at the normal atmospheric pressure. 



I072 



USE. 



Six times the requisite volume of air is available ; the surplus air is used for 
counteracting the deleterious effects of the ventilating pumps, which would pro- 
duce a near approach to a vacuum, if the air supply from the tanks was interrupted 
in its even flow. The steering and diving gear are operated by compressed air, 
which also maintains the air pressure throughout the boat to equalize the pressure 
of the sea when the boat is submerged. The boat is quickly submerged by admit- 
ting sea water to a series of steel tanks connected with the compressed air system'. 
A dive of 40 feet below the surface is made with safety and comfort in a minute. 
When the commander signals to elevate the boat from the depths, air is forced 
into the water tanks under high pressure, and as the water is expelled the boat 




FIG. 454 — HOLLAND BOAT DIVING. 



rises swiftly to the surface. The air tanks have been tested to stand a pressure of 
3,000 pounds to the square inch, and are calculated to hold out for a submergence 
lasting ten hours, but if the supply should fail after nine or ten hours, the tanks 
can be replenished by means of a tube projected to the surface as a suction pipe. 

The armament of the boat consists of one dynamite gun, one automobile tor- 
pedo tube, and one aerial torpedo tube. These tubes and gun are made terrible 
engines of propulsion of projectiles by the power of compressed air, which not 
only enables the torpedo and gun operators to hurl torpedoes and great masses of 
dynamite with deadly precision and irresistible force, but immediately restores 
to the boat the weight of 800 to 1,000 pounds lost when a projectile or mass of 
dynamite is discharged. The muzzle energy of the dynamite gun is 750 tons, a 



USE. 1073 

force powerful enough to crash through the bottom or below the water line of the 
mightiest battle ship afloat, and send her hurling to the bottom of the sea in the 
twinkling of an eye. 

Like nearly all valuable inventions in the domain of naval science, the 
Holland boat represents a series of long continued experiments conducted by 
civilians contending with numerous difficulties, and she is an embodiment of the 
belief of the most advanced naval architects, that from the latest achievement in 
submarine engineering, the battle ships and cruisers are at the mercy of the sub- 
marine boat that lurks beneath the sea, noiseless, and as swift to strike deadly 
blows as the sword fish which steals under the mighty carcass of the whale, and 
with one lightning-like thrust of its sword reddens the sea with the blood of the 
mightiest monster of the deep, which with the churning of the waters, and a flip 
of its flukes, rears upward for a brief second and then plunges down to the utter- 
most depths of the sea lifeless and inert. 

Ere long the Holland boat may be tested in battle here or beyond seas, 
for war looms across the track that the ship of the world's progress is coursing; 
who can tell what lies in its bosom? But there is a sound heard from that direc- 
tion which tells us it will not be the unarmed or the weak nation that will fare best 
when the thunderbolts crash from the war clouds. 

War has endured through thirty centuries recorded by history unchanged 
or unchangeable; it rests as solid as the bottom of the sea, uninfluenced by the 
motion of the waves of time. Pugnacity and warlike tastes are as strong in the 
masses of mankind to-day as at any time in history, and the predominant spirit 
of several highly civilized nations is the policy of war, victory and domination. 

G. WILFRED PEARCE. 



PNEUMATIC PLANER FEED. 



There has been patented recently by Alexander Gordon, president of the 
Niles Tool Works Co., Hamilton, Ohio, an application of air in the operation of 
planing machines which will be of advantage to that type of machines and add 
to their efficiency. In this device the feed is actuated by air. It is positive and 
reliable, and has a very wide range. A quicker return than ordinarily obtained 
is desirable. By operating clutch pulleys by air, any desired speed is obtained, 
with mechanism which is very simple, has few parts, and none subject to ex- 
cessive wear. 

We illustrate herewith this pneumatic feed and quick return. The air is 
taken from the compressed air supply, such as is now in use for general machine 
shop purposes, or from a small pump that may be attached to the machine in any 
convenient position, and be driven by a belt from the countershaft. It is carried 
from the pump or compressor through a suitable pipe to air cylinder which con- 
trols the feed and driving clutch mechanism. 

A specially constructed valve admits it to the cylinder. This valve is 
operated through simple connections, fully shown in the drawings by the shifter 
arm and reversing tappets on the planer table. When the table carries the tap- 
pet or dog against the reversing lever, instead of shifting the belts, as in the ordi- 



1074 



USE. 



nary planer, it moves the valve lever controlling the air admission to the cylinder. 
This instantly throws the piston in the cylinder to the opposite end, carrying the 
rack to which it is attached forward or backward to operate the feed rack. 
xA.t the same moment the clutch operating the worm shaft is thrown over and 
the direction of the table motion is reversed. This shifting arrangement is sim- 
ple and efficient. 

By examining the drawings it will be noticed that the piston rod is carried 
through the cylinder toward the back of the planer and is connected to a lever. 
The opposite end of this lever is attached to a rod running across and under the 
bed to the worm shaft. On the worm shaft end of this rod is a segment gear 
whose teeth work into a short rack. The rack is attached to a rod which moves 
the central member of the clutch from one pulley to the other, and the. pulleys 
are operated one by straight and one by cross belt. 

Fig. 455 shows the clutch pulleys, bearings, sleeves, casing and also 
the clutch shifter rod in the interior of the worm shaft and clearly 




FIG. 455 — PNEUMATIC PLANER FEED. 



shows the various features of these parts. The belts run continuously in one 
direction, thus preventing the excessive wear due to shifting, to overcoming 
momentum of pulleys and other parts, and to the rubbing of the edges of the 
belt in the shifter eyes. The belts can be made as wide as the necessities of the 
case require, not being limited by any of the conditions always prevailing in other 
planers. The clutch, from its peculiar construction, holds most tenaciously 
under very slight pressure, and is quite easily released. 

No adjustment is required in keeping the clutches in working order, as 
they will do their duty until the wood facing is entirely gone, and the replacing 
of this facing or lining will not cost nearly as much as the repairs to and the 
replacing of belts. 

This is an effective machine for variable speeds, as the pulleys controlling 
the cutting speed can easily be made cones and belt shifted, as on a lathe. The 
pulleys operating the return stroke could also be made in this manner, and the 
speed increased or decreased, as the piece being planed was very heavy or very 



USE. 



1075 



light. The return may be made 6 or 8 to i, with air cushions positively pre- 
venting all shock. 

A number of these planers, from 30 x 30 to 10 x 10 inches, are in successful 
operation at the Niles Tool Works, and a 54-inch planer, for planing locomotive 
frames, with 35-inch traverse of table, is now under construction. The quick 
return on this planer is especially desirable by reason of its length and the com- 
paratively slow speed of the cut. — Iron Age. 



PNEUMATIC CHECK SYSTEM. 



What is claimed to be a valuable feature of protection to property is the 
Pneumatic Watchman Check and Regulator system, installed by the Pneumatic 
Watchman Check Co., of Columbus, O. In this system, what is called the clock 




FIG. 456 — PNEUMATIC PUSH BUTTON. 



or Recorder, is generally placed in the office of a plant or property, and the sta- 
tions are located at various places about, inside or outside, it is desired the watch- 
man to go when upon his rounds during the night. Each and every station is 
connected to the Recorder in the office by means of a small metal tubing, the size 
of a wire. This tubing is a composition of lead and tin and zinc, there is nothing 
about it ever to rust, to corrode, or to be affected in any way by the conditions of 
the atmosphere, or by heat or cold. The stations themselves are small iron boxes 
about three inches high. A sectional view of one of them is given in Fig. i. 
Inside of this iron box is a rubber ball made of a special composition or rubber, 
designed especially to stand the hard usage which it must undergo. The watch- 
man^carries a key which is in the shape of a tube with a button or knob upon the 
end of it. He inserts this key into the station and as he docs so, it pushes down or 
compresses the rubber ball upon the inside, and as he thus compresses the ball, it 



1076 



USE. 



forces the air through the tubing into the clock. The station may be located as 
much as 2,000 or 3,000 feet away from the clock, or it can be placed at one or two 
feet away. 

Inside of the Recorder is a set of corrugated diaphragms, made of german 
silver. A section of one will be noticed in Fig, 456. As the air is forced from 
the station through the tubing into such diaphragm, it causes the diaphragm to be 
inflated and rise up. On the top of the diaphragms is a small rod into which is 
screwed a needle and as the diaphragm is forced up by the air, it pushes the needle 
up, and in so doing, the needle punctures a paper dial, which dial is turned by a 
clock movement. Thus at any minute, day or night, whenever a key is placed into 
a station, it immediately forces the air through the tubing into the diaphragm, 
and this causes the needle to puncture in the proper spaces upon the dial show- 




FIG. 457 — RECORDER. 



ing the number of the station and also the minute it has been operated. A station 
may be operated any number of times. Fig. 457 is a sectional view of the Recorder. 
In the bottom of the Recorder is located the frame containing the diaphragms. 
Just above them is a deck or partition which covers over the diaphragms. On top 
of this deck is fastened the clock movement, which revolves the paper dial, keep- 
ing the time, the same as a clock, only there are no hands like in a clock. The 
whole dial face revolves. This machine, besides being used for the purpose of 
checking the movements and keeping a record of the night watchman, is also used 
m newspaper ofhces, to keep track of the form as it goes from one department to 
another. The Recorder is generally placed in the business manager's office. 
Ihere is a station located in the composing room, one in the stereotyping room, 
one in the press room, and another in the circulation department. When the 
form leaves the composing room, the workman there simply presses a key into the 
station located at such place and immediately it makes a record to the exact 



USE. 



1077 



minute on the paper dial in the Recorder in the manager's office showing just 
when the form left the composing room. When it is received in the stereotyping 
room, the workman there presses the station in that department. Also when the 
form leaves the stereotyping room, it shows when it was received and when it 
left such department. The same also in the press room and the circulation 




FK;. 458 — ANOTHER T> I'E OF RRCORnER. 



department. This machine has been placed in newspaper offices throughout the 
country. Besides being in operation in hundreds of factories and manufacturing 
establishments throughout the country, it is also used by railroads in their 
freight stations and also in their shop properties wherever night watchmen are 
employed. 



CHIMES. 

For a few years past chimes in church towers have been coming into favor. 
A number of cities in European countries have orchestras of this kind, that date 
back to the 17th or i8th centuries. There arc several in this country and every one 
of them have had the problem of how to ring them to contend with. This question 
has been so filled with obstacles, that even after the bells were bought and hung 
in place they have remained silent. 



I078 



USE. 



Pious persons of wealth knowing of no other lasting gift to make their 
favorite church, have bequeathed or presented chimes, leaving the ringing of them 
to the church itself. We know of one case where there are 44 bells and no music 
has been obtained from them, although they have been in place for many years. 
The ringing of chimes is a work, however, that is never wholly abandoned by 
church trustees, consequently, some of these churches have erected crude appli- 
ances, that ring the bells in a more or less satisfactory manner. Electricity has 
been the hope of many, and there are places where bells are rung by electric 
appliances, but they have never proved satisfactory. The chime bells of St. 
Germain-L'Auxerrois, in the city of Paris, were finished in 1878. Their con- 
struction extended over a period of 15 years, and yet they never rang successfully 
until a few years ago. To show the system employed in that instance, we present a 
picture of the key-board, cylinder and mechanism of these chimes. The system 
as a whole occupies a space of no less than 60 ft. in height, and an octagonal sur- 
face of 108 square ft. The weight room is 19 ft. in height by iij^ in width. The 
cylinders of the bell weights have diameters varying from 10 to 52 inches; each 
cylinder with its wheel work, accessories, and striking train constitutes a true 
dock. 

One of the finest set of chimes in the United States is that of St. Patrick's 
Cathedral, Fifth avenue. New York City. Nineteen bells constitute the set, and 
they were donated by Cathedral Parishioners and others. 



THE FOLLOWING LIST GIVES THE WEIGHT AND TONE OF EACH OF THE BELLS, AND THE 

NAME OF THE DONOR. 



Name of Bell. 



St. Patrick 

Our Lady's 

St. Joseph 

Holy Name 

St. Micbael 

St. Ann 

St. Elizabeth 

St. Augustine of Hippo 
St. Anthony of Padua.. 

St. Agnes 

St. John Evangelist. . . . 

St. Bridget 

St. Francis Xavier 

St. Peter 

St. Cecilia 

St. Helena 

St. Alphonsus Liguori , 
St. Thomas Aquinas . . , 
St. Godfrey 





Weight 


Tone. 


IN 




Pounds. 


B flat . . . 


6,300 


C 


4,400 


D 


3.300 


E flat . . . 


2,600 


E 


2,200 


F 


1,850 


G 


1,300 


A flat . . . 


1,100 


A 


965 


B flat . . . 


770 


B 


660 


C 


550 


C sharp. 


460 


D 


385 


E flat . . . 


330 


E 


275 


F 


220 


F sharp. 


200 




165 



Donor. 



Cathedral Parishioners. 

John B. Manning. 

Joseph J. O'Donohue. 

'J'he Sodalities of the Holy Name throughout the 

city. 
Michael S. Coleman, 
Henry McAleenan. 
The Marquise San Marzano. 
Augustine Daly. 
In memory of Edward Fox. 
In memory of James Edward Fox. 
John D. Crimmins. 
In memory of Aloysia Miniter. 
The Catholic Club. 
George B. Coleman. 
Mrs. Thomas F. Ryan. 
Eleonora Keyes. 
Maria A. Mills. 
Thomas Kelly. 
In memory of John and Mary Koop. 



These bells hang in the northern spire of the Cathedral, 180 feet above 
ground. The following ritual of the bells is observed. The Angelus is rung 
at 8 a. m., 12 m. and 6 p. m. daily, and the De Profundis bell is rung daily at 
7 p. m. The chimes play on Sundays and greater festivals or national holidays, 
and pious occasions. The bells are tolled at funerals. 



USE. 



1079 



The same perplexing question arose when these bells arrived from France, 
where they were made. A committee was appointed by His Grace, Archbishop 
Corrigan, with Mr. Cornelius O'Rielly as Chairman, and Fathers Connolly and 
Lavelle, and Mr. John A. Sullivan as members. The subject was gone into 
thoroughly and all of the various systems examined exhaustively. Every one of 
the systems then in vogue seemed by this committee inadequate and lacking the 
modern facilities that marked almost every other method of doing things. The 
crudeness of methods, expense of installation and the necessity of having expert 
attendants caused all systems known to be rejected. Many propositions were sub- 




fig. 459 — keyboard, cylinder and mechanism of the chimes of st. germain- 

l'auxerrois. 



mitted. The bells were installed in the Cathedral spire in the autumn of 1897. 
In December, 1897, Compressed Air printed the following: "An inquiry comes to 
us asking for the services of some compressed air genius who can devise a prac- 
tical compressed air apparatus for ringing chime bells. A short time ago 19 
stationary chime bells, the heaviest of which is about 6,000 pounds, and the 
lightest about 300 pounds, were placed in St. Patrick's Cathedral, New York. 
It was intended to ring them by electricity, but thus far no device has been 
acceptable. It has been suggested that by a suitable installation compressed air 
would do the work satisfactorily. The church authorities will lend any assist- 
ance to enable experiments to be carried on, providing the plan submitted ap- 
pears feasible." 



To8o 



USE. 



This was the signal for work in this direction. Several compressed air 
experts came forward with sketches and designs to cover the requirements of 
these bells. The committee secured expert advice and finally accepted the system 
submitted by Mr. Hertford C. Champ, of New York, who had been a reader of 
Compressed Air, and who had made this subject his study. His plan was so sim- 
ple and embodied the essential features to such extent that this system was finally 
adopted and the work begun. The plan as installed consists of compressed air 
and electricity, the one being the motive power causing the bells to ring, and the 
other being employed as the means of operating the mechanism which strikes the 
bells. Chime bell ringing by compressed air had never been tried before, and Mr. 
Champ's genius has been severely taxed to complete a system that will in all 
probability be the most complete one ever used for this purpose. Following the 
proposition from the beginning we find a complete air-power plant consisting of 
an IngersoU-Sergeant, Class "E" compressor, with air cylinder 8 in. diameter by 
8 in. length of stroke, driven by a 15 H. P. 240 volt direct current six 
pole type Lundell motor, made by the Sprague Electric Co. These machines 
are rigidly mounted upon a heavy cast iron base plate designed and finished in Mr. 



2 3 -f? £ e 7 s ^ /4? // /^ 



I 



J b.i J J 



xJJ I ^ "■' 



4^ 



/3 



/^5" /O /7 /8 ^7 



1 l^-i hJ U n -1 ti-l 1 =] 


\-2 \ ! \ 



FIG. 460 — CHIMES OF ST. PATRICK'S CATHEDRAL. 

Champ's shop, and set on a rock foundation in the sub-basement of the Cathedral 
Rectory. The armature of motor is fitted with a pinion meshing into a cut spur 
wheel fitted on one end of the compressor crank shaft. This power unit is consid- 
ered extremely compact in its dimensions, runs remarkably well, and is capable 
of supplying the equivalent of 69 cubic feet free air per minute, which air is taken 
from a deep and decidedly cool area-way alongside the power room, and is 
delivered into a receiver 6 feet high by 24 in. diameter, from which latter the air 
power is conducted through a 2 in. pipe a distance of 600 feet to another receiver 
in the belfry. The two receivers have sufficient storage to at all times cause the 
bells to ring when they are wanted. Air is compressed to 80 pounds, so that there 
is always surplus for any emergency that may arise. A 2 inch pipe is carried as a 
main line, passing under each bell. From this main supply pipe, which is of itself 
a reservoir of air, ^ in. connections are made with the striking mechanism. After 
we have compressed the air we find it within 2 inches of the piston that moves 
the clapper to strike the bell. The key-board is located in the sacristy of the 
church. A cable is led to the church spire, and wires are connected to the magnet 
of the striking mechanism. Both the powers are here controlled from a distance. 



I 



USE. 1081 

The operator at the key-board presses a key corresponding to the bell that he 
wishes to have struck. This makes an electric connection which serves to open a 
valve admitting compressed air to a piston connected with a clapper which strikes 
the bell. Electricity is the trigger and compressed air the power in this work. 
There can be no measurable delay in the stroke. A duplication of this operation 
brings the nineteen bells under the control of the operator in the sacristy, where 
by means of the key-board showing the notes of the bells he rings the chimes to 
any air desired. The details as described show the practicability of this system. 



STERILIZED AIR FOR THE PRESERVATION OF FRUITS AND PRO 

VISIONS. 

What has become generally known as the "Perkins Process" for the con- 
servation of perishable products, opens a new field for scientific research, as 
well as the use of compressed air. 

The system attempts to — and so far the results prove it does — check the 
two prime factors of decay, viz., temperature and humidity. The latter has been 
almost entirely overlooked in present methods, and yet is of the greater im- 
portance. 

It is no unusual occurrence in the pure, rarified atmosphere of the Sierras, 
at an altitude of 3,000 feet and over, even at a temperature ranging from 80° 
to 100° F., to have fruit — noticeably the grape — ripen and without decay be- 
come thoroughly preserved on the stem. Hunters and miners keep their meats 
hanging in a tree, with the free air of heaven blowing around it and for weeks 
cut their delicious, full flavored steaks, until the whole is used. 

Following nature's course and guidance, after years of patient study, 
with chemical, microscopical and mechanical tests and experiments, the process 
has developed into a practical and effective service. 

A brief article could not do justice to the treatment, from a scientific 
standpoint, of the subject of decay in animal or vegetable life. The Q. E. D. 
that a new life comes into existence on the death of every old one, is positive. 
The delicate peach hangs a perfect picture of beauty on its branch, the ruddy 
blush half hidden among the glistening leaves. It is just ready to finish the 
ripening — the first stages of its decay. The warmth of the atmosphere and the 
sun's rays set the acid and sugar into fermentation; the carbonic acid gas 
developed pushes outward through the flesh, mellowing and fitting it for a lus- 
cious morsel, but at the same time carrying a viscid moisture to the surface, and 
there on the beautiful skin are the resting spores of the mycelium, awaiting the 
moisture and warmth to vitalize. After vitalization, there is the union of the 
hyphea, or the male and female spores, followed by the perfecting of fungus 
growth in root, trunks, branch, bud, blossom, and explosion of the seed bulb, 
sending its innumerable spores in every direction, to hasten the work of destruc- 
tion and decay on some other form of vegetable life. Clearly, then, perfect con- 
servation must regulate temperature, absorb moisture, dispose of the carbonic 
acid gas and impurities, and sterilize the growth of th*e fungus. 



io82 



USE. 



Compressed air under proper pressure is thoroughly sterilized, and one 
of the principal features of the "process" is the ingenious method by which the 
moisture is wrung, or rather separated from the air and deposited. 

At some future time we may note the construction an<i operation of this 
service for car and steamship transportation and for storage purposes. 

At Dr. Perkins' laboratory in Chicago, the tests for compression, expan- 
sion, friction, drying and sterilizing are developing new possibilities for other 
purposes than those the inventor at first intended. 

Although the "process" is in its infancy, machinery is being manufactured 
for the service in several foreign countries where the greater interest seems to 
be manifested in the introduction of improved methods for transportation. 



AIR BEDS. 

In this age of invention of labor-saving devices and improved appliances 
for our personal comfort, we are only too ready to attribute everything to the 




FIG. 461 — AN ANCIENT AIR BED. 



Spirit of the times, and we are quite surprised to find that something new, as we 
are pleased to call it, is really something old, and something very old at that. 
Take the subject of the sketch given herewith, Fig. 461, representing a view of 
an air bed dating back several centuries. This proves the air bed is not of 
modern origin. It was known to the ancients and apparently used. The illustra- 



USE. 1083 

tion is one of several figures attached to the first German translation of 
Vegetius, A. D. 151 1. It represents soldiers reposing on them in time of war, 
with the mode of inflating them by bellows. 

Heliogabalus used to amuse himself with the guests he invited to his ban- 
quets by seating them on large bags or beds, "full of wind," which being made 
suddenly to collapse, threw the guests on the ground. 

Although this case in point does not rival in importance the Colossus of 
Rhodes or Curios' Amphitheatre, holding 80,000 persons and built so as to swing 
about in the course of a few hours and form two theatres back to back, still it 
might serve to answer the question. What is new in the world? 



A CLOCK BY AIR. 



The new Fisher Building in Chicago is furnished with a clock run by com- 
pressed air. It is a monster time-piece on the eighteenth floor, and sets the 
hands on numerous dials throughout the building. This great clock is a sort of 
central plant, and it controls almost any number of secondary clocks or dials. 
Compressed air forms the connection between them. An air pressure of about 
fifteen pounds to the square inch is required, and tnat is usually obtained from a 
small air pump where other* compressing apparatus are not available. 

When the air pressure is turned on in the main pipe it exerts its pressure 
all over the building. At each dial there is a little air pocket, a simple escape- 
ment, and a couple of gear wheels. When the air pressure fills the pocket, the 
escapement starts and the hands move ahead one minute. Then the air is ex- 
hausted, the pocket empties, and the escapement sets itself ready for another 
impulse. In this way each minute sets the dials all telling the correct time ac- 
cording to the master clock. Hence the secondary time-pieces are never more 
than thirty seconds wrong, either fast or slow. 

In the Fisher Building there are now about twenty-five of these dials in 
use, and more are being added as fast as tenants arrive. 



SOMETHING NEW IN JAIL CONSTRUCTION. 

The "Pneumatic Safety Jail" is the significant name given to the latest 
design of steel jail cell recently perfected by the Pneumatic Safety Vault and 
Jail Co., of Chattanooga, Tenn. The inventors believe they have attained a 
greater degree of safety and security than is afforded by any other design of 
jail made, and, as the word "Pneumatic" would suggest, part of the means 
employed is compressed air. If the jailer has timely warning that the lock or 
door is being tampered with, or any of the cell bars are being cut or filed, he can 
always take measures to frustrate the intended escape. To give this sure warn- 
ing before any material damage can be done is the part compressed air plays 
in the new jail. The following description will convey an idea of its principal 
features of construction. The exterior walls of the cells are constructed of 



1084 



USE. 



vertical tubes with hard tempered steel cores, spaced about 4>^ inches between 
centres. The floor and ceiling are of double plates with an air space between. 
The horizontal bars through which the verticals pass are square in section and 
contain a small air pipe continuous all round the outer cell walls. An air pres- 
sure of 15 or 20 lbs. is maintained by a pump placed at any desired point in the 




JAIL CELL PNEUMATICALLY PROTECTED. 



building, the supply pipe connecting it with the air spaces of the cell being built 
in the walls of the building or otherwise protected. In small jails the pump is 
operated by hand and in large ones by electric or water motor or other available 
power. An automatic alarm, set to ring when the pressure fails to say 5 lbs., 
gives timely warning when any of the air spaces are pierced or connections 
broken. As may be readily seen the alarm can be placed at any desired point. 



I 



USE. 1085 

either inside or outside the jail building, or any number of alarms may be used. 
It may be conveyed to any distance by electricity or by air pipe, but the objection 
to relying on an electric alarm is that it may be so easily tampered with. There 
is no tampering with compressed air. An accidental loss of pressure, an injury 
to the supply pipe, any defect in the system must set off the alarm. The door is 
built up of tubes and receives the air pressure through tubular hinges or through 
a union near the lock, which must be disconnected to open the door. A flat lock 
of the Yale pattern is used, and as an additional safeguard, it is protected by an 
"Air Lock," which consists of a hollow hinged bar containing air pressure swing- 
ing across the door and face of the lock. This must be removed, thereby break- 
ing the air connection and sounding the alarm, before the lock can be gotten at. 
The cores of the vertical tubes spoken of above are octagonal steel about %-in. 
diam., tempered to be as nearly tool proof as such metal can be made. They 
are pivoted at the ends so they can turn loosely inside the tubes. The object 
being to give additional strength to the tubes, and in case of the air pressure being 
off for any reason, to make what the inventors believe to be a jail fully as dif- 
ficult to cut out of as any of the best designs now on the market. It would be 
almost an impossibility to saw or file through a bar built up of an exterior tube 
with a hardened steel core loosely fitted, that would turn with every stroke of 
the saw. And again, the temper of such a bar could not be drawn by any means 
available to a prisoner. Cases are numerous where the best so-called tool -proof 
bars have been softened so as to be easily cut, by what would seem to be the 
most simple means, unthought of by any one except a prisoner whose sole mental 
and physical effort is to get out, such as a blow pipe made of a common pipe stem 
and a candle allowed him by the leniency of the jailer, the one to read by and 
the other to smoke with; or piping gas across the cell to the desired point by a 
tube moulded of bread crumbs, etc. Shrewd criminals study the question of how 
to get out of jails just as the builder studies how to keep them in, and the con- 
test is close between them. It is like the contest between builders of war ships 
and makers of cannon, the one with his armor-piercing projectiles and the other 
with projectile-proof armor. It is an undisputed fact that unless closely watched 
even ordinary prisoners will find means to get out of the best built so-called "tool- 
proof" jails. We have but to watch the daily press reports to find numerous in- 
stances. In one of the most recently built state penitentiaries which has been 
finished scarcely two years, at least two escapes have been reported by cutting 
supposed tool-proof bars. Very recently a jail escape was reported in a promi- 
nent town of .one of the Eastern States that is in itself a unique example. Two 
prisoners cut the bars of their cells and laid in wait at night in the corridor for 
the one turnkey who was on duty. As he made his rounds they sprang upon 
him, bound him and left him helpless. Then they robbed the office safe of the 
jail of $2,500 belonging to various officials and prisoners, supplied themselves 
with revolvers and ammunition and made their escape. The manufacturers of 
the pneumatic safety jail believe they have introduced the only real improvement 
in jail building which has been made since the introduction of "Chrome" steel or 
of bars made up of layers of hard and soft metal rolled together. They have 
adopted the word "Safety" across a U. S. shield as a trade mark and believe it 
fully merited. Before offering to build jails for public use, they have experi- 
mented extensively to find what mechanical difficulties had to be overcome to 



io86 USE. 

be overcome to carry out their ideas. They have now a full size cell complete 
in every particular in their shops at Chattanooga. The principals involved and 
details of construction are fully covered by patents. Those principally interested 
in the enterprise are the Casey & Hedges Mfg. Co., of Chattanooga, well known 
manufacturers of boilers and machinery, and Linn White, an experienced civil 
and mechanical engineer, who will have charge of the business of the company. 



DUDLEY'S AIR GUN. 



It has been found that compressed air is the safest and best agent for 
expelling a dynamite shell. 

The "Scientific American," in a recent issue, describes the Dudley gun, a 
gun and compressed air plant in itself. It certainly is a most ingenious arrange- 
ment, and its use of gunpowder for the purpose of compressing air opens up pos- 
sibilities in the application of the principle which will be apparent to any skilled 
mechanic. 

The Dudley gun might be called a long tube, bent upon itself so as to show 
three tubes side by side. These tubes lie parallel to each other. The long cen- 
tral tube is the firing tube, and weighs 250 pounds in a 4-inch gun. 

The two side tubes might be called the air compressor, for it is in them 
that the air is compressed to 850 pounds to the square inch. At the forward end 
of the gun, the two outside tubes are connected by an air passage. 

The rear end of one of the tubes is connected by a similar passage to the 
central or firing tube, and the rear end of the other side tube is fitted with a suit- 
able breech mechanism to receive the powder cartridge. A glance at the diagram 
will show the passage of the air when the powder is ignited. 

The central or firing tube has a breech mechanism similar to a breech- 
loading rifle. In this the projectile with its load of high explosive is placed. 
Then the breech piece is locked, the poVder cartridge is placed in the side tube, 
and its breech is locked. 

The powder is ignited, and the air in the tubes is compressed by the gener- 
ate gases. The force of the explosion, cushioned by the two columns of air which 
are between the powder cartridge and the projectile, acts upon the projectile. 
The shell leaves the gun with little noise of explosion and no smoke whatever. 

The recoil of the gun is slight, and springs are provided for taking it up. 
The projectiles used in the gun are brass cylinders with pointed ends. The fuse 
is attached to the front end and from the rear end of the shell extend vanes or 
rings to insure rotation. The entire shell is 52 inches long, and when fully 
charged weighs 32 pounds. 

In the main body of the shell, which is the brass cylinder, the dynamite or 
nitro-glycerine is placed. In the forward end of the charge is placed a charge 
of gun cotton, and in the centre of the gun cotton is a case containing fulminating 
mercury. 

It is believed that the principle of compressmg air by the explosion of gun- 
powder, as it is done in the Dudley gun, can be employed in the useful arts, par- 
ticularly in quarrying and tunnel work, where air drills are remote from the 
main pipe of the air compressor plant. 



USE. 1087 

A NEW BOLT THREAD CUTTER. 

An appliance for cutting bolts and threads has been invented by Mr. J. H. 
Ferguson, Asst. M. M. of the Meadow Shops, P. R. R., Jersey City, N. J. 

The inventor claims that his device is to provide an automatic attachment 
for the feed portion of a bolt machine, by which the bolts to be threaded are de- 
livered, and when the threads are cut, removed from the "die holder" of the 
ordinary type of bolt threading machine, automatically, and much more rapidly 
than the usual method. The attachment also automatically opens and closes the 
dies, it being only required of the operator to lift the bolt out when it is cut, and 
replace it with one to be cut, thereby greatly simplifying his labor, and necessary 
skill. 

The means for accomplishing this result are, first, compressed air acting in 
a cylinder fitted with a piston and piston rod ; second, a valve and connection for 
automatically controlling the admission of air to either end of the cylinder ; third, 
a rigid bed, secured to the original bed of the machine, and to which the cylinder 
is fastened; fourth, a sliding plate, having a longitudinal motion, on the bed 
parallel to the axis of the die shaft, and being rigidly connected to the piston rod ; 
fifth, a round turret or monitor, revolving on the slide plate, being so revolved 
(when the slide plate is moved by the action of the compressed air in the cylinder) 
by means of a latch, engaging in pins which are set in a disc on the under side of 
the side plate, the disc, through the medium of a square bolt, revolving the turret ; 
sixth, a locking device for securing the turret in a certain position during the cut- 
ting of the bolt, yet permitting it to turn when the latch engages the pins ; sev- 
enth, the bolt holders in the turret, for securely holding the bolts in a proper posi- 
tion for cutting the threads, and allowing them to be easily removed and replaced; 
eighth, the substitution of a vise for holding work too long for the turret, the tur- 
ret being removed. 

When the compressed air is turned on, it starts the machine, the die holders 
revolving as usual ; the air entering the back of the cylinder, acting against the 
piston, forces the slide forward, and presses the bolt (held in the turret) against 
the dies which begin to cut the thread. As the thread is being cut, the valve plug 
is gradually turned until air is admitted to the opposite end of the cylinder, and 
tends to pull back on the slide ; therefore, when the die holder opens, the slide 
moves back, the lock pin is withdrawn, the turret turned, until a new bolt is 
brought into line, the die is closed, and the valve plug again admitting air to the 
back of the cylinder, a fresh bolt is forced to the die, the bolt just cut is then lifted 
out and another substituted, and there are always five uncut bolts in the turret. 



FIRE ALARM WHISTLE. 



Suburban towns that use fire alarms will be interested to know that the 
Compressed Air Whistle is the most effective means of proclaiming fire tidings 
that there is; and also that it is economical and automatic, and easy to install. 
Our correspondent, Capt. W. B. Sayre, says: "We have had a compressed air 
whistle in operation now about a year and find it a great success and eminently 



io88 USE. 

fitted for use in suburban villages, inasmuch as the cost is less than that of pur 
chasing and mounting a heavy bell, and the alarm is a hundred times more 
effective for the simple reason that the ear becomes accustomed to the sound 
of a bell owing to adjacent church or school bells, and if a person living sot 
distance from the engine house is sleeping soundly with windows closed a d 
wind blowing outside, he probably will not be awakened, but the hideous scream- 
ing of our siren will almost wake the dead, as under ordinary circumstances 
when the wind is not very high, it can be heard a distance of from five to eight 
miles distinctly, while it is doubtful if a two thousand pound bell would carry 
that far. Our plant consists of a boiler, an iron cylinder, eight feet long and 
forty-two inches in diameter, and capable of carrying one hundred and fifty 
pounds pressure. It is placed on the second floor of our engine house so as to be 
near the whistle and thus avoid unnecessary piping and probable leaks. It is 
fitted with pressure gauge and safety valve, as well as pet-cock at the bottom 
for drawing off water which condenses. Our whistle is an ordinary "Siren," 
such as is used on steam vessels and some few factories. It is 45^ inches ir. 
diameter, and the "chimer" is actuated by a drum and weight arrangement. This 
whistle is placed ten feet above the house so as to carry sound over adjacent 
buildings and is connected with the cylinder by inch piping; the chain which 
opens the valve in the whistle, trips at the same time the pall on the drum which 
operates the chimer and thus starts all off together. Our pressure is put on by a 
double action air compressor which is operated by an electric motor. These 
compressors can be had at most any price according to their capacity, from that 
capable of being run by main power — which would take, possibly a whole day to 
charge a tank the size of ours — down to the combination double action com- 
pressor, capable of putting 100 lbs. pressure on it in an hour but requiring five 
horse-power to operate it. Our plant as it is, is a decided success. We carry 
100 lbs. on our cylinder constantly and this will run our whistle about 90 seconds. 
It seems hours. When an alarm comes in, should it be at night, the driver as he 
slides down the pole from the sleeping quarters pulls the whistle chain and puts it 
on a hook and goes on about his business, and the whistle blows until exhausted 
or is released. It can also be used, after giving a long blast to awaken the fire- 
men, to give the number of the box called by short blasts." 



FIRE ALARM WHISTLE. 



A compressed air fire alarm whistle has been invented by F. E. Whitney, 
of Boston, Mass., and is said to be a most satisfactory one. Towns that have 
no available steam for steam alarm whistles will get good results by taking water 
for pumping the air direct from the street mains It is now in use at Arlington, 
N. J., and is being investigated by a large number of fire chiefs who look upon it 
as a simple and economical- method of alarm, in connection with Gamewell or 
other systems. 



I 



USE. 



1089 



THE RUTH PNEUMATIC CAR FURNISHINGS. 

1 The private car of the vice-president of the Pittsburg and Lake Erie Rail- 

iroad is equipped with the Ruth pneumatic mattresses and chair seats. These ap- 

.ances are contained in one compartment of the car, and consist of four sec- 




FIG. 463 — INTERIOR OF SLEEPING CAR. 



ions, or eight single beds, furnished with eight heavy duck and rubber mat- 
resses that can be inflated with air from the engine by simply turning the air- 
ock provided near each bed. 

When not in use, and the compartment is being used as a parlor, they are 
ntirely out of the way and one would not even suspect them of being a part of 



logo USE. 

the furnishings of the car. When not inflated they shut up like an accordion, 
being formed in pleated folds, and fit into the side of the car and are covered 
from sight by the piece forming the side of the beds. 

The partitions dividing the berths are fitted closely to the inside wall of 
the car, the portions of the partition that would cover the car windows being 
cut away. These partitions are fitted with shutter windows sliding vertically, 
and can be opened or closed as desired. If closed, they cannot be opened by the 
occupant of the berth. When opened in either the lower or upper section the 
two sections have free communication, and this arrangement is desirable in case ( 
of sickness or for families with children. The operation for transforming the i 
parlor to a sleeping compartment is simple and easy. The porter by turning 
the same air valve that inflates, siphons the air from the seats of the chairs and > 
then turns their backs down, making them low enough to fit under the bottom . 
berths. ! 



PNEUMATIC HORSE-COLLARS. 

The bicycle craze and the numerous fads of the day have not entirely done 
away with the love for that noblest of animals, the horse, and while its devotees 
are considerably fewer than a few years ago, there are still many who cling to 
the thoroughbred and are constant in their search for inventions which may be of 
use to a horse or conducive toward the lightening of its work. 

An Albany, N. Y., gentleman, touring in Europe not long ago, came across 
a new invention in the shape of a pneumatic horse-collar. It was in Milan, Italy, 
that the Albanian saw the new kind of collar, and, charmed with its qualities, he 
ordered two of them made and sent to his home. 

These collars arrived in Albany a few weeks ago, and were placed on exhi- 
bition at George L. Russell's stable. No. 362 State street, where they were ex- 
amined by a number of well-known lovers of horse-flesh and heartily approved. 
Both collars are pneumatic, and one is finished in black, while the other is in rus- 
set. They are the only collars of the kind in the country. The collars, in appear- 
ance, are similar to the ordinary horse-collar, of superior workmanship, but 
instead of the usual packing of horsehair and straw, there are pneumatic tubes 
which are blown up and made to fit the horse's neck, much the same as the tire 
on a bicycle. The collars are of the finest workmanship, and took the first prize 
offered by the Society for the Prevention of Cruelty to Animals at the exhibition 
held in Milan during 1895. 

The principal features of the collar are its velvet-like surface and extreme 
lightness. No horse wearing this collar will be troubled with galling or chafing, 
for the make-up of the collar prevents both. — Blacksmith and Wheelwright. 



A PNEUMATIC LETTER COPY BOOK. 

A London stationery firm has brought out a novel invention in the shape of 
a letter copy book, which is compressed pneumatically. The device is intended 
principally for travelers, wherever it is impracticable to make use of a press. The 



i 



USE. 1091 

book is similar to an ordinary copying book, in general appearance, but is pro- 
vided with clasps to hold the covers firmly and furnish resistance to internal air 
pressure. Within the book there is a thin inflatable rubber bag connected with an 
air bulb which can be detached. When it is desired to copy a letter the leaves are 
moistened or a damp cloth is applied in the usual way, the book is closed and 
clasped and the air bag is pumped up by means of the bulb. It is said that the 
pressure is even and that good copies are obtained. The book is on sale in the 
London stores. — Railway and Engineering Reviezv, Sept. 23, 1899. 



A PNEUMATIC BELT SHIFTER. 

One of the latest useful applications of compressed air in machine shops 
is reported in the April Locomotive Engineering. 

The device is applied to countershafting, for the purpose of shifting a belt 
from the loose to the tight pulleys, and the reverse. It consists of a small air 
cylinder with a piston travel, such as will give a belt the proper throw; the 
cylinder is piped from each end to a two way cock, the plug of which has a bar 
with a looped cord within reach of the operator. Attached to the piston is an 
arm which extends down to the bar carrying the shifting forks — air does the rest. 



A PNEUMATIC ELEVATOR SAFETY. 

The statement has been made on good authority that the elevators in New 
York City carry more passengers than the surface cars. Whether this is true or 
not, it must be admitted that there are grounds for the claim. In other cities, 
with the exception of perhaps Chicago, we question whether the proportion would 
be more than 25 per cent. In any case, the statement serves as food for thought, 
and suggests a comparison of other features. 

Two fundamental diflferences exist between the two forms of transportation. 
First, the elevator travels in a vertical plane, while the tram moves in a hori- 
zontal plane. Again the tram car, with the exception of the cable road, is always 
independent. The elevator car, from the nature of things, cannot be self-propelling 
and must always depend upon the lifting cables. 

Also, since there is only one car in the case of the elevator it is ordinarily 
possible to stop or start the entire operating apparatus when it is desirable to stop 
or start the car. There are, however, occasions when brakes or some means of 
quickly and surely stopping are of vital importance. 

Generally speaking, the present forms of elevator brake must of necessity 
differ from a tram brake, as they cannot be applied on the up trip without the 
greatest risk and the action on the down trip is mostly a matter of uncertainty. 

In railroad practice the prime requisites of a brake are reliability, absolute 
control on the part of the engineer, and suflficient power for all possible demands. 

It would seem that the same conditions are quite as essential for an elevator 
brake, certainly absolute control on the part of the operation is the only one 



f092 



USE. 




vMEooe 



SUPPLY P/Pf" 
FIG. 464 PNEUMATIC ELEVATOR SAFETY. 



USE. 



1093 



rhich can be questioned. With present forms control by the operator is inad- 
visable and we may say impossible. The only reasons for this statement are that 
the operators may become confused and present clutches, catches and safeties, 
all depend upon springs or wedges which are driven in by the falling of the car, 
and there is no way to adjust these with the necessary nicety that is possible with 
street or tram cars. 

In answer to the first of these objections, it may be stated as a general 
proposition that a given operator would be less rattled with a braking device over 
which he has control, than one over which he has no control. 

Further, if he had the perfect confidence which frequent handling and test- 



Hmke Conlrol 




Valve 



- £lev£it0r 
Starting Lever 



< 







FIG. 465 — ELEVATOR BRAKE. 



ing inspires, the probabilities are that he would be no more confused than the 
engineer of a train or the average motorman. 

The second proposition can only be answered by suggesting some form of 
brake which will admit of an adjustment by the elevator operator. 

A review of the conditions outlined causes one to wonder why the air brake, 
which has proved so satisfactory in the case of horizontal vehicular traffic, has 
not been applied to those moving in a vertical direction. To better illustrate 
this idea, the accompanying sketch has been prepared. It shows an elevator car 
equipped with an air brake and ihistratcs in a general way the principle involved. 

The car is provided with two companion clamp jaws for each guide rail, and 
these jaws may in addition to their function of brakes serve as guides. These 
jaws are ordinarily held apart by some form of spring and thus permit a free 
movement of the car up or down. Centrally placed between the clamps is a 



I094 



USE. 



cylinder with two pistons as shown. In some accessible place, either on top or at 
the bottom of the car, is a steel bottle or reservoir, designed for a pressure of 500 
lbs. pressure. This is connected through a suitable system of piping to the brake 
cylinder, and an engineer's valve placed beside the operator or, if necessary, form- 
ing part of the elevator starting lever. A small gauge just in front of him shows 
the pressure in the reservoir, so that a positive indication is always given of the 
working condition of the system. 

The brake handle, which is always in the hand of the operator, has two 
positions, "Slip" and "Fall," which are indicated by stop notches like those of the 
engineer's brake on a locomotive. The first of these would be used when the 
elevator speed increased more or less gradually, and the second for a sheer fall. 

The safety could be actually and instantly tested once a day or once a week 
by the elevator operator by one movement of the same lever with which he con- 
tinually stops or starts the elevator. This practice would make him so familiar 
with the apparatus that he would not get rattled in case of a fall. Reservoirs 
could be replenished each night from a small compressor in basement, using a 
hose to connect with the tank on the car ; or new cylinders could be slipped into 
place when the pressure gauge indicated an insufficient pressure; or a flexible 
hose could be connected with a compressor in the basement and allowed to trail 
after the car. 

Another plan would be to have a little compressor on the bottom of the car, 
which would be driven by a small hemp rope, running from top to bottom of the 
shaft. 

Probably the best way would be to have closed bottles with air under high 
pressure, say 2,000 lbs., which could be placed on the car once a month or two 
months, or even at longer intervals. A suitable reducing valve would then drop 
the pressure to 500 lbs. or whatever working pressure was decided upon. 

The following abbreviated calculation will show the operation of such a 
system. 

Assume car and passengers to weigh 5,000 lbs. 

In case of accident this must be carried on two clamps, or 2,500 lbs. each. 

Assume coefficient of sliding friction* to be .04, which is conservative for a 
speed of 50 miles per hour. (50 X 5,280 = 214,000 ft. per hour, 3,560 ft. per 
minute or 59.3 ft. per second.) 

Assume brakes applied at the end of a two-second fall, the distance fallen 
would be 

s=}4 gt.^=^i6.2x 2^=64.8 
Therefore the clamping pressure necessary on each jaw to hold the load 
imposed by falling at the rate mentioned would be 

2'5oo , „ 

=62,500 lbs. 

.04 

Allowing a factor of safety of 4 to cover any uncertainty in the character 

of the friction between the clamps and the guide rail we have 

4 X 62.500=250,000 lbs. 
or the amount each pair of jaws must clamp. 



" Kent," page 928. 



w^ 



USE. 1095 



Assume the clamp jaws to have a short arm of 25^2 ins. and a long arm of 

12^2 ins. or a ratio of i to 5 

250,000 

-^ =50,000 lbs. 

or the amount which must be applied at end of the long arm. 

Let the wedge angle equal 10° total, or 5° on each side of the axis, then 
Cos 10° X 50,000 = .98481 X 50,000 = 49,240 lbs. normal. 
49,240 X sin 10° = 49,240 X .1736 = 8,547 lbs., 
which is the thrust the piston must receive to force the wedge between the long 
arms of the clamp levers. 

Assume a working pressure of 100 lbs. per sq. in. 

Q r/ii-7 

-- — —85.47 square inches. 

A circle 10J/2 ins. in diameter has an area 86.59 sq. ins., so the working 
cylinder would require a diameter of 105^ ins. 

With 500 lbs. working pressure the cylinder diameter would be about 
5 7-32 ins. 

If we allow H ill- clearance between jaws and }i in. for lost motion there 
will result ^ in. movement for the short arms of the clamp. 

% X 5 = 1% ins. for the long arm, or we will assume i in. With a wedge 
ratio of 10 to i each piston must move 10 ins., in opposite directions, or a total of 
20 ins. 

85 sq. ins. X 20 = 1,700 cu. ins. or about i cu. ft. per application of the 
safety. 

A tank 9 ins. in diameter and 4 ft. long = 63 X 48 = 3,024 cu. ins. or about 
2 cu. ft. 

At 500 lbs. this tank would be capable of about 10 actual applications of the 
safety, something which would require about as many years, if past experience is 
considered. 

With a pump on the car driven by a rope, as described, with a cylinder 
having an area of i sq. in. and a 4 in. stroke making 40 strokes per minute the 
tank could be filled with air at 100 lbs. pressure in about two hours, or if allowed 
to run continually the safety could be given a working test twice per day and at 
the same time always be ready for emergency. 

J. J. S. 



MACHINE FOR FITTING VEHICLE SPRINGS. 

A novel machine for the fitting of vehicle, locomotive and car springs, also 
other springs of similar construction, has been patented by A. A. Landon, formerly 
with the Kalamazoo Spring and Axle Co., Kalamazoo, Mich. 

This tool is operated by compressed air by means of a hose connection and 
a 3-way valve, and an ingenious arrangement of rollers connected to the end of 
piston rod and on frame of machine. In operation, after the two plates have been 
put together over the "Jack" pin on fitting horse, the machine is engaged by slip- 
ping plates through lower opening of frame and turning to an upright position ; 



1096 



USE. 



the air being turned on, the upper wheels engage the hot plate on top and lower 
wheels the under side of cold plate, in practically the same manner as in hand 
fitting. The crank, or handle, is then revolved, causing the machine to travel over 
every part of the hot plate, causing the hot plate to take in every sweep and curve 
of the cold plate in a more perfect manner than can be done by hand. It has the 
advantage of not necessitating the changing of the spring fitting horse or tem- 
pering tub, but is used in connection with same, it being only necessary to bring 
an air pipe down over the tub. A peculiar feature of the spring business is that it 
is impossible to make a stock of goods ahead, very nearly all orders differing 
in some respects. 

The advantage of this machine over the old style spring fitting machine is 
that it needs no adjustment and is always ready to fit an order of any size, it not 
being necessary to adjust same as with the old style machine, it pinches the two 




FIG. 466 — MACHINE FOR FITTING VEHICLE SPRINGS. 



plates together in the same way as hand fitting, and is adapted to any width of a 
spring. A small order can be fitted in the time necessary to set the old style 
machine and will give a correspondingly better economy on large orders and 
when operated in connection with the main plate bent in bankbending machine 
will make a saving of from 30 to 50 per cent, over hand fitting on vehicle springs 
and should do better than 50 per cent, on locomotive or other heavy springs. It 
is operated by unskilled labor and is adapted to either oil or water temper, and is 
at present in successful operation in one of our largest spring shops. 

This machine marks the introduction of compressed air in the spring 
industry, and we are certain it will lead to the use of compressed air appliances in 
the more progressive concerns of the country. 

Mr. A. A. Landon is at present connected with the American Radiator Co., 
manager of the Titusville Plant, Titusville, Pa., and will gladly give any further 
information that may be desired by interested parties. 



3^-- 



USE. 
ORDE'S LIQUID FUEL BURNER. 



1097 



Mr. Orde, chief engineer to Messrs. Sir W. G. Armstrong, Whitworth & 
Co., of England, have recently introduced an oil burner which is of such design 
as to attract attention. 

This burner, Fig. 467, together with the apparatus shown in Fig. 468, 
has, after considerable attention and expense, been brought to a very high degree 




FIG. 467 — SECTION OF OIL BURNER. 

of perfection, and is now being used on several large steamships. It will be seen 
from the drawings that the system upon which this apparatus works is that of 
heating the oil before it reaches the burner. The air which is used is also pre 
heated, and is carried into the furnace in such a manner that complete combustion 
of the fuel results. From experiments recently made, it appears that about 15 



i^f/^ 




FIG. 468 — ARRANGEMENT FOR BURNING OIL FUEL APPLIED TO BOILERS, 

lbs. of water were evaporated from and at 212 degrees per lb. of oil consumed, 
and that about 16 lbs. of air was used per lb. of oil. 

The analyses of the combustion gases show that a perfect combustion of 
the oil took place, there being no traces found of hydrocarbons. A further point 
is the regulation of the supply of air, which is so perfect that practically no excess 
of air is admitted into the furnace. The table also indicates that no carbonic 
oxide escapes into the chimney. In addition to this, a very important point 



1098 USE. 

brought out in the analysis is that only 3 per cent, of the steam produced was 
used for pulverizing purposes, which is a result which may be regarded as ideal. 
In other methods 12, 15 and even 20 per cent, of the steam produced has been 
utilized for the purpose of vaporizing the oil, and this has to a great extent pre- 
vented the adoption of liquid fuel on steamers. 

Various experiments have been made, and, as a rule, unsuccessfully, to 
substitute air, compressed or otherwise, for steam. 

The burner itself is of the simplest construction, and will, therefore, be very 
easy to manipulate. Although the invention has only recently been completed, it 
has been introduced in the passenger steamer "Saxonia," a passenger vessel trad- 
ing between Hamburg and China. The Hamburg- American Line has also placed 
an order for seven steamers to be fitted with this burner. The steamship "Arista," 
belonging to the Raas Company, has also been fitted. 



MEGAPHONES IN FOG SIGNALING. 



Lighthouse Board Experimenting With New System for Benefit of Mariners. 

The Government Lighthouse Board is making experiments with a new 
system of fog signaling at Falkner's Island, in the Sound, near the Thimble 
Islands, beyond New Haven, Conn. 

The principle of the new invention was tested last year and found cor- 
rect, and this year the complete apparatus has been put up. It consists of eight 
megaphones, ten feet long, each directed to a different point of the compass. 
The small ends of these eight megaphones meet in a ring, inside which is a 
revolving cowl, which turns on the top of a siren. The siren is kept constantly 
spinning at the rate of two thousand revolutions a minute, and when com- 
pressed air is admitted to it it gives forth a very penetrating and far-reaching 
sound about C in the middle octave. 

Compressed air is supplied to a large reservoir by an oil engine which 
runs at high speed. From this reservoir the air is taken to the siren through 
an oddly constructed valve by means of which a current of air at a pressure of 
two hundred pounds, passing through a two-inch pipe, can be controlled by a 
touch of the finger. This valve is operated by a series of teeth on a signal 
wheel, which revolves slowly, producing different signals as each of the different 
magaphones comes into range of the revolving cowl. 

These signals consist of long and short blasts, the long ones being three 
seconds each and the short ones one second each. The eight points of the com- 
pass are distinguished by the difference in these signals. Opposite points have 
exactly opposite signals, that for north, for instance,, being one long blast and 
for south one short blast. For east it is one long and one short, and for west 
one short and one long. For southeast it is one long and two short, and for 
northwest two short and one long. For southwest it is two short, and for north- 
east two long. 



J 



USE. 1099 

These signals announce to the mariner the direction from which the 
sound comes, so that if a vessel was passing Falkner's Island and heard two 
short blasts it would know that Falkner's Island must be southwest of it. It 
could not hear any other signal but the one pointed toward it, because the mega- 
phones send the other sounds in a different direction; but if the vessel were to 
keep on its course until Falkner's bore due west it would then be unable to hear 
any signal but the short and long blast which signifies west. , 

These signals were suggested by Col. D. P. Heap, engineer of the Third 
Lighthouse District, at Tompkinsville. The principle of the invention, which 
consists in sending sounds in a certain direction to the exclusion of other 
directions and the apparatus by which the signals are worked are the invention 
of R. F. Foster, of New York. — New York Herald. 



THE SARGENT GAS ENGINE OILER. 

The proper lubrication of the cylinder and piston of a gas or oil engine in 
which the average temperature during inflammation is not far from 2,000 deg. 
Fahrenheit, is one of the essential conditions of successful operation. 

In order to obtain the best results, a constant feed commensurate with the 
piston speed is absolutely necessary, as too much oil will cause smoke and too 
little a cutting of the cylinder or piston. 

Then, with a variable speed, as in automobile engines, the amount of oil 
should be in proportion to the revolutions and should stop when the engine stops, 
and to attain such results the feed must depend on some factor of the speed 
such as the induction strokes of the engine. 

Fig. 469 illustrates an oiler which has many excellent features. This oiler 
was designed especially for lubricating the cylinders of gas or oil engines, vacuum 
pumps or air compressors in which the pressure during the induction stroke 
is slightly below atmospheric pressure, which is always true of such machines, 
for if the pressure within were not less than without, the cylinders would never 
fill. The essential features are a glass reservoir which is filled through a hole 
in the top normally covered by the slide A.; B., a needle valve which adjusts the 
feed into the air-tight bullseye, as shown; and D., a check valve held to its seat 
by a spring, the compression of which is adjusted by the nut C, which can be 
turned with a screwdriver. 

While this is essentially a cylinder-oiler, by removing all compression 
from the spring, it may be used in place of the ordinary sight feed oiler on any 
other part of the engine. 

When this oiler is used for admitting oil to the cylinder of a gas engine 
or air compressor, the check valve spring is so adjusted that the valve seats when 
the air pressure above and below the check is the same, but if the air pressure 
below the check valve is rarefied or slightly reduced, the check will open and 
allow the air in the bullseye enclosure to pass into the cylinder, whereupon the 
atmospheric pressure on the oil in the reservoir will force it down through the 



I loo 



USE. 



needle valve to the bullseye chamber, from which it will pass into the cylinder 
every time the check valve opens. 

When the engine stops, rarefaction in the cylinder ceases, the check valve 
remains seated and the oil stops feeding through the needle valve, because oil 
cannot drop into the bullseye chamber if air and oil are not drawn out. 

When compression begins in the cylinder, the check valve shuts and no 




FIG. 469 — GAS ENGINE OILER. 



smoke or pressure from the explosion passes into the bullseye chamber or 
reservoir. 

The reservoir can be filled while the engine is stopped or running with- 
out opening or closing a valve or changing the adjustment of feed. 



USE. HOT 

The quantity of oil is always in sight; the amount feeding can always be 
seen; the oiler stops with the engine and begins when the engine is started 
again, and as no pressure accumulates in the glass reservoir, there is no danger 
of the oil cup exploding. 

This oiler is the invention of Mr, C. E. Sargent, and is manufactured in 
several sizes by Ihe Michigan Lubricator Co., 266 Beaubien Street, Detroit, 
Michigan. 



AIR SURFACE CONDENSER. 



A very interesting pamphlet has recently been issued by Mr. Fred Fouche, 
of Paris, who exhibited an apparatus showing a new method of condensation 




FIG. 470 — AIR SURFACE CONDENSER. 



for creating a vacuum in the exhaiist of steam engines, the condensation being 
practically on the same principles as is now, and has been, effected in surface 
condensers, with the exception that instead of using cold water for condensa- 
tion purposes cold air takes the place of same. 

Mr. Fouche had one of these installations at constant work at the Paris 
Exposition, and claims that his apparatus would be of great value if adopted 
in places where fuel is expensive, where water for condensation cannot be 



iro2 



USE. 



obtained, or in case condensation water would contain lime or other foreign 
material which would be detrimental to the effectiveness of a surface condenser. 

The apparatus which Mr. Fouche is placing on the market consists of a 
surface condenser consisting of narrow exhaust steam spaces between corrugated 
iron or steel plates, having a great condensation surface, instead of tubes, as 
generall}'- used in surface condensers. He claims that by adapting this method 
he can obtain a greater condensing surface with a lighter weight and lesser cost. 

In addition to the above apparatus, a motor, or engine, and a fan are 
required to transmit a current of cold air between the different sections of cor- 
rugated plates containing the exhaust steam of the engine, or engines, this 
current of air to be sufficient for condensing the exhaust steam from the main 
engine. 

From tests made by the inventor, he does not claim to obtain as high an 
efficiency as that of surface or jet condensers, but he claims to come to within 
3 to 5 per cent, of the actual efficiency now obtained by the above, and maintains 
that such a new deparature in the line of condensers for stationary engines or 
locomotives should be seriously looked into by investors, who desire economy and 
dividends accruing therefrom. 

It is a well-known fact that a locomotive consumes from 5 to 7^ lbs. of 
combustible per horse power per hour, and if a condenser could be adapted to 
same and create a vacuum of only 20 inches per sq. in., a benefit of saving in 
fuel and water consumption, varying from 15 to 25 per cent., would be effected. 

Taking the above data into consideration, Mr. Fouche makes the state- 
ment that the weight of an air surface condenser, with its fan and engine, will 
equal about the weight of water and coal saved in a two hours' fun of an 
ordinary passenger train running at a speed of 40 miles an hour, and, in addition 
to that, make a saving of an average of 20 per cent, of the amount of coal used 
for the engine. 

Taking as a basis that a locomotive develops on an average only 500 H. P., 
which is low, as the Empire Express develops at times as much as 1,400 H. P., 
and rating the coal consumption at six pounds per horse power per hour, we 
figure that a saving of 600 pounds of coal per hour could be effected, not count- 
ing the saving in water consumption. 

The reader will understand, of course, that for adaptation on railroads, 
the condensing apparatus would have to be placed on a special auxiliary tender. 

This matter, we think, should be of interest to any railroad company, as 
the question of fuel is so important at the present time that it cannot be over- 
looked. 

The inventor, in his pamphlet, omits to mention the weight of the con- 
denser to suit a certain horse power, nor does he give the number of sq. ft. of 
cooling surface he would suggest per pound of exhaust steam at atmospheric 
pressure. 

Should any reader be interested in the subject, we will be pleased to 
obtain any information we can in the matter. 



USE. 
SHEEP SHEARING IN AUSTRALIA. 



1 103 



Many attempts to perfect a mechanical device which would lighten the 
work for the shearer, prevent the wool from being injured by second cuts and 




SHEEP SHEARING IN AUSTRALIA 



FIG. 471 — SllEAKINCi SHEEl' BY COMPRESSED AIR. 



guarantee the neat fleece to be even in length, or "wool topped" have in the i)ast 
twenty years been made. 

A machine such as we illustrate was invented, and is simple and easy to 
handle. The simplicity of the construction dispenses with the necessity of skilled 
labor in setting up, adjusting or running the machine. 

The use of this machine reduces the time of shearing from an average of 
70 sheep by hand to about 100 per day of ten hours, or in other words one ma- 



II04 



USE. 



chine can accomplish in one day as much work as it formerly required three 
men to turn out. 

Another point in favor of this invention is that by its use the animals are 
never mutilated, and the wool brings a better price in the market, on account of 
the length of its fibres. 

In Australia, the foremost country for sheep raising in the World, this ma- 
chine has been introduced and is being used on a large scale with most satisfac- 
tory results. 



COMPRESSED AIR DRY DOCK. 

We illustrate herewith a dry dock, the invention of August Geiger, engi- 
neer, of Portland, Oregon, operated by compressed air. The dry dock is of the 
floating type, but unlike ordinary floating dry docks, it has no bottom, so that 
the water can flow in and out with perfect freedom. This dry dock has no pump- 




FIG. 472 — DRY DOCK. 



ing machinery ; in its place an air compressor is used. The compressor is located 
upon an elevated platform, running parallel with the long sides of the dock, and 
is connected by pipes to the different water-tight compartments into which the 
dry dock is divided. 

In order to lower the dock, valves near the compressor are opened, air 
rushes out, and water flows in from underneath, causing the dock to sink. When 
the dock is to be raised, the compressor is started up, air is forced into the com- 
partments, the water is driven out and the dock rises to the surface. 

Suppose a vessel of 25 ft. draught (about the greatest draught steamers 
have) was to be docked. It would be necessary to sink the dock about 28 ft., and 
in order to raise it, air pressure of about 14 pounds to the square inch would be 
required. The higher the dock is raised, the less pressure is needed. 

Assuming a dock of 300 ft. length, 80 ft. width and 7 ft. depth, we have a 
large box of 300 x 80 x 7 ft., = 168,000 c. ft. This amount of compressed air 
is necessary when the dock is out of the water, but as the water displaced has only 
7 ft. depth, = 84 in., the pressure required is only 84 in. -^- 28 = 3 lbs. per square 
inch. As the lifting capacity of a dock is equal to the weight of displaced water, 
it would be in this case, if in a river, 168,000 c. ft. x 62 lbs., = 10,416,000 lbs., = 
S,2o8 tons, less the weight of the dock itself. 



USE. 



1 105 



One great advantage of such a dock would be the bottomless construction 
hich in a dry dock of 300 x 80 ft. means a saving of 24,000 sq. ft. of water-tight 
flooring ^nd caulking, which is quite an item; and with this system, a cheaper 

Iock can be built than with the old-style pumping machinery. 
Another point in favor of this style of dry dock is, that the lifting power 
cts under the upper side of the big box, which makes it steadier and less liable 
5 topple over than with the ordinary dry dock, where the lifting power acts under 
be under side of the big box. 
■ ! A r 



PNEUMATIC DOCK. 



OLD STYLE. 



A A A A 

FIG. 473 — OLD AND NEW METHOD OF APPLYING LIFTING POWER. 

Mr. Geiger thinks that compressed air could be more quickly furnished to 
raise the docks than it would be possible to pump water out by the old system. 
The pipe connection would be smaller, and in general less machinery would be 
required. 



NEW CANAL LOCKS. 

A pneumatic canal lock, designed for use in the Erie Canal at Lockport, 
N. Y., is attracting attention of canal builders and engineers. By its introduction 
the greatest simplicity will be obtained and many of the difficulties experienced 
in operating locks will be obviated. It is estimated that one pneumatic lock will 
take the place of the sixteen locks now used at Cohoes. 

The principle upon which the Button Lock works is described in the New 
York Sun in this way : 

*Tf you were to take two tumblers and fasten them together, bottom to 
bottom, you would have the equivalent of one section of the new lock. Partly 
fill the upper tumbler with water and put them both in a tank of water, with the 
open mouth of the lower tumbler don'nward. With a straw blow the air into the 
lower tumbler until it rises almost clear of the water. Now take another pair of 
tumblers and arrange them in the same way beside the others. Put a U-shaped 
tube under the two tumblers, connecting the air spaces of each. Balanced upon 
the compressed air, both sets of tumblers would rise or fall in unison. If you 
depress one, the other will rise." 

The inventor, Mr. Dutton, has developed a wide range of ingenuity in the 
devices used in the construction of the new lock. When it was first proposed to 
use air to operate the lock, the size of the pipes and the valves which would be 
required were looked upon as a settling argument against the method. Nobody 



iio6 USE. 



thought of making a valve to fit a ten-foot pipe. Mr. Button got around the 
trouble by using for a water seal a U-shaped pipe such as is used for cutting 
off sewer gas in house plumbing. A 4-inch water cock controls this, and en- 
ables a lo-foot pipe to be opened or closed to the air almost as quickly as if a big 
metal valve were used. 



AIR AS A LUBRICANT. 

Ordinary air is now being used with good results for illustrating the action 
of a lubricant in a journal bearing in a machine designed by A. Kingsbury. The 
machine consists of a steel piston or short shaft to be rotated and a cast-iron 
ring or cylinder which acts as a bearing for the shaft, the whole being supported 
on rollers mounted on a suitable frame. The shaft weighs 50^ pounds, is 634 
inches long and 6 inches in diameter, and its weight constitutes the total down- 
ward pressure on the bearing. The diameter of the cylinder is slightly less than 
1-2000 of an inch larger than the shaft— a fairly loose fit. Both cylinder and 
shaft are ground exactly parallel. 

The cylinder is set horizontally, the shaft inserted (both being perfectly 
clean and dry) and rotated with the band by the handle at the end. It can be 
turned with difficulty at first, and the harsh, grating sound of metal rubbing on 
metal will be heard. With an increase of speed, however, this grating ceases, and 
the force required to turn the shaft is materially decreased until, after a few 
revolutions, the shaft becomes entirely free from the cylinder and rotates on the 
film of air between. Set rotating at, say 500 revolutions per minute, it will con- 
tinue to rotate four or five minutes. If allowed to run, the speed gradually de- 
creases from the start until suddenly the piston breaks through the intervening 
layer of air, and a few more revolutions suffice to bring it to a sudden stop. 

If a more conclusive proof is required that the shaft is entirely separated 
from the cylinder, an electric bell may be included in a circuit of which the shaft 
is made one terminal and the cylinder the other, when it will be found that the bell 
is silent as long as the shaft rotates at any considerable speed. 



AN ACCOUNT OF THE ATTEMPTS TO INTRODUCE COMPRESSED 
AIR FOR STEERING VESSELS. 

The first application of compressed air for steering vessels was made about 
fifteen years ago; by permission of the Government, on the U. S. Steamship 
"Tallapoosa," an old vessel which was sent to the South American coast. As a 
system it proved satisfactory, according to the reports officially made to the 
Bureau of Navigation, but some mechanical defects were needed to be remedied 
which could not be done at that distance. The vessel was afterwards con- 
demned and sold. The principle of compressed air for steering was fully 
endorsed, and the cost of the test was allowed to the interested parties. The next 
application was made on the old Dominion S. S. "Seneca," and the reports of it^ 



USE. 1 107 

captain were very satisfactory. I quote from the reports of Capt. Geo. M. Walker, 
1887: 

"After using it for six months during which time it cost nothing for 
repairs, giving the most complete and perfect confidence in controlling the ship in 
storm and fogs, dark nights and through fleets of vessels. It must when prop- 
erly known come into general use." It was used for two years with gratifying 
results. The gear on the S. S. "Seneca" afterwards became the property of the 
Pneumatic Steering Gear and Mfg. Co., of New York, who obtained control of 
the patents. 

While trying to improve some mechanical defects, it was ordered off the 
vessel as it was ascertained by the influence of a steam steering company who 
afterwards put their own steering gear on board. 

The reports to the Government made in 1887 recommended the system to 
the favorable consideration of the Navy Department, by the members of the 
Pneumatic Gun Carriage Co., of Washington, D, C. In the meanwhile the Pneu- 
matic Steering Gear Co. allowed experiments to be made, mechanically different, 
for the Staten Island Ferry Boat, which proved to be worthless. After spending 
considerable money on the experiment, that gear with the one taken from the 
"Seneca" was sent to the Morgan Iron Works of New York for the purpose of 
being made mechanically useful, and as far as possible perfect, but owing to lack 
of means at the time to carry out their purpose, the Company have virtually done 
nothing since. Later permission was given to the Pneumatic Gun Carriage Co., 
of Washington, D. C, to use their devices, the company having made a contract 
with the Government for the entire system, on the U S. monitor "Terror." Both 
companies are now waiting for a full endorsement of the system with order for 
olher vessels, for which recommendations have been made and resolutions offered 
ir. Congress. 

The benefits of the system are: A firmer and greater impression on the 
valves forming a cushion to the rudder head. It also ventilates the entire ship. 
It is noiseless and does away with odors and hot steam pipes, and the danger 
from their bursting. There is no possibility of freezing from condensation, and 
the exhaust reduces the temperature. Engineer T. W. Kinkaid, of the U. S. 
Navy, in an article in the Journal of the American Society of Naval Engineers 
(Vol. IV., No. i), says: The pneumatic system is simple and powerful and pos- 
sesses advantages over the hydraulic and electric systems. There is no burning 
out of fuses, as with electricity, and no danger from burns or electric shocks, nor 
from drenching, as with the hydraulic system. There is no increase of tem- 
perature, and the exhaust improves Ihe ventilation, all of which things are advan- 
tages over steam and hydraulic and electric systems. 

On the trial trip of the monitor "Terror," the rudder was turned from 
hard-a-port to hard-a-starboard in six (6) seconds 68 degrees. The area of the 
rudder is eighty-two sq. feet, the pressure of 125 lbs. per sq. inch is maintained 
by one air compressor. A pressure was maintained not below 30 lbs. and not 
nbovc 60 lbs. for steering. 

Air leakage has been entirely overcome by a process which has been tried 
successfully by the Cramps, of Philadelphia, Pa. 



iio8 USE. 

The final report further says that the system is quick and accurate, and the 
engine does not get out of order, and the engine room is free from noise, dust, 
heat, moisture and shock. 

The system has been endorsed by Commodore G. W. Melville, Engineer- 
in-Chief, U. S. N. The Naval Board endorses it as being superior to all others, 
using the word excellent. Rear-Admiral Mathews endorses it, and Chief Con- 
structor Hickborn reiterates all that has been said and recommends it. 

Interested parties, with the experience of the past few years, are preparing 
for further superiority in the use of compressed air for steering vessels in the 
formation of a new company, controlling all improvements for the purpose. 

The system is attracting much attention in England. 

Jos. C. Walcott, President, 
Pneumatic Steering Gear and Mfg. Co. 



Editor Compressed Air: 

A copy of your monthly publication has been given me lately; being 
interested in pneumatic appliances, but more especially in its use for steering 
vessels. It has been tried and approved of for ten years past, but has not come 
into universal recognition for this purpose yet. While formerly tried on a U. S. 
vessel and a coast steamer with success, its last application is in the U. S. monitor 
Terror, which did some good work during the late war, and proved effective, with 
many other uses to which it was put on board, but more especially in its use for 
steering. The slow progress in its adoption has come from other systems more 
strongly backed, and owing to too much red tape at Washington. Senator Chand- 
ler, on Dec. 6th, 1898, brought the subject forward in a resolution, asking why 
the pneumatic system is so overlooked, when it has proved so effective. It is 
gaining ground every day for everything, here and abroad. 

The ScientiHc American of March 20th, 1897, and March 7th, 1898, has an 
article on the pneumatic system on the U. S. monitor Terror, with illustrations. 
To corroborate what I write, I can refer you to many reports of the Navy De- 
partment and others, endorsing the system for the Navy. 

The elevated road has talked of using compressed air, but there is a pres- 
sure to have electricity adopted. 

I have been much interested in Mr. R. P. Whitelaw's article you publish. 

Joseph C. Walcott. 
Stamford, Conn., Feb. 20th, 1899. 



CLEANING CAR CUSHIONS BY COMPRESSED AIR. 

The illustration on page 1109, Fig. 474, represents another useful appli- 
cation of compressed air. The picture was taken at the Pullman platform in the 
N. J. Central yards in Jersey City, N. J. Cushions, carpets, bedding, curtains 
and rugs are taken from the cars and arranged conveniently on a platform, the 
operator takes the hose with its spray nozzle and holds it directly over the article 
to be cleaned, air is turned on and the accumulations of dust of one trip is in- 



USE. 



1109 




FlC. 474 — CLEANING CAR SEATS WITH AIR. 

stantly dissipated. It takes less than a minute to thoroughly cleanse a car 
cushion. Besides removing the dirt, the upholstery is purified by the vigorous 
airing it has received. The hose is taken inside the car and the stationary up- 
holstery and hangings are renovated. 

Few dwellings receive the refreshing application of air that these cars 
receive. In no other way can healthfulness and purity of atmosphere be as- 
sured in railway carriages. Its use should be extended to every railroad. 



CARS DUMPED BY AIR. 



The Thacher Compressed Air Dumping Car is being placed on the market 
by the Thacher Car and Construction Co., New York. It is claimed that with 
this car much time is saved, and that loads can be discharged by trainmen of the 
construction train, the engineer operating it from the engine, and the ordinary 
air pump supplying the air. 



mo USE. 

The mode of operation of the dumping device is as follows : 

The body of the car being pivoted centrally will dump to either side, or to 
one side only, according to its construction. 

This is done by means of a cylinder mounted on the truck frame, the pis- 
ton of which is coupled directly to the car body; another smaller cylinder called 
the "latch cylinder," fitted with piston rod and slide valve, positively and auto- 
matically operates the latches which lock the car body in its horizontal or normal 
position, and also regulates the distribution of the air to the large or dumping 
cylinder as required, moving its piston up and down, thus dumping the body and 
returning it again to its horizontal position. 

An independent reservoir which each car carries contains an ample supply 
of air for the purpose of supplying the movements of the dumping cylinder, and 
is filled and kept at the necessary pressure by the engineer at any convenient 




FIG. 475 — PNEUMATIC DUMPING CARS. 

time, a check valve preventing its escape until needed. This reservoir is filled by 
the regular train pipe, which is also utilized as the air brake pipe and does not 
interfere with the latter's action. 



A LOCOMOTIVE FIRE KINDLER. 

The Ferguson locomotive fire kindler, which is being introduced to the 
market by Leach & Simpson, Old Colony Building, Chicago, and which is illus- 
trated herewith, consists essentially of a tank to contain oil, a hose coupling for 
connection with the compressed air system or with the main reservoir of the 
engine, a hose terminating in a nozzle for spraying the mingled oil and air and a 
valve for controlling the relative proportions of oil and air. The tank is most 
conveniently mounted on a truck, by which it may be easily removed from one 
part of the roundhouse to another. 



USE. nil 

The valve is the principal feature of novelty. Turning the cock regulates 
the proportions of air and oil admitted into the tube. Turned one way, air alone 
passes through and oil adhering to the inside of the hose is removed. 

The tank holds twenty-five gallons. This is sufficient to kindle fires in 
forty engines, on an average. The time required is about forty-five minutes with 
a cold engine and perhaps twenty-five minutes when the engine is still warm — 
more or less, according to the temperature. This means getting up sufficient 
heat to remove the engine under its own steam. 

The portability of this kindler and the intense heat generated by its flame 
make it very convenient to operate. When the connections are made a handful 
of oily waste is lighted and thrown into the ashpan to start the flame. The nozzle, 
which is at the end of a long tube, is thrust into the ashpan and the flame 
passes up through the fuel until the latter is wholly ignited. The fire door, 
being kept closed, prevents the admission of cold air and causes the draft to pass 
up through the fuel. This is claimed to be a decided improvement over the old 
method of blowing through the fire door with the jet of flame striking the firebox 
sheets. By the use of this burner it is said that less injury is done to the inner 
sheets than is done by a wood fire for kindling. 

The same apparatus is also used as a blow pipe for heating tires, straighten- 
ing frames, or any other bent work that may require removal and which ordinarily 
has to be sent to the smith shop to be straightened up. For such purposes tho 
heat may be applied to the exact points required without affecting adjacent parts 

An important point claimed for the Ferguson locomotive fire kindler is the 
fact that its use does not require the presence of a compressed air plant. If engi- 
neers are instructed to leave their engines with a supply of air in the main reser- 
voir, the kindler may be attached directly to it, and the fire rekindled by the use of 
air from this source alone. The apparatus may therefore be used at the most 
unimportant roundhouse with the same satisfactory results as at the plant which 
possesses the most complete air equipment. 



TOOLS FOR STONE WORKING. 

The pneumatic tool used in stone cutting is one of great importance, and 
is likely to take precedence of every other device in shaping natural stone into 
whatever forms the architect or designer may specify. The skilled operator of 
this tool will do more work in a given time than ten ordinary cutters could in the 
old way. Its general use will bring about a larger demand for ornamental stone 
work in building and more monuments of better grade will be erected. The 
increased consumption will compensate for the reduction of the force of stone 
cutters, inasmuch as the output will need to be greater and the manufacture of 
the tools will employ large numbers of men. Such labor saving devices are not 
always the means of robbing the mechanic or artisan of employment, but rather 
broadens the field and increases their usefulness. The natural result is then that 



III2 USE. 

a less number of men are not employed, but simply the transposition of talents 
from one activity to another, and mankind in general is the beneficiary. 

Compressed air is the power utilized to operate this tool, and in skilled 
hands it marks out lines of beauty and symmetrical figures equal in finish to the 
clear cut work of the master in the art of chiselry. 

With it the noblest conceptions of the sculptor are quickly wrought into 
enduring form. 

Where power is available the cost of plants may easily be borne by even 
smaller yard owners. 



STONE-CUTTING BY AIR TOOLS. 

Perhaps the most marked improvement in the stonecutter's art since the 
stone age has been the introduction of the use of compressed air. For centuries 
the hard, unyielding stone had been fashioned into shape by the ceaseless efforts 
of the hammer and chisel ; and while other trades adopted newer and cheaper 
methods of manufacture in rapid succession, no means could be devised to hasten 
the tedious processes of stonecutting. 

The arm of the carver could only deliver a comparatively small number of 
blows per minute, but by the use of pneumatic carving tools this number was 
multiplied to such an extent that the blows following each other in rapid succes- 
sion are in effect one continuous blow. 

As the cutting power is always ready, the carver had merely to guide the 
machine and chisel. He can thus give his whole attention to his work, and the 
result is shown in the increased amount of work accomplished, and the work is 
done much better. 

These tools were crude at first, being complicated and liable to injury, and 
the continual breakdowns were a constant source of annoyance. They have "been 
greatly improved and simplified until the latest and best types are but very simple 
in their make up, i. e., the cylinder or case, and plug for same, and the hammer 
or piston that delivers approximately 20,000 blows per minute on the chisel. The 
first tools introduced were operated at 15 to 20 pounds air pressure, as a higher 
pressure caused them to vibrate or "kick" to such an extent that the operator 
could not hold them. Now, however, 80 pounds pressure is easily handled, as the 
disagreeable "kick" has been overcome by the introduction of an air cushion which 
stops the hammer from striking the cylinder head on the up stroke. The machines 
do not run continuously as formerly, and now only use air while actually em- 
ployed in cutting, and automatically stop the instant the chisel is removed from 
the stone. Soon after hand tools became widely used, a need was felt for a ma- 
chine to surface granite, and a large and powerful pneumatic tool m.ounted on a 
radial arm, which is in turn supported on a vertical column or post, met the needs 
of the cutter. These powerful machines eat away granite at an astonishing rate, 
and have no difficulty in surfacing 60 or more square feet per day. 

With the introduction of compressed air into the stone-cutting establish- 
ment, other uses were soon found for such a tractable servant, and now com- 
pressed air operates the overhead traveling cranes and hoists, pumps, sand and 



USE. 



1113 



water for gang saws, blows the blacksmith's fires, and operates the quarryman's 
rock drills, gadders, channelers, etc. 

No doubt in the future still other uses will be found for compressed air, 
and any one putting in an air plant would be wise in making ample provision for 
future needs. 



GRANITE SURFACING MACHINE. 

Fig. 476 shows a granite surfacer which is being adopted in quarries 
and by bridge builders and for general construction where compressed air is used. 




FK;. 476 — GRANITE SURFACING MACHINE, 



It will be seen that an ordinary 2^" rock drill is mounted on a swinging frame. 
It is operated by one man, who begins his work on the undressed block of granite 
at the highest parts of the uneven surface. The stroke is regulated by the feed 
screw as in ordinary drilling, and as the surfacer is being swung around over its 
work it may be regulated by the throttle so as to avoid striking low places, thus 
evening up the surface as desired. The machine shown is now used by the 
Pochuck Granite Co., B. J. Mallon, superintendent, Goshen, N. Y., and has made 
an excellent record. One machine will surface as much as ten men. A test 
showed that in 25 minutes it would do as much surfacing as a good stonecutter 
could do in ten hours. 

The exhaust air can be used for keeping the dust away from the work, and 
this makes it much pleasanter for the operator. 



1II4 



USE. 
CARVING AND DRESSING STONE. 



Fig. 477, given below, is an excellent picture of the interior of a stone man- 
ufacturing plant that is operated by compressed air. The view was taken in the 
shop of L. L. Manning & Son, of Plainfield, N. J., and it illustrates what is being 
done in this important line by pneumatic tools and other improved apparatus. For 







I'^IM 




-w 




■ift;*«*^. 


k^m 


■fl 




^ '1 


ipsri^ 


E^ 


M 






^: 


ij^fc^*,^ J 






M 1 



FIG. 477 — AIR POWER IN GRANITE CARVING. 



dressing and carving granite, marble or other material used as monuments and 
grave decorations, there is nothing so effective for the purpose, and experience 
proves that it reduces the cost of producing handsome designs so that the purchase 
of suitable gravestones is within the reach of all. 

The plant of Manning & Son consist of one vertical boiler and Baxter 
engine, a 6-in. x 6-in. Class "E" Ingersoll-Sergeant Compressor, one polishing 
machine, and a set of pneumatic tools of the Keller pattern. The whole outfit 
was supplied by the C. H. Haeseler Co., of Philadelphia, Pa. The arrangement of 



USE. 1115 

the plant was planned by the owners, and for economy of space, convenience, 
and in general appearance, it appears to be admirable. 

The compressor is run by belt. It takes 60 pounds of steam to run the 
entire plant, and about 40 pounds of air pressure to run the pneumatic tools on 
heavy work. 

With the polishing machine, a piece of granite, 6 ft. x 6 ft., can be dressed 
and polished in two and one-half days. By hand it is said that it would take at 
least one month to do it. 

One pneumatic tool in the hands of a competent operator will do as much 
as three men, and do it much better. It can trace and cut letters, and do all sorts 
of fancy work. A stone-worker having such a plant as the one described has every 
chance of success, and can certainly distance competitors in time and cost. 



EXPERIENCES WITH COMPRESSED AIR IN SHIPBUILDING AND 

SHIP-YARD WORK.* 

Of late years great advances have been made in the use of compressed air 
as a motive power for small tools, and it is already considered on an equality, and 
for many operations, superior to steam, electricity or hydraulic power. 

Practically all the large railroad and ship-building plants in the country 
have adopted this form of power in a greater or less degree. It is possible to 
convey it from point to point with great facility and practically no drop in the 
pressure, though the pipes may be very long. For example, at the Jeddo Tunnel, 
in Pennsylvania, air at 60 lbs. pressure was carried 10,860 feet, and the gauges at 
both ends of the pipe showed no difference in pressure. There are many other 
instances of this kind, where it would be practically impossible to convey steam, 
and consequently a small boiler with fireman would be necessary at the scene of 
operations. Other advantages are that it lends itself for use in all kinds of holes 
and corners. There is very little, if any danger from frost, if the pipes are prop- 
erly laid, protected and drained. There is no chance of short circuits or unfore- 
seen shocks ; no solenoids or delicate armatures to get out of order and no heavy 
mass of iron and copper to transport in the shape of an electric motor, for the 
purpose for instance, of drilling a 54-in- hole. There are no leaky joints as in 
hydraulic motors, and no trouble from condensation and lack of positive move- 
ment as in steam. 

Its economy is equal, if not superior, to any of the existing prime movers, 
if used with judgment and due regard for its capabilities and for the right tools; 
that is, for those various small tools that are located at a considerable distance 
from the source of power, operating in many different places in a short interval 
of time. 

It is the general opinion that air, water and steam are pre-eminently suited 
for pressure operations or where blows are to be delivered, and electricity for 
rotary motion. Experience, however, has taught that for hand tools, both rotary 



* Marine Engineering. 



iii6 



USE. 



and reciprocating, the air engine has most advantages in establishments where 
light and easily handled tools are a necessity. 

The fact that an ordinary mechanic can repair and adjust air motors, while 
it requires an expert electrician to repair an electric motor, would seem to make 
it preferable to use the former method, as ordinary mechanics are more numerous 
in a shipyard than expert electricians. 

Compressed air should be used and not abused. Small leaks are very 
prevalent in the piping, valves and loose couplings, and worn out motors often 
consume an excessive quantity of air. These are very small matters in themselves, 
but taken collectively in a large plant, have a very depressing effect upon the 
coal pile and an elevating one on the expense account. Treat the air plant with 




FIG. 478 — PNEUMATIC DRILL, IN SHIP-YARD WORK. 



the same care that is manifested in the insulation of electric wires or lagging of 
steam pipes and there will be less grumbling heard concerning the wastefulness of 
the system. A committee of the Master Mechanics of the principal railroads of 
this country reported at the last meeting, 1897, that the use of compressed air, 
with suitable apparatus, gave an average economy of from 25 to 50 per cent. 
over the ordinary former practice, in their shops, on the following work: 

Tapping out stay bolt holes, reaming and drilling holes, chipping and caulk- 
ing, removing tires, beading flues, air hoists, vertical and horizontal car jacks, 
tinware presses, shears erected outside shop for shearing off test coupons, tank 
riveters, shears at scrap pile, shears for light sheet iron work, small Pelton wheels 
for operating emery wheels, blast for blacksmith forges, applied to mixing paint 
in large quantities by putting a pipe in bottom of mixing barrel, used in all kinds 
of motors for boring cylinders and facing valves, cleaning cushions inside and out 



USE. 



IIT7 



of cars, blowing out cylinders before inserting packing, rolling flues, swedging 
flues, testing brakes and numberless other minor purposes. 

The following particulars were given of a shop turning out sixty engines 
per year, viz : One compressor with 15-in. steam, 14-in. air cylinders and i8-in, 
common stroke, five elevators, one hoist for driving wheel lathe, six hoists for 
lathes and planers, two Brotherhood engines, three motors, one sand elevator, 
one fire kindler and one flue cleaner. The cost of this compressor, including 
foundations and pipe connections, was $1,260.50. Pipe lines, hose, valves, reser- 
voirs, motors, hoists, elevators, cost $1,189.50. A total of $2,450. 

On a test run of eight hours it required 313 lbs. of coal per hour or 2,508 
lbs. for the run. Pressure was raised from zero to 120 lbs. in 5 minutes, 40 



1 / 
IV 




> 




^' X 




' * ** 


'^ ill i 

1 II J 

1 " ># 











FIG. 479 — PNEUMATIC PORTABLE RIVETER, IN SHIP- YARD WORK. 



seconds. The compressor made 858 revolutions and compressed 2,681.6 cu. ft. of 
free air to 193.9 cu. ft. of air at 120 lbs. It required with this compressor 20.4 lbs. 
coal to compress 1,000 cu. ft. of free air to 120 lbs., equaling 60 per cent, of its 
theoretical capacity. The packing of this engine had not been overhauled for 
eighteen months, thus accounting for some of the deficiency. 

It is during the building of a ship that the advantage of these power tools 
are best exemplified. A hull is full of odd corners and nearly inaccessible nooks 
that must be as well riveted and caulked as the most accessible part of the vessel ; 
perhaps better as it is more difficult to overhaul and examine these places. 

It is not so long ago that the best yards in the country depended upon the 
racket drill and hand riveting, the work having to be done in such inconvenient 
places and uncomfortable attitudes upon the part of the workmen as to preclude 
the possibility of a first-class job. Now from the driving of the first rivet in the 



iii8 



USE. 



keel to the launch of the vessel the continuous clatter of air riveters, caulking 
tools and the whirring of rotary drills are sure indications of rapid progress 
toward completion. 

Probably one of the largest and best equipped air plants for the use of 
small tools is located at the works of the Newport News Shipbuilding and Dry 
Dock Co. Comparatively new, this air plant now furnishes the power for the 
majority of the tools used on the outside work of the various naval and merchant 
vessels building there, to the exclusion, almost, of steam and electricity. 

The original plant consisted of a small Rand compressor and a few tools; 
then a couple of Pedrick and Ayer compressors and more tools were added. Now, 




FIG. 480^P0RTABLE RIVETER IN OPERATION. 



hardly more than three years since the starting of the initial plant, there are in 
operation two large Ingcrsoll-Sergeant compressors, viz : 

One class G, duplex compound compressor with 20-in. steam cylinders, 
20^-in. high pressure air cylinder and z^Y^-m. low pressure air cylinder and 24-in. 
common stroke. This engine has a receiver inter-cooler 36-in. diameter by Q ft. 
6 in. long, and discharges 2,200 cubic feet free air per minute at 100 lbs. pressure. 

One class G, duplex compressor, with 20-in. diameter steam and 20% -in. 
diameter air cylinders and 24-in. common stroke, with a capacity of 1,600 cu. ft. 
of free air per minute and 100 lbs. pressure at discharge. 

These compressors are all made with the piston inlet air cylinders, are water 
jacketed and are furnished with a governor automatic pressure regulator. The 
compressed air is discharged into a storage tank common to all at about 90 lbs. 
pressure. 



USE. 



1119 



The storage tanks are a necessity and should be of such size as to enable 
the engines, after once filling them, to run at a moderate speed during working 
hours. 

The tanks are usually provided with pop safety valves, ample drainage, 
and from the first tank a small pipe is led back to the automatic regulator on the 
engine. From this main tank the air is carried by mains to smaller storage tanks 
located at different points in the yard, nearest the centres of work. 

By constructing the storage tanks with a baffle plate down the center, the 
air entering at the top impinges upon the plate, delivering the entrained water 




FIG. 481 — CHIiTlNG, CAILKINC; AND RIVETINC WITH PNEUMATIC TOOLS. 



into the bottom of the tank, from whence it is drained at intervals. The air then 
passes under the baffle plate and out again at the top of the tank. The air pipes 
should always enter and leave the storage tanks at the top. 

'Vhe yard is piped throughout. The main air pipe is about 1.500 feet long, 
of cast iron, with leaded joints, 8 in. inside diameter and reduced at intervals to 
6-in. and then to 5-in. At thr end it enters a' reheatcr similar to a surface con- 
denser about 27-iii. diametcM- and 6 feet long, with wrought imn tubes iJ4-in. 
diameter, and is there heated by the exhaust steam, fnmi (ine (if the shop engines. 
This reheated air is employed to run a regular type .\tlas borizontal steam engine 



ii8 



USE. 



keel to the launch of the vessel the continuous clatter of air riveters, caulking 
tools and the whirring of rotary drills are sure indications of rapid progress 
toward completion. 

Probably one of the largest and best equipped air plants for the use of 
small tools is located at the works of the Newport News Shipbuilding and Dry 
Dock Co. Comparatively new, this air plant now furnishes the power for the 
majority of the tools used on the outside work of the various naval and merchant 
vessels building there, to the exclusion, almost, of steam and electricity. 

The original plant consisted of a small Rand compressor and a few tools; 
then a couple of Pedrick and Ayer compressors and more tools were added. Now, 




FIG. 48C^— PORTABLE RIVETER IN OPERATION. 



hardly more than three years since the starting of the initial plant, there are in 
operation two large Ingersoll-Sergeant compressors, viz : 

One class G, duplex compound compressor with 20-in. steam cylinders, 
2oK-in. high pressure air cylinder and 32^-in. low pressure air cylinder and 24-in. 
common stroke. This engine has a receiver inter-cooler 36-in. diameter by 9 ft. 
6 in. long, and discharges 2,200 cubic feet free air per minute at 100 lbs. pressure. 

One class G, duplex compressor, with 20-in. diameter steam and 20% -in. 
diameter air cylinders and 24-in. common stroke, with a capacity of 1,600 cu. ft, 
of free air per minute and 100 lbs. pressure at discharge. 

These compressors are all made with the piston inlet air cylinders, are water 
jacketed and are furnished with a governor automatic pressure regulator. The 
compressed air is discharged into a storage tank common to all at about 90 lbs. 
pressure. 



USE. 



19 



The storage tanks are a necessity and should be of such size as to enable 
the engines, after once filling them, to run at a moderate speed during working 
hours. 

The tanks are usually provided with pop safety valves, ample drainage, 
and from the first tank a small pipe is led back to the automatic regulator on the 
engine. From this main tank the air is carried by mains to smaller storage tanks 
located at different points in the yard, nearest the centres of work. 

By constructing the storage tanks with a baffle plate down the center, the 
air entering at the top impinges upon the plate, delivering the entrained water 




FK.. 481 — CHIl'l'lN(i, CAILKINC; AND KIVETINC WJTH PNEUMATIC TOOLS. 



into the bottom of the tank, from whence it is drained at intervals. The air then 
passes under the baffle plate and out again at the top of the tank. The air pipes 
should always enter and leave the storage tanks at the top. 

The yard is piped throughout. The main air pipe is about 1.500 feet long. 
of cast iron, with leaded joints, 8 in. inside diameter and reduced at intervals to 
6-in. and then to 5-in. At the ond it enters a* rchcatcr similar to a surface con- 
denser a1)()ut 27-in, diameter and 6 feet long, with wrought iron tubes I'^-i"- 
diameter, and is there iieated by the exhaust steam, from one of the shop engines. 
This reheated air is employed to run a regular tyi)c Atlas liorizontal steam engine 



II20 USE. 

that furnishes power for a large band sawmill. The exhaust air from this engine 
is employed to force the sawdust from the mill as it accumulates. The air pipe 
to the engine is 3^ -in. diameter and the exhaust 43^-in. diameter. The reheater 
also supplies air to a small motor for a saw grinding machine. 

At any point in this system the pressure gauge will register the same as at 
the main tank, and even under the most unfavorable circumstances, there is but 
little appreciable drop. There are four other mains leading from the storage 
tank, two 4-in., one 3-in. and one 2j^-in., all wrought iron pipe with screwed 
joints. All pipes used in connection with this plant are buried in trenches below 
the frost line. 

The 2^-in. main has supplied power sufficient for twenty-eight No. 2 Boyer 
hammers and four drills, but this was the full working limit of the pipe; about 
two-thirds this number would be a preferable load. The hammer supply nozzle is 
54-in. and the drills ^-in. pipe taps. The yard has used nearly every type of 
pneumatic machine that is manufactured and even now have many different types 
in use. 

Some of the different operations performed by the tools are shown in the 
pictures given herewith. In everyday use many of the tools work more satis- 
factorily than others, in the matters of economy, in the use of air, freedom from 
breakdown and the not least important absence of vibration. Indeed, some tools 
which work satisfactorily in the first two named respects, are very severe on the 
workmen. They are all liable to break in one part or another, but the manufac- 
turers are constantly improving and strengthening the weak parts as they are 
taught by experience. 

The pneumatic riveters are a little larger than the hammers or caulkers, 
with a head that fits the head of the rivet. The work of driving the rivet is done 
by a large number of comparatively light blows instead of a single squeeze as in a 
hydraulic machine. This permits of the use of a very light frame for holding the 
riveter. The latest type is that patented by the Detroit Dry Dock Company, and is 
made of 2H-in. W. I gas pipe, bent to a U shape, with a gap of about 60 in. 
This frame enables the workman to reach rivets that are absolutely unapproach- 
able otherwise than by hand riveting. Nearly all makes of pneumatic drills are 
practical ; some are more powerful than others for the same weight. Their great 
difference is in their economy. All are extremely liable to breakage in some minor 
points, and a small repair shop is a necessity where many pneumatic tools are used. 
The drills are made in three types, the movable cylinder, the movable piston and 
the rotary, similar to the rotary pump ; these last are great consumers of air and 
are not to be recommended where economy is a feature. The movable cylinder 
type, at the present date, seems to be the most economical and is at the repair 
shop the least often, considering the amount of work done by it. 

It is necessary that care be taken to keep these machines clean, well oiled 
and in good working order. Proper lubrication is an essential requirement, both 
as to quality of oil and frequency in applying it. The best winter strained lard oil 
or valvoline sewing machine oil are recommended. Should it become necessary 
to clean the machine, admit kero.sene and turn slowly while the grease is dissolv- 
ing and when all is dissolved admit air through the throttle. Thoroughly lubricate 
again before using. 



USE. II2I 

As these machines are made interchangeable, the parts most liable to break 
should be duplicated in store. These cost but little and afford a most excellent 
insurance against stoppage from breakdowns. 

For work in the frame sheds, on bulkheads and reverse frames the Caskey 
or single squeeze pneumatic riveter is used. This is a very good and efficient 
tool; it is usually slung from a jib crane with a long jib, by a chain twist, and 
thus commands a large area. 

The larger illustration on page 1118 shows this riveter at work on the double 
bottom of a battle ship. A track was laid down the center of the inner bottom. 
This was for the crane carriage. The riveter, as shown, is held by a pneumatic 
hoist. This was found to be a poor arrangement, as the elasticity of the air in 
the pneumatic hoist prevented a rapid setting of the hammer on the rivet. A 
Weston chain hoist was afterward, used with success. 

For general work about the yard a seesaw arrangement was devised, con- 
sisting of a beam, supporting the riveter at one end, with a counter balance at the 
other. The beam rested on an A frame carriage. This allowed a great latitude 
of movement and was eminently successful. It is shown on page 11 17. 

The amount of work done by these pneumatic machines is greatly dependent 
upon the workman, and the men must be picked by actual trial to secure the best 
results. 

William Burlingham. 



HYDRAULIC AIR COMPRESSION. 

The development in the method of hydraulic air compression, which has 
advanced materially within the past few years, has an interesting and important 
history. Our files are replete with information on this subject. The principles 
involved were first substantially shown in the "Trompe" or hydraulic blower or 
forge blast, which is a very simple, effective and strikingly ingenious method, 
and is understood to have been invented in Italy in 1640. The fundamental prin- 
ciple is that falling water is utilized for the compression and conveyance of air 
into suitable reservoirs in which it accumulates, and from which it is drawn 
and applied as a power. Under certain conditions, the system of hydraulic air 
compression has advantages over mechanical forms, and these conditions arise 
when water power is present or adjacent. It can be used at any point where 
there is a sufficient fall to give the desired pressure. There are sources of loss 
inherent in the use of mechanism, such as the loss arising from the development 
of heat, friction, etc., that are largely obviated in the hydraulic compressing 
system. 

The principles of the "Trompc" seem to pervade every patent or device 
that appears on this subject. The only fault in the early "Trompe" which has 
been overcome by the latter devices, is in low pressures and efficiency. In the 
"Trompe" blower forges only from ij/^ to 4 ins. of water pressure were needed, 
and the "Trompe" remained as an air compressor suited to the wants of a forge 
at the low efficiency of from 10 to 15 per cent. 

The "Trompe" shown in Fig. 482 is a large cistern, which is supplied with 
a constant stream of water and connected with another cistern vertically under- 



1 1 22 USE. 

neath it by means of wooden pipes, each measuring some 20 ft. in length. The 
length of these vertical pipes is not a constant quantity, but 20 ft. is a fair average. 
This lower cistern has two openings, one at the top, by which air gets away 
through the tuyere into the furnace, and another on one side near the bottom 
through which the water can get away. The openings of the vertical wooden 
pipes connecting the two cisterns are in the upper cistern partially closed by a 
kind of wooden funnel which causes the water to descend in the middle of the 
pipes instead of clinging to the sides, as might otherwise be the case. In the 
upright pipes, and a little below the upper cistern in an inclined direction, are 
several small openings, their inclination being downward. The flow of water into 




FIG. 482— THE ''tROMPe/' OR HYDRAULIC BLOWER. 

the upright pipes is regulated by plugs, one of which is shown. The v,^ater 
descending is directed into the center of the pipes by the wooden funnel. The 
descending water produces an "induced current" under the influence of which 
air is drawn into the pipes through the small inclined apertures, and passes on 
in considerable quantity along with the water down the pipes. In the lower 
cistern immediately below the vertical pipes is a board on which the water and 
air dash, and in doing so separate, the water going to the bottom of the cistern, 
and the air making its way through the tuyere into the furnace. This simple 
construction provides for the compression of air at a very low pressure. 

The first experiments leading to high air pressures were made by J. P. 
Frizell, of Boston, Mass., in 1877. An account of his invention, on which a 
patent was granted Jan. 29th, 1878, was published about that time. This patent 



/' 



r 



USE. 



1123 



seems to claim all of the essential features of the patents which have been granted 
since on similar methods. Patents have been also granted to C. H. Taylor, 
Adolph F. Du Faur, the late Col. George E. Waring and others, covering the 
features practically the same as in the original "Trompe," with the arrangement 
and construction of parts designed to bring the efficiency of the system up to a 
practical point. The patent granted to Col. Waring adds a stroke to nature by 
using a blower or compressor for adding more air to the water descending the 
shaft. 

Frizell's patent indicated a mode of transforming the power of a waterfall 
into compressed air by the arrangement suggested in Fig. 483. At a point above 
the dam a vertical shaft is sunk to a depth corresponding to the pressure re- 
quired. For a pressure of 100 lbs. per square inch the clear depth would be 231 
feet. Thence a horizontal tunnel extends to a point below the dam, meeting an- 
other vertical shaft which reaches the surface. The top of the tunnel is not 
exactly horizontal, but rises slightly from both ends toward the middle, at which 




FIG. 483. 



point a chamber of sufficient capacity is excavated in the rock, whence the air is 
drawn off through a pipe. The whole forms thus an inverted siphon, through 
which the water flows with a velocity depending on the effective head. The 
length of the tunnel will be controlled by the necessity of placing the entrance to 
the chamber far enough from the descending branch to admit of the complete 
escape of the air bubbles. The effective head will depend on the hydrostatic dif- 
ferences of ingress and egress of the water in the inverted siphon, and regulates 
the quantity of air carried by the descending branch. This can be regulated at 
will, and furnishes the means of controlling the velocity. Fig. 483 shows the 
method proposed for inducing the air bubbles into the descending column, though 
it is probable that a simpler method would disclose itself in the practical operation 
of the apparatus. The entrance to the vertical shaft is surrounded by a bulk- 
head of masonry. Over this bulkhead the water is led in a covered channel 
whose bottom rises a little above the highest level of the water in the pond, form- 
ing a siphon. The arched space below the siphon and above the masonry forms 
an accessible gallery, drained by a pipe which discharges below the dam. This 
gallery contains the cocks for regulating the admission of air. They are shown 



1 1 24 USE. 

at A on the descending branch of the siphon channel, where its direction is 
nearly vertical. At this point the pressure within the siphon is less than that 
of the external air, and it will flow in through any opening. 

The Frizell experiments cover broader ground than his patent claims. 
They suggest a good study of other forms for introducing air into the falling 
water tubes that may prove useful and lead to a higher efficiency. The efficiency 
in Frizell's early experiments was 26 per cent. Later by a larger apparatus he 
obtained an efficiency of 52 per cent, with a head of 5 feet. 

The Taylor system has received considerable attention from the engineer- 
ing press, and is familiar to the readers of Compressed Air^ as a description of 
the plant at Magog, Quebec, and at Ainsworth, B. C, has been given in these 
columns. The efficiency of the Taylor compressor is said to be 62 4-10 per cent, 
at 52 lbs. pressure, the compressor furnishing one cubic foot of free air com- 
pressed to 52 lbs. by a fall of 4 cubic feet of water 22 feet. 

It is claimed that the air compressed by the hydraulic system has some 
advantages over air compressed in a cylinder, in that the air delivered will be 
drier than the external atmosphere and of the same temperature as the water 
which compresses it. This claim appears to be well taken. Persons without 
experience with compressed air naturally infer that air compressed hydraulically 
and in contact with water will be moist. In mechanical compression we have the 
"dry" and the "wet" system. The dry system is that where compression takes 
place without water contact, cooling being effected by jackets; and the wet sys- 
tem is that where cooling is effected by a spray of water introduced within the 
cylinder. 

At times it has been noticed that air from the dry system has given more 
trouble from freezing than that from the wet system. This is due to the fact that 
in the latter when water is introduced in the cylinder in sufficient quantities and 
at low temperatures a condensation of moisture takes place, the cold water acting 
like a condenser and absorbing some of the moisture that was in the air before 
it entered the compressor. This is strictly in keeping with the laws that govern 
condensation of moisture in atmospheric air. There are certain hydraulic systems 
of compression which add moisture to the air; among them is the hydraulic 
piston compressor. This is because the compression takes place rapidly. Heat 
is generated, and there are not sufficient points of contact of air and water to 
reduce the temperature of the air below the dew point. The "Trompe" system 
appears to be admirably adapted for furnishing dry air. The compression takes 
place slowly, and in air bubbles separated probably one from the other and dis- 
tributed through the water column. It has been called the Pohle pump re- 
versed, and we know that in pumping water by the Pohle system compressed air 
admitted at a higher temperature than that of the water is discharged at a lower 
temperature; in other words, the air is cool by thorough contact with water. 

The "Trompe" system does not, as some suppose, require much head of 
water; on the contrary, a few feet of head are sufficient for ordinary purposes. 
What it requires is large water volume and a deep well. Nor is this system a 
competitor of the mechanical system of compression. The best engineering is 
that where a result is accomplished in the most economical manner. Where 
plenty of water exists and there is a chance to get a few feet of head, where 
the water does not cost much to use, and where a shaft or well may be sunk at 



r 



USE. 



1 125 



reasonable expense, a "Trompe" air compressing system should be recommended. 
♦ At the present time the Taylor system appears to be the most efficient for this 
purpose, and may be recommended as the best. Experience will probably still 
further improve the efficiency by increasing the volume of air compressed by a 
certain volume of water. A combination system might also in some cases be 
recommended. By this we mean a plant which compresses the air to low pres- 
sures hydraulically, the compressed air being then drawn into an air compressor 
and recompressed mechanically. We believe that there are large possibilities in 
this connection, as it is difficult by mechanical means to abstract the heat of 
compression during the early stages in the stroke of the machine. The tempera- 
ture rises rapidly and in greater proportion to the pressure during the first half 
than during the second half of the stroke of an air compressor, and the percentage 
of increased power required to effect compression is thus greater. The "Trompe" 
system affords a means by which cold and dry compressed air at low temperatures 
may be compressed by air coinpressors with economy. Such a combined plant 
need not require excessive depth of shaft or well, and should be recommended in 
places where sinking is difficult. 



A REMARKABLE CHIP. 



The illustration shows the reproduction of a chip taken from a piece of 
steel by a No. 2 Boyer Pneumatic Hammer. It was taken off by a workman in 




Hi. 4tS4 — dill' (o- 



A BON Kl< 1'iNh.lM AIH li A i\i M KK. 



Cramps shipbuilding yard at Philadelphia. The chip is z'-9" long, ^" thick — 
width. It was removed at the rate of one foot every four minutes. One man 
with this hammer chipped as much in two minutes as two men did in six minutes. 
The hammer only weighs eight pounds. The piston has a 4J/2" stroke and strikes 



1 126 USE. 

i,8oo strokes per minute. The Chicago Pneumatic Tool Co., makers of the above 
tool, has a number of sizes of chippers and hammers which are reported to make 
equally good records in the class of work for which intended. 



DEATHS AMONG CAISSON WORKERS. 

Deaths among caisson workers have been investigated by Drs. R. Heller, 
Wilhelm Meyer and Hermann von Shrotter, and the results are contained in a 
paper in the Centralblatt der Bauverzualtung, for Dec. i8, 1897, written by Mr. L. 
Brenecke. In 129 deaths among workers in compressed air, 38 men were divers 
and 91 caisson workers. These doctors agree with the theory of Paul Bert, of 
Paris, that the danger lies, not in the high pressure, but in a too rapid reduction 
of pressure. This is shown by the fact that a sudden reduction from + 0.3 at- 
mosphere to the normal has caused death ; while a pressure of + 5.4 atmospheres 
was followed by no evil results when 3 hours 3 minutes were consumed in re- 
ducing this pressure. They agree that in all except exceptional cases, no deaths 
will occur if 2 minutes are allowed in reduction, for every 6.1 atmosphere in ex- 
cess of the normal pressure. They also propose a hospital air-lock where pressure 
of more than + 1.5 atmospheres are to be used, so that the sick may be treated 
under pressure. Workmen should be housed in barracks where they can be kept 
under medical control. — Engineering News. 



AIR ON WAR SHIPS. 



Several war ships and other vessels have been provided with a system for 
closing bulkhead doors in case of a leak or accident. The most approved system 
is one that uses compressed air. The "Long Arm" system is used on the U. S. 
protected cruiser Chicago, and by its application in an instant the doors of the 
bulkhead can be closed. A central station for compressing the air may be placed 
in any convenient location and usually consists of a smc»ll three stage air com- 
pressor, operated by steam or electric motor, with an air receiver consisting of 
the required number of storage flasks for the desired emergency capacity. Air 
is kept in the receiver at about 1,000 lbs. pressure and it is used at 150 lbs. pres- 
sure, and there is always enough power stored to operate all of the doors with- 
out having to wait until the air is compressed. The pipe line runs to all points 
where the closing mechanism is located, and is controlled from an emergency 
station automatically. The door slides vertically between two guides. A cyl- 
inder is attached to the door and a piston moves it up or down. In case of 
need the pipe line is opened and the pressure exerted on the piston head forces 
the door down and closes it. Some interesting experiments have been tried with 
this system. In one instance a pile of wet coal lying 30 in. deep above the sill 
obstructed the closing door, but the water swept it away and the door closed 



USE. 



1127 



(against the water pressure. In another case the door closed down upon the 
coal and was locked in that position. From the progress being made by the 
"Long Arm" System Co., of Cleveland, Ohio, it is likely that they will succeed 
in extending their system to every branch of marine service. 



TILDEN PNEUMATIC HAMMER. 

The cut herewith shows that type of pneumatic engines in which the 
reciprocating piston constitutes a hammer, adapted to deliver a series of rapidly 
recurring blows to a chipping, caulking, beading, riveting or other tools, the 
shank of which is located in the path of such impact piston, and constitutes an 
end closure for the lower piston chamber. 

The objects of the present improvements are: First, to provide a simple 
and efficient sectional formation and arrangement of the main cylinder for the 
impact piston, and the valve block and housing for the reversing valve, which 
permits of a ready and convenient detachment of the parts for cleaning, etc. 
Also to provide means for connecting the handle, main cylinder and valve block 




FIG. 485 — TILDEN PNEUMATIC HAMMER. 



and housing together in a rigid and substantial manner. To provide means, 
self-contained within the hammer, for automatic lubrication of the hammer parts 
while in operation. To overcome recoil and dispense with the vibration or jar 
(so objectionable in most hammers) which enables the operator to accomplish 
greater results with less fatigue. In this hammer there are but two moving 
parts, the piston and valve, which, by the arrangement of the air passages, con- 
trol each other. 

The sectional view herewith gives an idea of its construction and opera- 
tion. Starting with the parts in the position as illustrated, the motive fluid or 
compressed air from the main chamber passes through ports into the valve 
block chamber to press upon the upper end extension of the impact piston, and 
acting against the decreased area thereof imparts a light initial movement to 
the piston, which from practical experience is found to be very efficient in re- 
ducing the amount of jar or vibration. 

Letters patent were issued Oct. 24, 1899, to Robert Burns and B. E. 
Tilden, and the manufacture of same will be immediately commenced by the 
International Pneumatic Tool Co., of 1209 Monadnock Block, Chicago, 111., 



1 128 USE. 

under the mangement of B. E. Tilden and C. J. Fellows. To designate this 
from other hammers it is called "The Tilden." 

At the shops of John Mohr & Sons in Chicago, tliey reported that an in- 
experienced man with one of these hammers accomplished the same amount of 
riveting in 30 hours for which their experienced riveters had previously required 
80 hours, and that all was first class and steam-tight when tested under pressure. 

They are so well adapted to all classes of work that orders are coming 
in practically unsolicited. They mark a great advance in pneumatic hammers. 



COL. BEAUMONT, R. E. 



Col. Beaumont, R. E., of England, who died in London recently, was an 
engineer of experience and much ability, especially in pneumatics. In 1880 a 
system of pneumatic traction, designed by Col. Beaumont, was put into experi- 
mental use at the Woolwich Arsenal, London. The interesting point about this 
experiment is the fact that compressed air was used at high pressure and the 
engine was so constructed that it might utilize the entire power stored in the 
air, no matter how high the initial power might be. One thousand pounds per 
square inch was the pressure which Col. Beaumont thought best for this pur- 
pose. The air was admitted into successive cylinders, having different areas, 
commencing first with the smallest, and compounding ?s the pressure was re- 
duced. 

Provision was made for a larger consumption of air as the pressure fell in 
the reservoir. It is easy from our point of view to-day to anticipate difficulties, 
which might arise in such a system as this. In the first place, the condensation 
of the moisture in the air would naturally cause an accumulation of water in the 
cylinders, and would result in freezing and interference with the machinery. 
This was at a time, too, when the Mannesmann steel tube had not been con- 
structed and it was difficult to maintain air at high pressure in safe storage ves- 
sels. Like most pneumatic tram car experiments, this one was not continued to 
a successful issue for the lack of funds, but it is of special interest, in that it was 
a high p:-essiu-e system, as distinguished from the low pressure systems which 
followed it, and which were approved by engineers up to recent years. Col. 
Beaumont was a firm believer in the high pressure system and held his views on 
this subject to the last. He believed in storing the air at high pressure 
on the cars, and in accomplishing pneumatic traction by the storage system, 
as distinguished from that which picks the air up at intervals along the line. 
Of the latter system, the Mekarski, Popp-Conti, Hughes & Lancaster, and Jarvis 
are conspicuous examples. The two systems now in operation, known as the 
Hoadley-Knight and the Hardie, are those of high pressure, and follow the 
Beaumont idea, which is now made practicable by the use of the reheater, and the 
Mannesmann tube. By means of the reheater the temperature of the air is 



•ft 

USE. 1129 

raised so high, that freezing, even in compound cylinders, does not take place, 
and the Mannesmann tube furnishes a means by which air at high pressures may 
be safely stored in small areas. 



BRUNEL. 

Facing the Thames embankment in London is a statue of Brunei, the 
great English engineer. Brunei was prominent in many things, but it must not 
be forgotten that he was the first man to practically apply compressed air for 
commercial service. Compressed air, though as old as the hills, dating back to 
the time of Hero of Alexandria, was of little use to the world except for experi- 
mental purposes until Brunei used it in sinking caissons while building bridges 
over the Thames. Its importance for caisson service cannot be overestimated, as 
without it, it is doubtful that we should have built such piers as those at the 
Brooklyn Bridge, the St. Louis Bridge, and many others, where deep foundations 
are necessary. The use of compressed air in caisson service led to its use in 
diving bells, which were at one time of great importance in excavating under 
water. Of late years the diving bell has been replaced by the diving suit, and 
this is also an important use of compressed air. 



DEATH OF THOMAS DOANE. 

Thomas Doane, of Charlestown, Mass., the well-known civil engineer, died 
October 22. He was born at Orleans, Cape Cod, in 1821, and after attending the 
Andover Academy he entered the office of Samuel L. Felton, a noted engineer. 
After remaining with him for three years he became engineer of a division of the 
Vermont Central Railroad. Mr. Doane was connected at one time and another 
with all the railroads running out of Boston. In 1863, he was appointed chief 
engineer of the Hoosac tunnel. He located the line of the tunnel and built the 
dam in the Deerfield River to furnish water power. In this work he introduced 
nitro-glycerine and electric blasting for the first time in this country. In Febru- 
ary, 1875, he ran the first locomotive through the tunnel. In 1869 he went to 
Nebraska, and built 240 miles of railroad on the extension of the C. B. & Q. R. R. 
He made the question of grades a special study, and so perfect were those on the 
extension that one engine could haul as many cars to the Missouri River as five 
engines could haul across Iowa. When in Nebraska he took a leading part in the 
agitation of the question of establishing a college in that State, and in recognition 
of his services the institution was named Doane College. 

It is in his connection with the Hoosac Tunnel that Mr. Doane devoted 
himself to the perfecting of compressed air machinery. He introduced com- 
pressed air and invented and patented machinery for it, and had a large share in 
inventing the pneumatic drill and their carriages used there. 



1132 



USE. 



track return of electric street car lines. Charles A. Stone and Howard C. 
Forbes discuss the same subject, as it occurred in Boston, with practically the 
same conclusions in the Journal, N. E. W. Association in 1894. The results of 
electrolysis and its corrosive action is described by Inspector Stewart, of St. 
Joseph, Missouri, the same year. It is so evident, that the American Water 
Works Association appointed a committee to recommend preventive measures, 
and received its report at their meeting in 1894. A writer in Cassier's Magazine, 
April, 1895, discussed the legal aspects of electrolysis, and determined that elec- 
tric railways should furnish whatever is necessary to minimize electric corrosion, 
and would probably be held liable for damage. 

The subject has received treatment from city engineers and others who 
are connected with public works, and who have the responsibility of such matters 
on their hands in all parts of the world. 

Electric traction has proved a dangerous element in municipal under- 
ground work. It is a silent destroyer of pipes, and a menace to public health, 
through the escapement of gas and sewage. 



NOTES. 

A novel application of compressed air has recently been patented on a 
"Compressed Aid Mechanism for Vehicles and Other Devices." With this 
simple device the inventor, F. Schumacher, of 148 Sackett street, Brooklyn, N. Y., 
proposes to reduce the friction on the axles of heavy rolling stock, by confining 




FIG. 488 AIR LUBRICATED BEARING. 



a volume of compressed air in a system of pistons and chambers in such a manner 
so as to enable the axles of a vehicle to rotate against the air pressure without 
friction. 

The illustration shows the principle of the invention as it is applied to a 
freight railway truck. Every detail of the operation of the device is automatic, 
simple and positive. The arrangement consists of a pressure accumulator, air 
chambers for the axles, and a pressure regulating mechanism. A pump and a 
small storage tank constitute the automatic pressure accumulator, and maintains 
the necessary pressure. It may well be compared to the inflation of a pneumatic 
tire; once filled, it lasts for a long time. From the storage tank the pressure is 



USE. 1133 

regulated by a governor, admitting and expelling the air to and from the cham- 
ber "a" and the space "e" below piston "P" in pot "K," chamber "a" and space 
"e" being connected by a pipe "w." The adjustment of the governor is such that 
the pressure in these spaces is maintained proportional to the load to be maintained 
by the air. The pot "K," with piston "P," serves to regulate the pressure under 
load vibrations, reducing or increasing the volume in "a," "w" and "e," without 
admitting or expelling any air to or from said air spaces. The load resting on 
bolster "O," spring "P" and piston "P," enables the air in "e" to exert an anti- 
vibrational influence upon the same, absorbing all trembling vibrations of the 
vehicle not absorbed by the spring. 

The fittings on the axle consist of a collar "S," easily removable ; a bearing- 
block "X," with its piston-shaped lid "V," a box or casing "U," for the axle, and 
a frame "W," for casing "U." 

The bearing-block "X," has a cylindrical top for "V" and a recessed sur- 
face for an air space "a." It being fitted air tight to "V" and "S" no air can 
escape, and "S" can rotate with axle "A" against the pressure in "a." 

Any number of air-chambers on the axles may be connected to one pot, 
"K," it being only necessary to properly proportion the combined lifting areas 
between the chambers of the axles and the lifting area of the air in pot "K." 

The pressure in the storage tank is at all times greater than the pressure 
in the chambers of the axles and connections, it being in the latter spaces at a 
maximum of 175 lbs. on railing cars, and considerably less for lighter vehicles. 
The advantage claimed in the application of this device to heayy rolling stock is 
the following: 

Frictional reduction of over 90 per cent. 

A longer life of the bearing. 

The saving of over 75 per cent, of oil. 

A positive prevention of hot bearings. 

Increased safety for the rolling stock. 

Increased speed of fast trains. 

Better comforts for the traveling public. 

Smaller coal bills. 

Smaller motors. 

Decreased expenses in street railway equipment. 



There has been considerable demand for a light, durable and easily handled 
breast drill, and the Empire Engine and Motor Co., of 26 Cortlandt street, New 
York City, has just brought out a machine to meet it. We show cut here of their 
No. Pneumatic Breast Drill, a machine that has created the most favorable im- 
pression wherever it has gone. It weighs but 10^ pounds, with 60 to 70 pounds 
pressure, and with a 5-16 drill will go through 2 inches of ordinary cast iron in 
a minute. This is an invaluable tool for doing all classes of light drilling in 
fitting work, and driving test holes in columns in bridge and architectural iron 
works ; driving test holes in stay bolts and running a burr drill for stay bolt holes 



II34 



USE. 



in locomotive and railroad shops ; boring for lag screws and running them in car 
building shops; running augers and driving in screws for general wood work; 
boring for name plates and drilling and tapping for putting on lagging. 

We have enumerated a few of the uses to which this handy little tool can be 
put and for which it is well adapted. It is exceedingly compact and well made, 




FIG. 489— PNEUMATIC BREAST DRILL. 

as a glance at the cut will show, and easily operated, a simple turn of the wrist 
being all that is required to start or stop it. The motor is of the rotary piston 
type, with the gearing all enclosed in the case. It is very durable, there being 
nothing to cause excessive wear and nothing to get out of order. 



The purifying of alcoholic liquors is accomplished by compressed air through 
the Gushing process, which has been in vogue for many years. The liquor is 
placed in receptacles for the purpose and air, after it has been washed and purified 



r 



USE. 



1 135 



by Prof. Tyndall's well-known method, is compressed and forced through perfor- 
ated pipes entering the liquor in minute streams. The liquid is violently agitated 
and the air permeates every portion of it. The air being warm, oxidizes the fhsel 
oil and at the same time volatizes and expels into the open air the light poisonous 
ethers, leaving the liquors thoroughly pure and free from aldehydes. It is claimed 
that by this process new liquor for medicinal purposes is made practically as good 
as old and that the drinking of liquor treated thus does not cause stupefaction, 
headaches and other disagreeable results. 



We show herewith a rather novel application of the pneumatic hammer. 
On the end of the piston rod of the machine is placed a saw blade which is recip- 




Flt;. 4g0^A PNEUMATIC HAMMER-SAW. 



rocated rapidly, approximately to 1,000 strokes per minute, and in this way a 
pneumatic saw of very handy construction and rapid work is made available. 
Here is a portable hand saw, which may be placed in any position and which, 
without exertion on the part of the operator, is capable of doing very rapid 
and economical work. This saw can be operated by a boy when used 
for common work. It should be useful in pattern shops, for cabinet work 



1 136 



USE. 



and for wood carving. We have been informed that this machine is in practical 
operation in a packing house in Chicago, and that it is used there for the purpose 
of sawing ham bones. 



The Standard Railway Equipment Co., of Chicag6 and St. Louis, are intro- 
ducing a new design of pneumatic wood drill, which is known as their Monarch 
No. 2. This drill is provided with ball bearings throughout. It is formed with 
ball bearings throughout. It is formed with a solid three point crank of tool steel 
hardened where the bearings of the various ball races are. Each bearing has two 




FIG. 491 MONARCH DRILL. 



sets of balls. The spindle is on one side of the working part of the machine, mak- 
ing the engine entirely independent and in that way any undue strain put on the 
spindle cannot affect the engine part in any manner. The drill is reversible, 
having the reversing and throttle valve made in one piece, so that by simply turn- 
ing same to one side or the other will give the machine a forward or backward 
motion. 

Another feature found in this drill is that the exhaust is provided with a 
muffler, so that the machine is practically noiseless while being operated. It is 
claimed that this drill is very economical in the consumption of air and will bore 
any size hole up to two and one-half inches in diameter in any kind of wood. 



USE. 



1137 



Weight of drill is but seventeen pounds, which makes it very desirable around 
car shops. The accompanying cut shows this machine in operation boring side 
plates in car repair yard. 



The accompanying illustrations show the Quick Acting Stop Coupling for 
Air Hose made from a design of Mr. E. B. Gallaher, engineer of the Pneumatic 
Supply & Equipment Co., N. Y. 

This coupling is designed especially for use in connection with pneumatic 
tools. It is both a union and a stop cock combined, and its use is desirable where 




FIG. 492 — QUICK ACTING STOP COUPLING FOR AIR H( 



rompressed air tools or appliances are used. The operation is extremely simple 
—it may be locked or unlocked by a quarter turn and when locked it is abso- 
utely air-tight under any working pressure. It is claimed that a saving of com- 




FIG. 493 — QUICK ACTING STOP COUPLING FOR AIR HOSE, COUPLED. 

•ressed air is effected and the necessity of shutting off Ihe air supply at the 
ccciver or main supply pii)c is avoided. The use of this coupling permits one 
ool to be detached and another one to be connected to the air hose instan- 
aneously and the annoyance of twisted hose is entirely obviated. 



II38 



USE. 




FIG. 494 — HENRIKSON S FLUE CUTTER. 



The Henrikson Flue Cutter for 4^^" flues, is shown in the accompanyi 
cut. This is a newly patented article and has been found very successful 
operation that is now being manufactured and sold by the Chicago Pneuma: 
Tool Co. It is made in any size to suit requirements, and has been adopted 
standard on the Chicago and N. W. R. R. The cutting wheel is fed against t 



USE. 



f39 



flue by the cylinder and prston arrangement, shown about the middle of the 
machine, the air pressure passing through the motor to operate the piston, and 
the air motor revolving the cutter at the same time. The machine will cut oflf 
the flues either inside or outside the flue sheet and on 4%" flues it has been 
found very efficient, cutting them off in about 20 seconds, and in much less time 
on locomotive flues. 

Any railroad mechanical man will very quickly appreciate the advantage of 
this tool, on account of the great saving effected in that the machine cuts off the 
flues close to the sheet, thus making but very little waste on the flues. 



There has recently been placed on the market by the Standard Pneumatic 
Tool Co., a new pneumatic tool, designated as the "Little Giant" Pneumatic 
Reversible Boring Machine No. 5, designed especially for work around railroad 




FIG. 495 — LITTLE GIANT DRILL. 



car shops. Being very compact and light in weight, which permits of its being 
easily handled and operated, and very efficient in all classes of boring into wood. 
It is made of steel throughout, and can be operated in a bath of oil, as exhaust 
does not come in contact with working parts. 

One of the principal features of this machine is that it is reversible, as by 
;«. slight turn of the handle it can be reversed running at full speed, withdrawing 
the auger instantly. The advantages of this is apparent, particularly when boring 
holes in cars. It is geared to run at a high rate of speed, and is so constructed 
that it will last for a long time without getting out of repair. It has double- 
balanced piston valves which cut off at ^ of full stroke, consequently is very 
economical in the use of air. The weight of this machine is 12 pounds, and is 
capable of boring into wood up to y/y inches in diameter to any depth. An effort 
has been made to make this a superior pneumatic boring machine, and at the pres- 
ent time the claim is made that the success obtained under exhaustive tests and 
comparisons proves everything claimed for it. 

When a firm takes pleasure in sending machines on trial to any one desiring 
to test its efficiency, and will pay the express charges both ways if it fails to meet 



II40 



USE. 



with their approval, and also guarantee the same against repair for one year, it is 
quite certain that the claims can be substantiated, and this the above company 
will do. 



The Gabriel Stay Bolt chuck is arranged to grasp any size stay bolt, and 
will turn them without the necessity of squaring up the ends. In operation with 




FIG. 496 — GABRIEL STAY BOLT CHUCK. 



USE. 



141 



the air motor, as shown, it is very rapid and efficient and effects a great saving of 
labor in turning in stay bolts. 

This is a small machine but great in its labor-saving qualities, and will cer- 
tainly interest all users of such devices. It is an entirely new device, just 
patented, and will commend itself at a glance to all practical men. 



The above illustration shows an apparatus which is used in the candy 
manufactory of Croft & Allen, Philadelphia, Pa. Its purpose is to remove candy 
from the tops of tables where it has been spread in thin layers to harden. These 
tables are provided with rollers for easily running about the place. When the 
candy has become of proper consistency the table is shoved over under the 
Apparatus. It is clamped firmly to the bar A shown underneath. The blade B, 
v/hich is then at the end opposite (C) to where it is in the picture, is forced for- 
ward by means of a piston attached to the blade driving it the entire length of 




FIG. 497 — I'NEl'MATIC CANDY MACHINE. 

Stroke. The blade skims the top of the table, scooping the candy which has 
adhered very firmly. The result is a great saving of labor. It is all done in a few 
seconds, whereas before the apparatus was designed, several men were employed 
to remove the candy. Many tables were required and the limited room was in 
continued confusion. The apparatus was designed by Mr. Howard A. Pedrick, of 
the firm of Pedrick & Ayer, Philadelphia, and while it is a special appliance, it is 
none the less interesting. 



A combined compressed air churn and butter worker has been invented by 
Mr. R. R. Stone, a butter dealer of New York. The churn itself is wooden, 
cylinder shaped, like a barrel, and in it are revolving paddles, which are worked 
by a crank, either by hand or power. Legs support the cylinder and make it 
stationary, and consequently can be well ventilated. The churn is open at the top. 
Air is compressed and cooled, then conveyed through a small copper tube with 
small perforations through the bottom of the churn and escaping at the top, per- 
meating all parts of the cream. Because of the cooling properties of compressed 



1 142 USE. 

air no ice is required, even in warm climates. Churning may be commenced with 
warm cream and cooled as rapidly as desired. By the thorough distribution of 
cold, streaks in the butter are avoided. 



The latest device for economizing fuel in steam furnaces has been brought 
forward by Professor Linde, the first man to put the industry of cold storage on 
a commercial basis. Professor Linde has lately been giving his attention to the 
industrial production of liquid air, in which he has been fairly successful. The 
liquid air can be supplied in any required quantity, but the uses to which it can 
be profitably applied have not developed in the same proportion. Professor 
Linde now proposes to employ liquid air in conjunction with coke or inferior fuel 
in steam boiler furnaces. It is stated that after giving oflf the nitrogen, a gas 
remains that consists of 50 per cent, of oxygen, that can be profitably used in 
boiler furnaces at the present high price of fuel. The idea is distinctly novel ; 
and probably, but for the distinction attached to Professor Linde's name, would 
attract little attention. 



For obtaining an exact idea as to liquid air there is a very simple method, 
in the opinion of M. Robert Pitaval, who makes this observation in UAlumi- \ 
num, and that is to consider it as the extreme limit of compressed air, when one I 
can easily conceive that it may be employed as a refrigerating agent, as motive i 
power, and as explosive force. Again, its composition sufficiently indicates that 
it may be a source of oxygen which, as is well known, has many uses ; but the 
success of all these applications depends upon a principal factor, which is the 
sale price, and consequently the cost price of liquid air. This substance may, in 
fact, serve to afiford liquid oxygen owing to the differences of volatility in the 
two elements which compose it. By evaporating one- half a given mass of liquid 
air as a concentration of oxygen to 85 per cent, is obtained, and, on pushing the 
evaporation further, nearly all the nitrogen may be eliminated. I 



II 



To supply compressed air for the construction of one section of the New 
York tunnel or subway, a steam plant has been erected at the north end of 
Union Square on Seventeenth street at a cost of nearly $100,000, including the 
air piping to the rock drills and other machinery along the section. The plant 
which is erected in one side of the street proper will contain five boilers in bat- 
teries of two and three. The boilers are of multi-tubular type, 60 inches by 16 
feet, set in permanent brick settings with two steel smokestacks about 70 feet high. 
The plant also comprises two large air compressors, a blacksmith shop, small 
machine shop and storehouse for various tools. It is rather surprising to see 
a power plant erected in such a permanent manner right in the street of a large 
city, and for an apparently ephemeral job, but as the construction of this section 



USE. 1 143 

may require two or three years, the expenditure for power purposes will 
undoubtedly be a good investment, as compared with the cost of power generated 
by small portable boilers generally used in work of this character. To avoid 
smoke and cinders coke is used instead of coal. 



John B. Smith & Sons, Toronto, have installed an equipment of compressed 
air hoists in their saw mills and lumber yards, ranging in capacity from J^-ton 
up to 4 tons. So far as can be ascertained this is the first application of this 
mode of handling lumber in Canada. Since its inception a great saving has been 
effected. For example, an ordinary load of lumber can be loaded or unloaded 
by two men in from 20 to 40 minutes less time than formerly. In handling the 
heavy lumber arriving in their yards by trains, less men are required, and a sys- 
tem of overhead tracks permits the lumber to be put right alongside the ma- 
chinery in the mill, with the one handling. In a plant of this kind the fuel being 
so plentiful the first cost is almost all to be considered. The air is compressed in 
the ordinary way, and is stored in a central tank, and distributed to auxiliary 
reservoirs. The rubber hose used is coupled at convenient points with automatic 
valve couplings, which permit of the hose being detached, and as soon as this is 
done the valve prevents any loss of air, thereby the hoist retains its load for any 
length of time necessary for its removal to other parts of the yard or building 
by the trolley overhead. 



Raising sand from the ground floor to an overhead bin by compressed air 
is done at a great many railroad engine houses, but blowing it upstairs with a 
fan blower is not very extensively practiced. 

At the Pennsylvania Railroad engine house, in Louisville, Ky., General 
Foreman Foster uses an old 40-inch fan blower for this work. A smaller blower 
would do the work, but as he had this one on hand, it was installed. A 6-inch 
galvanized-iron pipe leads from the fan in engine room through the sand house 
to an elevated bin about 30 feet high. The sand flows from the bin under the 
sifting platform through a i^-inch pipe into the 6-inch air pipe, where the cur- 
rent of air takes it up the pipe, which lies at an incline of about 30 degrees, into 
the bin. The end of the sand pipe is curved to point the same way the current of 
air is traveling, so that the air does not blow up through the sand into the sifting 
bin. 

At the top of the storage bin there is a pipe, 8 feet high, 12 inches in 
diameter, through which the air escapes. All the sand drops in the bin, while 
the loam and dust are carried out the ventilating pipe. Something over a ton an 
hour can be handled by this method. It is a continuous operation as long as the 
sand is running into the air pipe. 

The fan is run only while the sand is being sifted into the lower bin, and 
it will not run into the air pipe unless the fan is running. The current of air 
seems to draw it through the curved nozzle. 



1 144 USE. 

Sand is taken from the elevated bin into the engine sand boxes through a 
pipe, the usual way. — Locomotive Engineering. 



Compressed air baths are the latest things in health restorers. 

One step further, and the fashionable cure will be taken in the Greathead 
compressed air shield at the "working face" of the newest Thames tunnel, wher- 
ever it happens to be. 

It is at Reichenhall, in the Bavarian highlands, that this newest invention 
is being applied to the cure of asthma, bronchial catarrh, and numerous . other 
forms of disease. The bath is constructed on very similar lines to the diving 
bell. The pneumatic chamber is built to accommodate from three to twenty 
persons, and can be either round or oval. The outside resembles more than any- 
thing else the turret of a modern man-of-war. Small windows with very thick 
glass panes let in the light, and the heavy iron door when closed is completely air- 
tight. The air admitted under pressure passed into a hollow space underneath 
the chamber and up through the carpet, which is placed over a perforated metal 
plate. This prevents any draught being felt, even when the pressure is at its 
greatest. The foul air is carried away by means of two pipes with openings imme- 
diately below the cover of the chamber. The inside is furnished with cane arm- 
chairs and a table, and the patients pass the time either in reading or writing, or 
very often in sleeping. 

Each sitting lasts about an hour and forty-five minutes; and during the 
first twenty-five minutes the pressure of the air is gradually raised by means of 
pumps till it attains 30 centimetres. This is maintained for forty-five minutes, 
and then the- normal pressure is gradually restored. The chief sensation during 
the sitting (says the Times in describing the process) is a slight pain and dis- 
comfort in the ears, but this soon passes off, and can, moreover, be greatly dimin- 
ished by filling the ears with cotton wool. For a beneficial and lasting result at 
least 30 sittings are required, and then a complete cure is very often effected. 

The idea was tried as long ago as 1832, but they did not succeed then in 
maintaining the purity of the air under pressure. 



After cleaning the iron work of the New York Viaduct at iSSth street, as 
described and illustrated in the "Cyclopedia of Compressed Air," the engineers in 
charge conducted a test of painting the cleaned surfaces by a compressed air paint- 
ing machine. It is necessary to paint the cleaned spaces very quickly on account 
of the rapidity with which the fresh surfaces oxidize. The Bryce Pneumatic 
Paint Machine was given a trial in which it was demonstrated that in twenty 
minutes it could cover 285 square feet, while it would require between three and 
four hours for one man to cover the same space by hand. The control of the 
machine was so good that the paint was distributed in the interior parts difficult 
to reach by hand, equally as well as the exposed surfaces. The overhead plates 
were painted without any dropping of the paint. One overhead opening between 



USE. 1 145 

adjacent plates was about half an inch wide and extended upward about two 
inches. This had to be painted formerly by means of a swab, but the interior sur- 
faces were coated by the air-blast without any trouble by moving the nozzle in 
front of the opening and about two feet from it. The construction of the paint 
distributor is very simple. The air and paint are conducted through separate 
passages to the base of the nozzle. The air passage ends in a small injector nozzle, 
adjustable longitudinally, which atomizes and sprays the paint into the main fa*n- 
shaped nozzle, and is discharged to the surfaces to be painted ; the operator at all 
times being able to regulate the quantity of paint discharged. 



An apparatus by means of which a railway guard can shut and lock all 
the doors in a train, by moving a lever in his van, has recently been tried on a 
train on the Metropolitan District Railway. This invention, which, we under- 
stand, has been at work successfully in Australia, and is known as the Fraser 
railway door controller, is actuated by compressed air, which can be supplied 
to cylinders fixed under the carriages. By a combination of pistons, rods, levers, 
and springs the doors can be made to shut, and this can all be done by the guard 
from his van, without his touching a single door. The action is said to be so 
gentle that, even if people's fingers get in the doors, these are only prevented from 
closing, and no injury results to the fingers. The apparatus, it is said, can be 
worked either by means of the air in the air-brake pipes, or by means of a sepa- 
rate air pump, or with modifications in connection with the vacuum brake. 



The employment of compressed air in hnishing silk ribbon is a branch ot 
compressed air application which has received little or no attention from com- 
pressed air authorities, but nevertheless air has been used quite extensively for 
this purpose and has proven of considerable value to the ribbon manufacturers. 
Compressed air is superior to steam for spraying the finishing material upon the 
ribbon, because its exhaust into the atmosphere is not offensive to the operator ; 
it does not scatter the particles of finishing material, but concentrates the entire 
force of the spray upon the ribbon. Ribbons finished with the compressed air 
spray possess a better lustre than those finished by the steam spray, because the 
steam condensation dilutes and weakens the finishing material. The air is heated 
before it reaches the spraying nozzles, in order to produce the desired effect. 



Experiments have recently been made with compressed air and compressed 
oxygen to purify the air in a long tunnel near Geneva, through which 200 trains 
pass every day. The compressed air is liberated from the cylinders on the engine. 
Tlie pure air blew back the smoke and clarified the almosphere. riic oxygen was 



IT46 



USE. 



allowed to escape into the fires of the engines, causing complete combustion and 
preventing the formation of dangerous gases, as well as making the air more 
wholesome by the addition of the oxygen. The compressed air was adopted 
because a cheaper method. This experiment suggests the feasibility of similar 
methods in running tunnels and possibly in the shafts and level workings of the 
mines. 



We present herewith the picture of a pneumatic hoist in use on the 1,400 
level of the Gwin mine, Calaveras County, Cal. This hoist has a drum with 
capacity to carry several hundred feet of suitable rope. The drum is operated 
by a small hand-wheel fastened to the centre of the shaft. The motor for oper- 




FIG. 498 — PNEUMATIC HOIST IN USE ON THE 1,400 LEVEL OF THE GWIN MINE, 
CALAVERAS CO., CAL. 

ating this hoist consists of two Dake engines of the reciprocating type and is 
operated by compressed air. It is portable and made so that it can be readily 
run through a drift on a flat car. 



The application of compressed air for mechanical purposes in Paris has 
developed to wonderful proportions. It is said that it now takes 24,000 horse 
power to operate all the appliances. These embrace printing presses, saws, pumps, 
grindstone lathes, sewing machines, tin-smith shears, ventilators, and enters into 
almost every industry. In 1892 they compressed 6,887 millions of cubic feet of 



USE. 1147 

air, with a system of 105 miles of compressed air pipe laid under the street, 41 
miles of which is used for pneumatic clock service, and about 64 miles for other 
appliances. 



At the Altoona shops of the Pennsylvania Railroad the problem of handling 
ashes from locomotives has been satisfactorily solved by the erection of several 
pneumatic ash-hoists. An iron frame resembling a gallows extends across three 
tracks. Under it there is an ash pit. The bottom of this pit has a narrow-gauge 
track on which small trucks run and carry what may be called bifurcated buckets 
to receive the ashes as they are removed from the ash-pans of the engines. The 
ashes are raked out of the ash-pan into these buckets. The buckets are then at- 
tached to the suspended hoist and run upon a trolley the length of the frame and 
dumped into a car. 



At the Globe Iron Works, Cleveland, O., a No. 5 Phoenix drill is being 
used for expanding the flues of a large marine boiler. This work is done by 
using the machine to drive an ordinary taper pin expander, and an idea of the 
rapidity with which the work can be accomplished by the use of the machine as 
stated may be had from the statement that on one boiler 280 3^" flues were ex- 
panded in ten hours; this time included all delays. The seams of the boiler are 
caulked with the Keller i}i" tool, built by C. H. Haeseler & Co., Philadelphia. 



Instead of blackening dry sand moulds by hand with a swab a compressed 
air sprayer is now used. It is easily handled and by its use the blackening is 
thrown into the pores of the sand and into the pockets and corners almost inac 
cessible with the swab. It is much quicker than the swab and the coating is 
more uniform. 



A correspondent of the National Engineer asks the following question : 
"Can you give me a rule to find the size of air compressor and pipes to 
operate an air lift to raise about 2,500 galg. of water per hour from a depth of 
300 ft.; the hole is 6-in. diam. and it is 100 ft. to the surface of the water; the 
water is lowered 25 ft. by pumping at the rate mentioned. j. t. b." 

This is the reply : 

"This well would require a s-in. casing and should be piped to twice the 
depth of the surface of the water from the top of the well when the water is at its 
lowest point, that is at twice 125, or 250 ft. The air pipe should be i-in. diam 
\n the well and the pipe between reservoir and well should be iJ^-J"- to I^^-in 
Steady pumping will depend on the air pipe and the casing being properly pro- 
portioned, for if the air pipe be too small, or the casing too large, the well will 
blow. It will be well to have ample reservoir capacity. Air supply to com- 



1 148 USE. 

pressor should be as cold as can be dbtained, for then the compressor capacity will 
be greater than with warmer air supply. The reservoir pressure should be about 
100 lbs. (250 X .434). The compressor should have a capacity of about one 
cubic foot of atmospheric air for each gallon of water to be raised." 



A discussion took place recently at the International Mining Congress at 
Brussels as to the limits of safety to which work can be carried on under com- 
pressed air. The Austrian doctors declared that men under twenty and over 
fifty years of age should not be allowed to work where the air pressure was high, 
and in all cases medical certificates should be forthcoming as to the soundness of 
the heart, lungs and the vascular system. An ear affection, a cold or gastric 
attack should be sufficient for prohibition. The limit of pressure should be sev- 
enty-five pounds, which would enable the work to be carried on under water at 
170 feet from the surface, but in such cases special precautions would be 
necessary in returning from the high pressure to the normal condition. The 
minimum would be 100 minutes, but the men may continue to work for any 
period. It is one of the peculiarities of working under high air pressure that 
healthy men might almost live in the pressure chamber, but the change from high 
to lower pressure should take one minute for every one and one-half pounds of 
pressure. Men acustomed to the work might take only ten minutes for a pres- 
sure of twenty-two pounds, fifteen minutes for thirty-seven pounds, or thirty 
minutes for a seventy-five-pound pressure. It is suggested that the men in pass- 
ing through the changes of pressure should suck sugar ; not that sugar possesses 
any particular virtue, but it insures the swallowing of the saliva and prevents 
the tympanum from being injured. As to the ventilation of the working cham- 
ber, the air should be renewed at the rate of 700 cubic feet per head per hour. — Ex. 



A correspondent asks : 

"It is desired to raise water from a well by the "Air-lift" process, the casing 
of same being 6" in diameter, and surface of water 80 feet below the ground. 
We wish to know if an ordinary 8" air brake pump can be used to accomplish this, 
it being necessary to convey the air a distance of 1,500 feet from the pump to the 
well. I presume it will be necessary to place a smaller pipe inside the casing for 
the purpose of raising the water. 

I should like very much to know what is the method of calculation for 
determining what amount of water, a given amount of compressed air, at a given 
pressure is capable of raising." 

The amount of water pumped by an Air Lift Pump depends upon the 
number of cubic feet of free air per minute, the height to which the water is 
raised above its surface and many other conditions under which the Air Lift 
Pump may operate. 

If your Air Brake Pump has 8'' x 8" cylinders and runs 120 strokes per 
mmute, the volume of free air compressed would be of course the product of the 



USE. 1 149 

piston speed by the area of the cylinder from which should be deducted perhaps 
20 per cent, for clearance and leakage with this style of pump. This will give 28 
— 20 per cent., say 22 cubic feet of free air per minute. 

The formula commonly used for determining the amount of water raised 
with a given amount of free air is as follows : 
G— 125A 

• where G equals the number of gallons per minute A equals cubic feet 

L 
of free air and L equals the lift in feet from the surface of the water to the point 

125x22 

of discharge. This would be for your case equals about 34 gallons per 

80 
minute. This applies only when the submergence equals one and one-half times 
the lift, or for your case 120 feet of water when lifting 80 feet above the water 
level, or to the surface of the ground only. As this water level will probably fall 
somewhat when pumping, the lift will be increased and the amo.int of winter 
pumped decreased accordingly. 

For a i" pipe line 1,500 feet long carrying about 22 cubic feet of free aii 
per minute, the loss of pressure by friction will be about 5 pounds — not an exces- 
sive amount. The water discharge pipe should be 2" and the air pipe ^'' or i". 
The air pressure will be about half a pound for each foot of submergence, being 
dependent upon the submergence and not upon the lift. 

While you can operate an Air Lift Pump by the use of an Air Brake Pump 
it is not an economical process. This style of pump uses from 150 to 250 pounds 
of steam per i horse power per hour, where an inexpensive belt driven Air Com- 
pressor would run on 40 pounds, and the saving in fuel would pay for the air com- 
pressor in a few months. It was recently brought out at a meeting of railroad 
officials, that if air brake pumps were to be had for nothing, it would pay better 
tc buy air compressors at an extravagantly high price on account of the fuel sav- 
ing. — Ed. 



A correspondent writes : 

1. How can I determine the amount of power that may be realized from a 
reservoir of known dimensions, charged with air at 225 pounds pressure? 

2. How can I determine the amount of power that it requires to compress 
this air? 

3. Why docs heat accumulate in a compressed air reservoir? 

4. Is there any book published which treats of the above subject in a sim- 
ple way? and if so, give title and publisher. 

[i. First determine the cubical contents of Receiver (cu. ft.) and multiply 
by 

(225 4- IS) = 16 
15 
Product will be = cu. ft. of free air in reservoir. 

All (lc])cnds upon the manner in which you arc going to use the air. Tf 
used in a motor, the cut-off is an important factor; and if air is reheated, the 
quantity consumed for a given power will be proportionately diminishecL 



II50 USE. 

We refer you to Table, page 117, Compressed Air, No. 8, Vol I., which will 
give you the consumption in free air for varying cut-off and for pressures up to 
150 lbs. For pressures up to 225 see general formula, page 69, Com pressed.. Air, 
No. 5, Vol. I. 

2. We refer you to any treatise on thermodynamics for a mathematical 
formula; or you will find in "Kent's" or "Haswell's" (64th edition) Pocket 
Books, a table of mean effective pressures for pressures up to 200 lbs., from 
which you can compute the horse power for any given case. 

3. The heat that accumulates in a compressed air reservoir is due to the 
heat of compression in the air cylinder — due to work done upon the air in com- 
pression. See Compressed Air, No. 3, Vol. I., page 14. 

4. Refer to Frank Richards' book. — Ed.] 



A correspondent writes : 

The following shows a simple method of calculating volumes of free air. 
It entirely obviates the tedious division by 14.7, and is correct. 

I shall be pleased if it is of any use, or worthy of a corner in your most 
interesting journal. 

To find the equivalent volume of free air corresponding to a given volume 
ot compressed air under any pressure — one atmosphere being = 14.7 lbs. per 
square inch. 

Volume ) Volume ) ,^ ^„ , , 

r . \ = • f X (0.068 p + i) 

free air ) comp. air ) ^ 

[. being the gauge pressure in lbs. per sq. inch. 

EX ^ ^TTl E. 

Find the equivalent in free air of 78 cu. ft. compressed air at 2,500 lbs. pres- 
sure per sq. inch. 

Free air = 78 j (o.' 68 X 2500) + i [ 

= 78 (i7'>+ I) 

= 13338 cubic feet. 



A correspondent writes: 

"Could you give me any advice or tell me if a triple expansion or a heavy 
duty Corliss engine can be run by compressed air the same as with steam? By 
answering the above, you will confer a favor." 

An engine operated by steam can be operated advantageously by com- 
pressed air, if such power is available. However, certain points must be taken 
into consideration. If a single cylinder engine is operated by compressed air, it 
is always advisable to reheat the air, say to 300 degrees at least, before utilizing 
the same. For a compound engine of any type, a reheater will be required to 
reheat the air before entering the high pressure cylinder, and as the air will lose 



USE. 1151 

a considerable amount of heat, on account of expansion in the high pressure 
cylinder, this loss of heat being proportional to the degree of expansion, a second 
reheater will be required between the high and low pressure cylinders, not only 
to increase the volume of air exhausted by the high pressure cylinder, but also in 
order to raise its temperature, as the final temperature of low pressure cylinders 
of compound engines, in many cases, would be below zero, and under such condi- 
tions proper lubricating could not be obtained. It would in no case be advisable 
to operate triple expansion steam engines by compressed air, as the low pres 
sure cylinder of a triple expansion engine derives its power almost entirely from 
the vacuum of the condenser, the mean effective pressure of a low pressure cyl- 
inder of a triple expansion engine being generally two or three pounds below 
the atmosphere, vacuum not taken into consideration. However, special triple 
expansion engines could be built to operate by compressed air, but a special 
ratio of cylinders would have to be established, and the initial air pressure to 
operate such an engine would have to be at least 300 pounds to the square inch, 
while no gain in economy would be obtained over the compound engine worked 
by air, provided the compound engine cylinders would be of such proportion as 
*o obtain an atmospheric terminal pressure in low pressure cylinder. 



A correspondent writes : 

I desire to submit the following questions to be answered through the col- 
umns of Compressed Air: 

First. — Is there any difficulty in transmitting compressed air and reheating 
it for power purposes? 

Second. — Does the back pressure from expansion in the reheater interfere 
with the flow of the air through the pipe leading to the reheater? 

Third. — Can compressed air be forced through a reheater at as low a 
pressure as from 30 to 45 pounds per square inch? 

Question 1. — Compressed air may easily be transmitted and reheated at the 
end of the line or at any point along the line for power purposes. This has been 
done for years past on large scales in Paris. Another case on a large scale is the 
transmission plant at the Chapin Mines, Quinnesec Falls, Mich. 

Another case is that of Jerome Park, N, Y., where a central plant is 
located and air transmitted in different directions and used for driving rock 
drills, pumps, etc. 

The difficulty in transmitting compressed air long distances arises only 
when large volumes of air are transmitted. In these cases the size of pipe and the 
nature of the country over which the pipe is to be laid must receive attention, and 
careful figuring only can determine whether it is best under certain conditions 
to transmit pneumatically or electrically. Electric transmission long distances and 
in large power units may be more easily and more economically installed where 
the nature of the country is rough and mountainous, and where the distance is 



II52 



USE. 



great, say from five to ten miles or more. In such cases it is visual to transmit 
electrically at high pressure, thus calling for a conduit of moderate dimensions 
and comparing favorably with the large compressed air pipes. The high-pressure 
electric current is reduced to low-pressure at the work. Compressed air, too, may 
be transmitted at high pressures and used, but this calls for extra heavy pipes and 
careful protection against leakages through expansion and contraction. Each 
case should be considered by itself, and a comparison of figures made, based on 
the conditions as they exist. 

Question II.— There is no back pressure due to reheating at the end of a 
pipe line. The reheater expands the air and causes a reduction in the velocity of 
flow from the compressor to the reheater. Each pipe line is proportioned in 
diameter of conduit to the velocity of flow, which is dependent on the volume 
and the pressure, thus a reheater used on the end of a line may admit of a smaller 
diameter of conduit because it thins out the compressed air, reducing its density, 
and as the pressure remains the same it practically enables the user to do more 
work with a definite given volume of compressed air at normal temperature. 

Question III. — Compressed air is not necessarily forced through a rehea'^'^; 
it passes through naturally, and at a velocity dependent on its pressure and upon 
the construction of the heater. These heaters as commonly constructed might do 
good work with compressed air at a pressure as low as ten pounds per square inch. 



A very practical and simple method of determining the quantity of air i 1 
by various pneumatic tools is followed by the United States Metallic Pack) ^ 
Company, of Philadelphia, Pa. A belt compressor is run at a fixed speed and as 
many tools of each size are connected on the compressor as it would maintain 
under the pressure shown in the column ; then taking the total capacity of the 
compressor and dividing by the number of tools attached to it, the result is ob- 
tained. The following table will show the result of a test recently made : 



NAME OF HAMMER. 


Size of 
Piston. 


Pressure. 


Cub. ft. of 

free air 
per minute. 


H. P. 

required. 


A. V ■ . . . 


Inches. 
13-16 


80 lbs. 
35-40 lbs. 
35-40 lbs. 
35-40 lbs. 

80 lbs. 


13 

8 

4 

3.57 
26 


1.70 


B.S 

C. S 


.75 
.3748 


D.S 


.3345 


Other tool about capacity of A. V 


3.40 



USE. 



1 153 



ALPHABETICAL LIST OF INVENTIONS. 



APPLIANCE. 



NAME OF INVENTOR. 



DATE OF ISSUE. 



NO. 



S. M. Laudis. . 

J. Grimm 

L. Chase 

L. Chase 

J. Griffin 

Andrews 

Barber 

Barnes et aL . . 

Bass 

Bass 

Bayley 

Bayley 

Beemer 

Beery 

Beery 

Bentley 

Bishop 

Boluss 

Boluss 

Boluss 

Boluss 

Borbridge et al 

Bothwell 

Boyden 

Boyden 

Bragg et al . . . . 
Brockway et al 
Brookmire .... 

Brown 

Buckpitt 

Burbanket al. 

Carpenter 

Carpenter 

Carpenter 

Catlett 

Chadwick 

Champion 

Christensen . . . 

Clark 

Clarke 

Clifton 

Clowry 

Coates 

Coates 

Collins 

Collins 

Conness 

Conness 

Corporan 

Corrington . 
Custer 



May 

Oct. 

Aug. 

Sept. 

Mar. 

June 

April 

Oct. 

Feb. 

Feb. 



14, 1867 
26, 1869 
12, 1873 
30, 1873 
I, 1859 

26, 1888 
4, 1893 

27, 1 89 1 
17, 188s 
22, 1887 



Feb. 17, 1891 



Nov. 

July 

May 

Nov. 

Jan. 

Dec. 

May 

Feb. 

Oct. 

Sept. 

Sept. 

July 

May 

May 

Nov. 

Sept. 

April 

May 

Sept. 

May 

Mar. 

Feb. 

July 

Jan. 

Aug. 

Feb.- 

Feb. 

July 

Nov. 

Dec. 

June 

Feb. 

Feb. 

April 

April 

June 

Aug. 

Oct. 

Nov. 

Jan. 



6, 1894 

28, 1896 
12, 1891 

1, 1892 
5, 1897 

25, 1894 
15^ 1888 
19,^1889 

29, 1^89 

2, i8>5^o 

18, 1894 

21, 1891 
25, 1897 

25, 1897 
9,1897 

19, 1882 
21, 1896 

22, 1894 

14, 1897 
20, 1890 
22, 1887 
28, 1888 

26, 1892 

25, 1898 

1, 1876 

3, 1874 

26, 1895 
10, 1894 
12, 1895 
18, 1894 

7, 1898 
2, 1892 
2, 1892 
2,1889 
2, 1889 

4, 1895 
3.1897 
4.1892 

30, 1897 
21, 1896 



64,677 
96,223 
141,762 
143,329 
23,084 
385,224 
494,772 
462,193 
312,245 
358,142 

Reissue 

II.I45 
528,712 
564,863 
452,334 
485,365 
574,656 
531,584 
382,749 
398,310 
414,138 
435,791 
526,178 
456,247 
583,278 
583,279 
593,531 
264,617 
558,670 
520,391 
589.957 
428,299 

359.953 
378,657 
479,736 
598,814 
180,460 
147,225 
534.813 
522,825 
549,703 
531,100 

605.394 
467,920 
467.921 
400,638 
400,639 
540,539 
587.519 
483.802 
594.464 
553.481 



1154 



USE. 



APPLIANCE. 



Air Brake. 



r 




NAME OF INVENTOR. 



Custer Jan. 

Daellenbach Nov. 

Daelleirbach Dec. 

Dean Dec. 

L. H. Develley Nov. 

Dickson Oct. 

Dixon May 

Dixon Sept. 

Dixon April 

Dixon I Oct. 

Dixon j Dec. 

Dodd iNov. 

Dunn j April 

Dunn j Jan. 

Dunn } Sept. 

Dunn Jan. 



DATE OF ISSUE. 



Dunn . . 
Dunn . . 
Duval . . 
Duval . . 
Duval . . 
Dwelly . 
Eames . . 
Eames . . 
Easton . , 
Edwards 
Eldridge 
Erdody . 
Fahrney 



Feruley et al Jan. 

Nov. 
April 
Nov. 
Nov. 
jMay 
[May 

bet. 



Fish 

Flad 

Flad 

Flad 

Fogelberg . . . 
C. Fogelberg. 
Ford 



Sept. 

Feb. 

Nov. 

Dec. 

Dec. 

Nov. 

May 

May 

Dec. 

Oct. 

Oct. 

Dec. 

Nov. 



Fox 

Fox 

Fox 

French . . . . 
Genett .... 

Glass 

Glenn ...... 

Goode 

Graebing . . 

Gray 

Green et al. 

Green 

Guels 

Guels 

juels 

Guillemet .. 



Dec. 
Dec. 
Dec. 
Jan. 
Mar. 
Dct. 
Nov. 
STov. 
Dct. 
Feb. 
Dec. 
Dec. 
June 
June 

. ^pril 

5ept. 



21, 1896 
12, 1889 

2, 1890 
19, 1893 
28, 1865 

7, 1884 

1. 1888 

18. 1888 

30. 1889 

1. 1889 
31, 1889 

10. 1891 

19. 1892 
10, 1893 

17. 1895 

28. 1896 
1, 1896 

n, 1897 
22, 1892 

12. 1893 
12, 1893 
28, 1865 
10, 1881 

10. 1881 
7, 1886 

23. 1894 
9, 1894 

12, 1893 

1, 1892 

21, 1896 

23. 1897 
8, 1884 
4, 1884 
4, 1884 

28, 1872 
28, 1872 

31. 1882 



Ford ■ Mar. 27,1 



553,482 
415,162 
442,019 
511,071 
51,158 
306,140 
382,031 
389,643 
402,418 
412,168 
418,506 
462,966 
473,302 
489,527 
546,510 
553,517 
56-^0.24 

S7/,'H25 
486,703 
510,635 
510,870 
51,158 
241,323 
241,325 
354,014 
527,838 
527,327 
510,594 
485,182 
553,498 
593,996 
296,546 
1307,535 
1307,536 
127,332 
p7,332 
^v.6,684 



JjRei 



18, 


1894 




18, 1894 




18, 1894 


1.70 
.75 


29, 


1895 


.3748 


24, 

20, 


i89( 
189^ • 


.3345 
J.40 


9, 


188- 


_ 


30, 


188 




20, 


i8c 




22, 


i& 




II, 


18 




30, 


iF 




19, 


I 




19, 


J 





15, 
30, 






USE. 



1155 



APPLIANCE. 



NAME OF INVENTOR. 



DATE OF ISSUE. 



NO. 



« * 



Guillemet , . . . 
Guillemet . . . . 
Guillemet . . . . 

Gunckel 

Gunckel 

Haberkorn . . . 
Haberkorn . . . 
Haberkorn . . . 
Haberkorn . . . 

Hall 

Hall 

Hamar et al . . 

Hanney 

Hanscom .... 
Hanscom .... 
Hanscom .... 

Harris 

Harris 

Harris 

Harris 

Harris 

Harris 

Harris 

Harvey 

Hayden 

Hay den 

Herbert 

Herder 

Higgins 

High 

Hinckley 

Hogan 

Hogan 

Hogan 

Hogan 

Hogan 

Hogan 

Hogan 

Hogan 

Hogan 

Hogan 

Hogan 

Holleman . . . 

Hollerith 

Hollerith 

Hollerith .... 

Hopper 

Hopper 

Hopper 

Howe et al, . . 
Humbert et al 

Hunt 

Hunt 

Hunt 

James 

James 



Sept. 

Nov. 

Nov. 

May 

Mar. 

Feb. 

Mar. 

Oct. 

Dec. 

Aug. 

Dec. 

Mar. 

June 

Oct. 

Sept. 

Aug. 

Dec. 

April 

Feb. 

Mar. 

Aug. 

Oct. 

Nov. 

Feb. 

Aug. 

Dec. 

Nov. 

April 

Aug. 

Mar. 

Nov. 

July 

Aug. 

Aug. 

Mar. 

April 

Sept. 

Sept. 

Sept. 

Dec. 

Dec. 

Jan. 

June 

Jan. 

Jan. 

Jan. 

July 

June 

Sept. 

Sept. 

May 

Nov. 

Aug. 

Mav 

July 

Feb. 



6,1892 
10, 1896 

10, 1896 

11, 1897 
29, 1898 

2,1886 

5,1889 

22, 1889 

18, 1894 

17, 1880 

29, 1896 
IS 1898 
14, 1892 
10, 1882 
22, 1885 

30, 1887 

16, 1890 
5,1892 

20, 1894 

13, 1894 
6,1895 
1,1895 

17, 1896 
21, 1888 

30. 1892 

5,1893 
24, 1896 

14, 1896 
8, 1893 
3,1896 

14. 1893 
29, 1890 

5, 1890 

5, 1890 

3, 1891 
26, 1892 

6, 1892 
17, 1895 
17, 1895 
17, 1895 
24, 1895 

5,1897 
25,1889 

12, 1886 
12, 1886 
12, 1886 
14, 1885 

ID, 1890 
I, 1891 

8, 1896 

21, 1895 

13. 1894 
V. 1895 

4. 1897 

6. 1875 
24, 1 89 1 



482,040 
571,115 
571,116 
582,391 
601,253 
335,446 
398,829 
413,253 
531,181 
231,311 
574,062 
600,641 
476,880 
265,671 
326,646 

369,057 
442,621 
472,190 
515,220 
516,202 
544,253 
547,253 
571,662 
378,365 
481,651 
509,898 
572,009 

558,174 
503,083 
555,809 
508,421 
433,127 
433,594 
433,595 
447,731 
473,839 
482,058 
546,448 
546,449 
551-440 
551,767 
574,866 

405.705 
334,020 
334-021 
334,022 
321,971 
430.024 
458,626 
567,476 
539.430 
529,270 
545,295 
581,912 
165,235 
447,236 



1 156 



USE. 



APPLIANCE. 



NAME OF INVENTOR. 



DATE OF ISSUE. 



Air Brake. 



James 

James 

Jeffries 

Jeffries 

Jones 

Juul 

Keywood . . . . 
Kholodkowski 

Knapp 

Kneeland . . . . 
Knudsen .... 
Knudsen .... 

Ladd 

Lansberg 

Lansberg . . . . 
Lansberg . , . . 
Lansberg . . . . 
Lansberg . . . . 
Lansberg . . . . 
Lansberg . . . . 
Lansberg . . . . 
Lansberg .... 
Lansberg . . . . 

Lapish , 

Lee 

Lee 

Lee 

Lee 

Lee 

Lehy 

Lencke et aL . 

Lencke 

Lewis 

Lewis 

Lindsey 

Lorraine 

Loughridge . . 

Luce 

T. Luce 

Mable 

Mable 

Magowan .... 

Maher 

Marble 

Mark 

Marsh 

Marshall 

Marshal] 

Martin 

Massey 

Massey 

Massey 

Massey 

Massey 

Massey 

Masterman . . . 



Oct. 

Aug. 

Jan. 

Nov. 

Aug. 

Nov. 

July 

Mar. 

June 

Oct. 

Feb. 

Sept. 

July 

July 

Nov. 

Nov. 

Nov. 

Nov. 

Nov. 

Nov. 

Oct. 

Feb. 

Mar. 

Mar. 

Mar. 

Mar. 

Mar. 

Mar. 

Mar. 

April 

April 

April 

May 

Sept. 

June 

Aug. 

Nov. 

Sept. 

Sept. 

Sept. 

Dec. 

Feb. 

Aug. 

Oct. 

Nov. 

Jan. 

July 

May 

Sept. 

Nov. 

Mar. 

April 

July 

Mar. 

April 

Aug. 



13, 1891 
21, 1894 

23, 1894 
26, 1895 

3, 1875 
3,1896 

4, 1893 
15, 1898 

4, 1878 
26, 1886 
9, 1892 
4, 1894 
6, 1875 

24, 1888 

13. 1888 

19. 1889 
19, 1889 
19, 1889 
19, 1889 

19, 1889 

28, 1890 
3,1891 

20, 1894 
12, 1889 
31, 1896 
31, 1896 
31, 1896 
31, 1896 
31, 1896 

17, 1888 
10, 1894 
10, 1894 

29, 1888 

3, 1889 
9, 1896 

23. 1881 

9, 1880 

10, 1872 

10, 1872 

18, 1894 
8, 1896 

12, 1884 
5,1890 

11, 1892 
4, 1884 

15. 1889 
21, 1891 
26, 1896 

30. 1890 

12, 1889 

10. 1891 
28, 1891 

4. 1893 

19, 1895 
9,1895 

29, 1893 



USE. 



1157 



APPLIANCE. 



NAME OF INVENTOR. 



DATE OF ISSUE. 



Maxwell 

Maxwell 

McAvoy 

H. L. McAvoy. 

McCarty 

Mcintosh 

McKinney . . . . 

McNulta 

Melson 

Mills 

Mills 

Moschcowitz . . 

Nef 

Nellis et al. .. 

Newton 

Norris 



Noyes 

Noyes 

Noyes 

Noyes 

Noyes 

Noyes 

O'Hara 

Olin 

Omick 

Omick 

Osgood 

Paradise 

Park 

Park 

Park 

Park 

Park 

Park 

Parke et al . . . 

Pelton 

Perkins 

Perkins 

Perrine 

Perrine 

Perrine 

Perrine 

Pettengell 

Pickering .... 

Pinkston 

Pool et al 

Prince 

Pritchard et al 
Pritchard et al, 

Pritchard 

Raoul 

Redfern 

Reilly 

ReniflF 

Reyburn 

Richardson . . . 



Aug. 

June 

April 

April 

Nov. 

Aug. 

Jan. 

Mar. 

Nov. 

June 

April 

Aug. 

April 

Nov. 

April 

Oct. 

Jan. 

July 

Nov. 

Nov. 

Feb. 

Feb. 

May 

Feb. 

July 

Aug. 

Mar. 

Feb. 

June 

Dec. 

July 
June 
June 
June 

Oct. 

Sept. 
July 

Feb. 

Aug. 

Aug. 

Aug. 

Nov. 

Jan. 

Jan. 

July 

June 

June 

Mar. 

Mar. 

Sept. 

May 

June 

Dec. 

Oct. 

Oct. 

Jan. 



20, 1878 
25, 1889 
29, 1873 
29, 1873 
13, 1894 
31, 1897 
27, 1885 
29, 1892 
23,1886 

7, 1892 
16, 1894 

27, 187s 

12, 1898 

23, 1897 
16, 1878 
22, 1889 

28, 1896 

21, 1896 
10, 1896 

10, 1896 
2.2, 1898 

22, 1898 
8,1894 
8,1898 
7,1896 

24, 1897 
4, 1879 

19, 1884 
26, 1888 

4, 1888 
23,1889 

9, 1896 
21, 1898 
21, 1898 

3,1893 

13, 1892 
13, 1886 

8,1898 
3, 1875 
3, 187s 
3, 1875 
2, 1875 

11, 1898 
19, 1886 
11,1893 

13, 1893 
18, 1878 

5,1889 

5,1889 

10, 1889 

14, 1878 

15, 1897 
18, 1883 
10, 1876 

6, 1896 
23, 1894 



207,126 
405,968 
138,339 
138,339 
529,290 
589,265 
311. 196 
471,801 
352,927 
476,546 
537,784 
166,026 
602,094 
594,033 
202,368 
413,205 
553,565 
564,389 
571,095 
571,786 
599,348 
599,349 
519,681 
598,678 
563,612 

588,913 
212,972 

293.774 
385,198 
393,784 
407,445 
561,811 
605,904 
605,905 
506,185 
482,382 
345,537 
598,887 
166,404 
166,405 
166,400 

169.575 
597,220 
334,466 
501,359 
499,582 
204,914 
399,157 
399,158 
410,922 
203,647 
584,705 
290.269 
183.206 
568.923 
513,145 



1 158 



USE. 



APPLIANCE. 



NAME OF INVENTOR. 



DATE OF ISSUE. 



Air Brake. 



Riggs 

Roberts 

Robinson . . . 
Rogers et al. 
Rothschild . . 
Rothschild . . 

Rymer 

Schenck .... 
Schenck .... 
Schenck .... 
Schroyer .. . . 

Schuitz 

Sennett et al. 
Sennett et al. 
Shallenberger 
Shearwood . 
Shortridge . 

Shortt 

Shortt 

Shortt 

Shortt et al. 

Shortt 

Shortt 

Shortt 

Silcock 

Sjogren 

Slater 

Sloan 

Sloan 

Sloan 

Solano 

Solano 

Solano 

Solano 

Solano 

Solano 

Steedman . . . 

Steger 

Stevens 

Stewart 

Stewart .... 
Thayer et al. 
Thompson . . 
Thompson . . 
Tower et al. 

Trapp 

Trott 

Van Dusen . . 
Voorhees . . . 
Voorhees . . . 

Waite 

Walker 

Walker et al. 

Wands 

Ward 

T. O. Ward. 



Aug. 

July 

Oct. 

Jan. 

Feb. 

Feb. 

Dec. 

Aug. 

Dec. 

Jan. 

April 

Sept. 

Jan. 

Mar. 

Oct. 

Jan. 

Mar. 

Feb. 

Dec. 

April 

April 

April 

April 

April 

Feb. 

June 

May 

Oct. 

Sept. 

Nov. 

Jan. 

Feb. 

May 

July 

June 

June 

July 

Aug. 

May 

Jan. 

Mar. 

Aug. 

Sept. 

Nov. 

April 

July 

Mar. 

Dec. 

Aug. 

Sept. 

Nov. 

Oct. 

Oct. 

May 

Jan. 

Jan. 



4,1891 

29, 1890 
7,1890 

21, 1896 

27, 1894 

2-], 1894 

10, 1889 
7, 1894 

18, 1894 

22, 1895 
22, 1890 

30, 1879 

10, 1893 

19, 1895 
17, 1893 

5, 1897 

2, 1897 
16, 1892 

11, 1894 
30, 1895 
30, 1895 
30, 1895 
30, 1895 

30, 1895 
9,1892 
17,1884 

26, 1891 

28, 1884 

29, 1885 

10, 1885 

24, 1888 

28, 1888 
8,1888 

31, 1888 

25, 1889 

25, 1889 

16, 1895 

11, 1874 

29, 1877 
28,1890 

27, 1894 
21, 1883 

3, 1895 

17, 1896 

30, 189s 
6, 1897 

19, 1895 

26, 1882 

7,1894 
II, 1894 
10, 1891 

7, 1890 
13, 1896 
17, 1898 
30, 1872 
30, 1872 



USE. 



1 159 



APPLIANCE. 



Air Brake. 



and Signal. 



Air Chamber... 
Air Compressor 



NAME OF INVENTOR. 



Wessels et al 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse et al, 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse 

Westinghouse et al 

Westinghouse 

Westinghouse et al 
G. Westinghouse. , 
G. Westinghouse.. 
G. Westinghouse. , 
G. Westinghouse.. 

Wheeler 

White 

Willets 

Williams 

Williams 

Williams 

Williams 

Williams 

Williams 

Willis 

Willson 

Winters 

Wisner 

Wisner 

Zenke 

R. Creuzbaur 

Allen 

Allen 

Allen 

W. Arthur 

Avery 

B. T. Babbitt 

B. T. Babbitt 

Babbitt 

Babcock 

Babcock 

Babcock 

Babcock 

Bailey 

Baker 



DATE OF ISSUE. 



Oct. 

April 

Jan. 

Mar. 

Mar. 

Oct. 

Oct. 

April 

April 

July 

April 

June 

Aug. 

Aug. 

Jan. 

Mar. 

Feb. 

Mar. 

Oct. 

Mar. 

Oct. 

Jan. 

Mar. 

Mar. 

Oct. 

Sept. 

April 

June 

Dec. 

July 

July 

July 



22, 1895 
13, 1869 

23. 1872 
S, 1872 
5, 1872 

28. 1873 

27. 1874 

27. 1875 
II, 1876 
25, 1786 
22, 1879 

28, 1881 
2,1881 
2, 1581 
9, 1883 

29, 1887 
18, 1890 
24, 1891 
20, 1891 
3i> 1896 
26, 1897 

23, 1872 
5, 1872 
5, 1872 

28, 1873 

24, 1895 
23, 189s 

2,1896 
4,1888 
I, 1890 
I, 1890 
8,1890 



Nov. 18, 1890 



Nov. 

Aug. 

Mar. 

Nov. 

Jan. 

Feb. 

Nov. 

June 

Feb. 

Feb. 

May 

July 

Sept. 

May 

Nov. 

Dec. 

Feb. 

July 

Oct. 

July 

Mar. 

June 



25,1890 
19, 1884 
20, 1894 
23, 1897 
26, 1886 

24. 1891 
17, 1896 
18, 1801 

8, 1881 

8, 1881 

27, 1884 

25, 1865 

20. 1892 
17, 1870 
12, 1872 
II, 1877 
21, 1882 
10, 1883 
23, 1883 
17, 1894 

23, 1875 
20, 1882 



NO. 



548,335 

88,929 

123,067 

124,404 

124,405 
144,005 

156,323 
162,465 
175,886 

180,179 
214,603 

243,415 
245,109 
245,110 
270,528 
360,070 
421,641 
448,827 
461,779 
557464 
592,461 
123,067 
124,404 
124,405 
144,005 
546,835 
538,002 
561,301 
393,950 
431,303 
431,304 
431,790 
j Reissue 
I 11,124 
441,526 
303,777 
516,692 
594,228 
335,094 
446,908 
571,736 

32,595 
237,359 
237,360 
299.314 

48,886 

482,775 
103,121 
133,004 
198,067 
253,830 
280,997 
287,358 
523,064 
161,090 
259,741 



ii6o 



USE. 



APPLIANCE. 



^AME OF INVENTOR. 



DATE OF ISSUE. 



Air Compressor. 



Beck 

Beers 

Bennett 

Bicknell 

Birner & Messing. 

Blake 

Boerner , 

Bois , 

Bois 

Bolton 

Bradley 

Brislin 

Brotherhood 

Buell 

Buell 

Zarobbi & Bellini. , 

hamberlain 

hamp 



hamp 

hamp 

3hamp 

3hamp 

hamp 

Dhamp 

3hamp 

hamp 

haquette 

haquette 

hase 

hichester . . . . , 
"hichester .... 
"hichester . . . . , 

lark 

lark 

Clayton , 

layton 

Clayton 

layton 

I!layton 

onnor & Dods. 



orey 

rabtree . . . . 

rocker . . . . 

ullen 

ullingworth 

ullingworth 

ullingworth 

ummings . 

ummings . . 

ushier .... 

Davey 

Dean 

Deeds 

DeLaval . . . . 
Depp 



Dillenburg 



June 

Dec. 

Aug. 

Feb. 

May 

Feb. 

Mar. 

May 

Tune 

Mar. 

Mar. 

Aug. 

Feb. 

Nov. 

Sept. 

Jan. 

Jan. 

Jan. 

Feb. 

July 

A.ug. 

A.ug. 

A.ug. 

^ug. 

Oct. 

Nov. 

Oct. 

A-ug. 

June 

Nov. 

Jan. 

Sept. 

June 

April 

Jan. 

Sept. 

Nov. 

May 

Feb. 

Oct. 

Jan. 

Nov. 

May 

Nov. 

Oct. 

Dec. 

Feb. 

May 

Oct. 

Mar. 

Aug. 

Mar. 

June 

Dec. 

Jan. 

A.ug. 



7, 1892 
12, 1882 

28, 1883 
27, 1883 
29, 1894 

12, 1895 

29, 1881 

25, 1880 
20, 1882 
24, 1885 
14, 1882 

5, 1884 
20, 1894 
23, 1880 

6, 1881 

26, 1875 

10, 1888 

30, 1894 

27, 1894 

31, 1894 

13, 1895 
13, 1895 
13, 1895 

13, 1895 

15, 1895 
3,1896 

29, 1895 

11, 1896 
9, 1874 

18, 1884 

12, 1886 
27, 1887 

2, 1891 

14, 1896 

16, 1877 
30, 1879 
25, 1879 
24, 1881 

26, 1895 
5,1880 

20, 1885 

30, 1897 
2, 1876 

4, 1884 

23, 1883 
28, 1886 

7, 1888 

24, 1887 
8,1889 

25, 1881 

27, 1889 
27, 1888 
30, 1874 

19, 1893 
5, 1886 

30, 1892 



^76,723 
: 568,854 
283,955 
73,014 
520,405 
134,192 
239,310 
227,877 
259,799 
514,218 

254,915 
502,978 
, 515,282 

234,751 
246,657 

59,075 
576,141 
513,556 
515,516 
523,830 
544,456 
544,457 
544,458 
544,459 
547,768 
570,540 
548,800 
565,429 
[51,753 
508,061 

533,994 
570,376 
453,374 
558,041 
[86,306 

>20,I23 
222,014 
241,930 
534,814 
232,939 
511,106 
, 594,524 
76,931 
507,442 
287,104 

555,002 
577,481 
563,509 
, ^12,474 
236,992 
t09,773 
580,195 
t52,468 
511,086 
B33,6i3 
681,850 



USE. 



1161 



APPLIANCE. 



NAME OF INVENTOR. 



DATE OF ISSUE. 



NO. 



Air Compressor. 



Doremus 

Dow , 

Dreyfus 

DuFaur , 

Duffy 

F. S. Dumont. . 

Dunn 

Durand 

Dyer 

Eckart 

Ehlers 

Elliott 

Ellis 

Eloheimo 

G. D. Emerson. 

J. Ericsson 

Erwin 



Erwin , 

Erwin 

Erwin , 

Farrell 

Fasoldt 

Fauntleroy 

Fevrot 

Fitzpatrick 

Fitzpatrick 

Flindall 

Flood 

Fogg 

Forster 

Forster 

Forster 

Fox , 

Fox 

Fox 

Freeman 

Freeman , 

Frizell 

Fulton , 

Funk 

Gardner 

Garrison 

Githens 

Griffiths et al 

Griffiths et al 

G.iffiths et al 

Guillemet 

Gustafson 

Guthrie 

Guyser 

Haines 

Haines 

Hanford 

Hanston & Burdan, 

Harrold 

Harvey 



Sept. 

May 

Mar. 

June 

Dct. 

April 

April 

Nov. 

June 

Feb. 

July 

Sept. 

Feb. 

Aug. 

Aug. 

Dec. 

Oct. 

Dec. 

April 

May 

July 

Aug. 

April 

Feb. 

Mar. 

April 

July 

May 

Mar. 

Jan. 

Jan. 

June 

Sept. 

June 

Fune 

Mar. 

Dec. 

Jan. 

May 

Dec. 

Nov. 

Jan. 

Tuly 

Dec. 

3ct. 

Feb. 

5ept. 

Nov. 

Dec. 

May 

Mar. 

Aug. 

May 

Mar. 

July 

Jan. 



10, 1878 
4,1886 
5, 1878 
2, 1896 

1,1895 
27, 1869 
19, 1892 

19, 1895 
22, 1897 

3,1880 
I, 1884 

29, 1896 

17, 1874 

26, 1890 

20, 1872 

30, 1873 

27, 1885 
29,1885 

20, 1886 
15,1888 
19, 1892 

23, 1892 

28, 1874 
16,1886 

I, 1881 

30,1889 

6,1897 

8,1894 

14, 1893 
3,1888 

17,1888 
12, 1888 
25, 1883 
30, 1885 
30, 1885 

1. 1881 
25, 1883 

29, 1878 
16, 1876 

24, 1889 

18, 1879 
16, 1877 

7, 1896 
4, 1894 

15, 1895 
2,1897 
6,1892 

21, 1893 
17,1889 
26,1896 
15, 1892 

2, 1892 
3.1892 

29, 1892 
20,1886 
21, 1879 



1207,954 
341,099 
200,901 
561,160 
547,338 
! 89,390 
,1473,302 
550,163 
585,090 
224,081 
301,348 
568,433 
147.623 
435.034 
130,627 

146,055 
329,377 
333,208 
340,496 
382,760 
479,260 
481,527 
1150,312 
1336,224 

p38,374 
ko2,5i7 

585,955 
1519,383 
1493,263 

1375,929 
§76,589 
384,356 
285,743 
321,206 
321,207 
238,225 
290,764 
199,819 
177,495 
417.717 
221,802 
186,336 
563,477 
530,335 
547,882 

576,364 
482,040 
509,220 
417.482 
560,987 
470,934 
480,193 
474.296 
471,766 
345.969 
211,570 



Il62 



USE. 



APPLIANCE. 



Air Compressor. 



NAME OF INVENTOR. 



Henderson &Schultz 

Hill 

Hill 

Hill 

Hill 

Hill 

Hill 

Hill 

Hill 

Hill 

Hill 

Hill 

Hill 

Hill 

Hill 

Hill 

Hill 

Honigmann 

Hudson 

Hugentobler 

Hunter 

Hutchinson 

Jackson 



Johnson 

Johnston 

Johnston 

Kalthoff 

Keenan 

Keenan 

Knight 

Knoche 

Krutsch 

Laurence 

Lawler 

Lawrence et al . . . 

Leavitt 

Liming 

Livingston 

Lowe & Guyser. 

Manning 

Manz 

Massey 

Mayrhofer 

Mayrhofer 

McKim 

McLean 

Merritt 

Middleton 

J. B. Mignon. .. 

Miles 

Monson 

Monson 

Moore 

Moore 

Moore 

Moyer 



DATE OF ISSUE. 



May 

Jan. 

July 

Feb. 

June 

July 

July 

July 

July 

Feb. 

Mar. 

Nov. 

May 

June 

Nov. 

Nov. 

Nov. 

Nov. 

May 

June 

Nov. 

Aug. 

July 

Sept. 

Jan. 

Nov. 

Dec. 

June 

Oct. 

July 

Nov. 

July 

Jan. 

Feb. 

April 

June 

Oct. 

May 

Feb. 

April 

May 

Aug. 

Jan. 

July 

Jan. 

May 

June 

Sept. 

Mar. 

Oct. 

May 

Oct. 

June 

Sept. 

Dec. 

July 



17, 1892 

4, 1876 

13, 1880 

1, 1881 
21, 1881 
12, 1881 
12, 1881 
25, 1882 
25, 1882 

5,1884 
24, 1891 

4,1891 

12, 1891 

23, 1891 
17, 1891 

24, 1896 
2,1897 

13, 1883 
24, 1881 

1,1886 
13, 1888 

16, 1892 
29, 1879 

21, 1880 
27, 1874 

4, 1879 

17, 1895 
12, 1888 

8, 1895 
13, 1897 

7,1893 
15, 1884 
25, 1876 
20, 1883 
27, 1880 

23, 1885 
20, 1896 

24, 1881 

19, 1895 

11, 1882 
2, 1876 

12, 1890 

18, 1881 

25, 1882 
3, 1888 

II, 1886 
23, 1896 

22, 1874 

19, 1867 

5,1897 
16, 1882 

20, 1885 
3, 1879 

18, 1883 

23, 1884 

2, 1895 



USE. 



1 163 



APPLIANCE. 



NAME OF INVENTOR. 



DATE OF ISSUE. 



NO. 



Air Compressor. 



Nichols 

Nichols 

Noack , 

Nordberg 

Norris 

North 

Nosbaume 

Noyes , 

O'Brien 

Overton 

Overton 

R. S. Pardee 

Parkinson 

J. S. Patric 

J. S. Patric 

Pedrick 

Pendleton 

Perine 

Perry 

Perry 

Pfanne 

Phillips 

Pitchford 

Pitchford 

Pitt 

Quast 

Quinn 

Rand 

Rand & Halsey.... 

Reynolds 

Reynolds 

Reynolds 

Reynolds 

Reynolds 

Reynolds 

Richards 

Richmann 

Richmann 

Richmann 

Rix 

Rix 

Roberts 

Robinson & Kiser. . 

Root 

Sawtell 

Schutzinger 

Schutz & Henderson 

Seal 

Seal 

Sergeant 

Sergeant 

Sergeant 

Sergeant 

Sergeant 

Sergeant 

Sergeant 



Feb. 

Aug. 

Nov. 

Sept. 

Dec. 

Oct. 

Nov. 

July 

June 

Aug. 

Aug. 

Oct. 

April 

Oct. 

Mar. 

Aug. 

June 

April 

Nov. 

June 

Mar. 

May 

May 

Oct. 

July 

July 

Jan. 

Mar. 

Feb. 

Mar. 

Feb. 

Aug. 

Feb. 

Feb. 

Dec. 

Nov. 

June 

Sept. 

Nov. 

Dec. 

Dec. 

Dec. 

Oct. 

Oct. 

Oct. 

Nov. 

April 

Mar. 

Sept. 

Nov. 

Sept. 

Nov. 

Mar. 

July 

Feb. 

Dec. 



25. 1896 

31. 1897 

26. 1895 
I, 1891 

30, 1884 

9, 1894 

20, 1888 

14. 1896 
21, 1892 
22, 1882 
22, 1882 

14, 1873 
18, 1865 
17, 1871 

2, 1880 
13, 1895 

2,1896 

13. 1897 
8,1892 
6, 1893 

25, 1884 
12, 1891 
20, 1879 

19, 1880 
10, 1888 

4, 1893 
II, 1881 
21, 1882 

18, 1890 
16, 1875 
27, 1877 

1,1882 

20, 1883 
21,1888 

I, 1896 

10, 1891 
29,1880 

15, 1891 
3, 1891 
7, 1880 

21,1880 
I, 1896 

11, 1881 

16, 1877 
24, 1876 

7, 1893 

3, 1894 

14, 1876 

19, 1876 
2,1880 

19, 1882 
26, 1889 
ID, 1891 

21, 1891 
13, 1894 
II, 1894 



555,178 
589,190 
550,352 
45H.975 
310.148 
527,248 
393,i7-> 
563.794 
477,381 
263,206 
263,207 

143,634 
47,328 
120,094 
225,151 
544,548 
561,126 

580,714 
485,881 
498.989 
295.800 
452,283 
215,540 
233.432 
386,028 
501,046 
226,455 
255,116 
421,611 
160,956 
187,906 
262,119 
272,771 
378,336 
572,377 
462,776 
229,468 
459.527 
462,453 
235.296 
235,816 

572,314 
248,218 
196,253 
183,596 
508,150 
517,628 
174,860 
182,333 
233,881 

264,775 
415,822 
447,910 
456,165 

514,839 
530,662 



ii64 



USE. 



APPLIANCE. 



Air Compressor. 



Air Condenser. 



Air Cooler and Ice Manufacturer. 



Air Cushion, 
Air Draft... 
Air Engine , 



NAME OF INVENTOR. 



Sergeant 

Sergeant 

Shaw 

Shedlock 

Sherman 

Smith 

Smith 

Spencer 

Spencer 

Springer 

Stambaugh 

Stockman 

Strange 

Sturgeon 

Sturgeon 

Swartz 

Tallman 

Tatham 

Taylor 

Taylor . ; 

Taylor 

Teal 

Thomas 

Thomas 

Toennes 

Treat 

Underwood 

Walker 

Wang ■. 

Wang 

Wang 

J. B. Waring 

H. J. Bailey 

J. Cochrane 

H. Moore 

J. S. Patric 

E. H. Grant 

T. D. Kingan 

J. Kraffert 

N. S. Shaler 

F. Villard 

J. W. Wetmore. . . . 

S. Randall 

Allen 

W. Alworth 

Anderson 

And'son&Ericksson 

J. B. Atwater 

Babcock 

Babcock 

Babcock 

Bair 

Baldwin 

Baldwin 

Baldwin & Bradford 
Barbour & Hansen. 



DATE OF ISSUE. 



Oct. 

Mar. 

Jan. 

July 

May 

Dec. 

Dec. 

April 

Aug. 

Dec. 

Oct. 

Nov. 

Nov. 

Aug. 

April 

May 

April 

Dec. 

July 

July 

July 

May 

July 

Mar. 

Feb. 

Oct. 

April 

Feb. 

Mar. 

April 

Aug. 

July 

Jan. 

July 

Mar. 

Oct. 

Feb. 

July 

Dec. 

May 

May 

Sept. 

Mar. 

July 

May 

April 

Mar. 

Mar. 

Jan. 

Jan. 

Jan. 

Sept. 

Jan. 

June 

Jan. 

Oct. 



6, 1896 
30, 1897 

7, 1896 

20, 1897 
17, 1892 

26, 1882 

1, 1896 

IS, 1879 

17, 1897 
17, 1878 

22, 1895 

23, 1880 

15, 1887 

8, 1876 

17, 1883 

18, 1886 

11, 1876 
23, 1879 
23, 1895 
22,, 1895 
2Z, 1895 

3, 1892 

22, 1879 

2, 1886 

9, 1897 

28, 1879 
14, 1896 

7, 1893 

21, 1882 

4, 1882 
I, 1882 

16, 1872 
14, 1808 

23, 1872 

3, 1868 

17, 1871 
16, 1869 

1, 1873 

27, 1870 

30, 1865 

29, 1866 

2, 1873 

12, 181 1 

31, 1877 

28, 1872 
16, 1895 

30, 1897 

13, 1866 
12, 1886 
12, 1886 
12, 1886 

4, 1888 

22, 1884 

11, 1889 
A, 1887 

12, 1897 



USE. 



1 165 



APPLIANCE. 



NAME OF INVENTOR. 



)ATE OF ISSUE. 



NO. 



Bausman 

Bailsman 

Beaumont 

Benster 

Bercher 

Bergman 

Berry 

D. Bickford 

Bole 

Bolton 

Boynton 

Bramwell 

Brock 

R. Cameron 

Chapman 

P. Chick 

Clark 

Close 

Coffield 

Colman 

Colman 

Connolly 

Cook 

Cook 

Coon 

Corey 

Cramer 

Davey 

Denney 

Depp 

W. Deukmann 

Durand 

Eastman 

Eckart 

Eimecke 

P. A. Ensign 

Ericsson 

Ericsson 

J. Ericsson 

J. Ericsson 

J. Ericsson 

J. Ericsson 

J. Ericsson 

Eteve & DeBraan. . 

Field 

Fletcher&Huggings 

Genty 

Gibbs 

Goth 

Good 

Good & Marichal. . 

Graham 

Griswold 

Hall 

Hall 

Hanover 



May 

Mar. 

Sept. 

Nov. 

April 

Nov. 

May 

June 

Oct. 

Mar. 

Dec. 

July 

Aug. 

Nov. 

Feb. 

Dec. 

July 

July 

July 

May 

May 

June 

Jan. 

Feb. 

Mar. 

Jan. 

Mar. 

Jan. 

April 

June 

Dec. 

May 

Dec. 

June 

Jan. 

Oct. 

Mar. 

July 

Nov. 

July 

April 

Dec. 

Oct. 

Dec. 

Oct. 

Oct. 

July 

Oct. 

April 

May 

April 

July 

June 

Aug. 

Aug. 

Jan. 



27, 1884 
10, 1885 
21, 1880 
10, 1891 
21,1896 

10, 1891 

11, 1897 
6,1865 

26, 1897 
24, 1885 

1 1, 1883 

30, 1895 
19, 1890 

12, 1867 
24, 1891 
18,1866 
24, 1888 
12, 1887 

21, 1885 
5,1885 

12, 1885 

22, 1875 

2:i, 1883 
20, 1883 

10. 1896 
20, 1885 

4, 1884 

9, 1877 

22,, 1895 

19, 1894 

16, 1862 

9,1893 
30, 1890 

17. 1879 
2,1883 
2,1866 

30. 1880 

8, 1890 
4, 185 1 

31, 1855 
15, 1856 
14, 1858 

9, i860 

30, 1884 
10, 1893 

8, 1895 

31. 1888 
26, 1897 

13. 1897 
26, 1896 

28. 1896 
22, 1884 
30, 1891 

4. 1891 
4, 1891 
6,1885 



299,325 
313,646 
232,438 
463,092 
558,475 
463,025 
582,257 

48.043 
592,688 
314,218 
289,967 
543,462 
434,422 

70,800 
447,066 

60,474 
386,454 
366,204 
322,796 
317,093 
317,628 
164,809 
271,040 
272,656 

555,929 
311,106 
294,369 
186,119 
538,068 
521,762 
37,155 
497,048 
443.641 
216,563 
270,036 

58,397 
226,052 

431,729 

8,481 

13,348 

14,690 

22,287 

30,306 

309,835 

506.486 

547.718 

387,063 

592,246 

580.600 

560.707 

558.944 
302,246 
455.201 
457.272 
457,273 
310,419 



n66 



USE. 



APPLIANCE. 



NAME OF INVENTOR. 



DATE OF ISSUE. 



Air Engine 



Hanser & Whittaker 
Hardie & James. . . 

Harder 

Hill 

O. M. Hillman.... 
O. M. Hillman.... 

Hock & Martin 

Humes 

Hurd 

Jefferson 

E. Langen 

F. J. Laubereau .... 

Leavitt 

Leavitt 

J. J. Lenoir. 

Limpus 

Lochmann 

R. Lord 

Lyman 

A. S. Lyman 

Martin 

Matthes 

Maxim 

McCalla 

McDonough 

T. McDonough.... 

McKinley 

McKinley 

McKinley 

J. McLeish 

McTighe 

McTighe 

McTighe 

McTighe 

H. Messer. 

Metzing 

Middleton 

Mihsb'ch&Groeschel 

Musselman 

D. Myers 

R. Napier 

Nash 

H. Norman 

H. M. Paine 

Parke 

Parsons 

R. Peters 

Philpott 

Pollock 

Presbrey 

Reynolds 

B. F. Rice 

Rider 

Rider 

Rider 

Rider 



Jan. 

June 

Oct. 

July 

June 

June 

May 

April 

Sept. 

Dec. 

Aug. 

April 

Oct. 

July 

Mar. 

Nov. 

Jan. 

Sept. 

Jan. 

Feb. 

June 

April 

Feb. 

Feb. 

May 

Sept. 

July 

Jan. 

Jan. 

Dec. 

July 

June 

June 

June 

Jan. 

Nov. 

Sept. 

Sept. 

Aug. 

Nov. 

Sept. 

May 

Feb. 

J^ov. 

Dec. 

Nov. 

Nov. 

Mar. 

April 

Aug. 

Aug. 

April 

[an. 

Sept. 

fuly 

Oct. 



3, 1893 
17, 1879 
14,1890 

13, 1880 
26, i860 
26, i860 

8, 1877 
2, 1889 

8. 1885 
1, 1891 

13, 1867 

ID, 1849 
28, 1884 

14, 188s 
19, 1861 

10, 1885 

5. 1886 
17, 1861 
25, 1881 

28, 1854 
2.7, 1893 

8, 1879 

5, 1884 
4, 1890 

29, 1883 
23, 1856 
30, 1878 
18, 1887 
18, 1887 
10, 1872 

7, 1885 
3, 1890 
3, 1890 
3, 1890 

6, 1863 

18, 1890 
22, 1874 

I, 1896 

8, 1893 

IS, 1870 

19, 1854 
22, 1883 
25, 1873 

30, 1858 

7, 1897 
12, 1895 
18, 1862 
IS, 1887 
28, i88s 
24, 1880 

I, 1882 
S, i8S9 



187s 
1875 
1878 

1879 



489,148 
216,611 
438,251 
229,82; 
28,910 
28,911 
190,490 
400,850 
325,805 
464,364 

67,659 

6,301 

307,312 

321,985 

31,722 

329,914 
333,644 

33,308 
236,954 

io,57t) 
500,340 
214,050 
293,185 
420,824 
278,446 

15,771 
206,597 
356,146 
356,147 
133.713 
321,739 
429,281 
429,282 
429,283 

37,299 
441,103 
155,328 
566,785 
502,860 
109,338 

11,696 
278,257 
136,259 

22,219 
594,901 
549,741 

36,964 
359,282 
316,656 
231,446 
262,119 

23,495 
158,525 
167,568 
206,356 
p20,309 



USE. 



167 



APPLIANCE. 



NAME OF INVENTOR. 



DATE OF ISSUE. 



NO. 



Rider 

Rider 

Rider 

Rider 

A. K. Rider 

A. K. Rider 

Riley • 

Robinson 

Robinson 

Roediger 

Rogers 

Rogers 

Rusk 

Schmid & Beckfeld 

Schmid & Beckfeld 

Schnake . 

Schou 

Serdinko 

P. Shaw 

Sherman 

Sherrill 

Shilling 

Smith 

Stevens 

Stevens 

Stewart 

Tasker 

Thuemmler 

Thuemmler 

Vivian 

Walling 

Ward 

Weimer 

Wilcox 

Wilcox 

Wilcox 
Wilcox 
Wilcox 
A. O. Wilcox.. 

S. Wilcox 

S. Wilcox 

S. Wilcox 

S. Wilcox 

Winchell 

Wood 

Woodbury et al . 
Woodbury et al. 
Woodbury et al . 
Woodbury et al. 
Woodbury et al. 
Woodbury et al. 
Woodbury et al. 
Woodbury et al. 
Woodbury et al. 
Woodbury et al. 
Woodbury et al. 



(re-issue) . 
(re-issue) . 



July 

Nov. 

Nov. 

Nov. 

Jan. 

Oct. 

June 

Dec. 

Feb. 

Mar. 

May 

Jan. 

Aug. 

May 

Feb. 

Nov. 

Nov. 

Feb. 

May 

Mar. 

April 

June 

Feb. 

Sept. 

Oct. 

May 

June 

Sept. 

Oct. 

Sept. 

Aug. 

Jan. 

Feb. 

Dec. 

Dec. 

June 

Oct. 

Dec. 

July 

May 

Nov. 

Nov. 

Sept. 

April 

Aug. 

June 

June 

June 

June 

June 

June 

Aug. 

A.ug. 

A.ug. 

Sept. 

Oct. 



13, 1886 
23, 1886 
27, 1688 

27, 1888 
17, 1871 
24, 1871 

29, 1875 
9, 1884 

3, 1891 

30, 1897 

13, 1890 
2, 1894 

18, 1891 

14, 1889 
18, 1890 

28, 1876 
21, 1893 

2, 1886 

2, 1854 
12, 1895 

I, 1879 
16, 1885 

14, 1893 

16, 1884 

29, 1889 

15, 1894 
7, 1887 

28, 1880 
12, 1880 
30, 1890 

4, 1896 

T, 1878 
23, 1897 

4, 1883 
4, 1883 

3, 1884 

7, 1884 
15, 1885 

19, 1853 
3, 1859 

20, i860 
20, i860 
19, 1865 

17, 1888 

18, 1885 

8, 1880 
8, 1880 
8, 1880 
8,1880 
8, 1880 
8, 1880 

11,1885 

II, 1885 

II, 1885 

1,1885 

6, 188s 



345,450 
353,004 
393,663 
Z9Z,7^2 
111,088 
120,325 
165,027 
309,163 

i 445,904 
579,654 
427,911 
511,969 
458,070 
403,294 
421,525 
184,913 
508,990 

335,388 

10,868 
535.602 

213,783 
320,182 

491,859 

305,114 

414,173 

519,977 

1364,451 

1232,660 

|233,i25 

437,320 

'565,191 

1 198,827 

1 577.568 

1289,481 

j 289,482 

10,486 

10,529 

332,312 

9,871 

23,876 

30,700 

30,701 

50,061 

381,313 

324,510 

228,712 

228,713 

228,714 

228,715 

228,716 

228,717 

324,0(^0 

324,061 

324.062 

325.640 

327.748 



ii68 



USE. 



/PPLIA -^. 



Air Engine 

(( 

€t 

tt 

Air and Gas Engine 

(C It 

Air and Liquid Cooler 

Air and Steam Engine 

Air-Heating 

Air and Steam Jet Combustion. . . . 

Air-Supply and Boilers 

Apparatus for Cooling Air 

« (( « 

Apparatus for Navigating the Air. 
« « (( 

" Purifying " 

" Removing Dust from 

the Air 

" Supplying Continuous 

Flow of Air 

" Transmitting Air Power 

tt (I (C 

Compressed Air Bath 

Cylinder 

" Engine 

« « 

(( <( 

<( (( 

Heater.'.'.'.!'.'.!*.'.*. 

Spring 

Fresh Air Apparatus 

Hydraulic Air Compressor 

(( « 

« (( 

(I It 

tt ft 

Method of Heating Air 

tt tt tt 

Process for Mixing Air and Steam 



NAME OF INVENTOR. 



DATE OF ISSUE. 



Woodbury et al . . . . 

Woodbury et al 

Woodbury et al . . . . ' 
J. A. Woodbury. . . 
J. A. Woodbury. .. 

Wright 

A. H. De Villeneuve 

D. Dick 

J. F. Haskins 

O. Trossin 

P. Shearer 

D. E, Somes 

F. B. Blanchard... 
O. M. Hillman.... 
L. C. St. John 

G. M. Copeland. . . . 

G. E. Hibbard 

T. D. Kingan 

D. E. Somes 

C. McDermott 

W. F. Quinby 

A. S. Lyman 



J. D. Whelpley... 

B. Rouquarol 

H. Calf 

H. Calf 

P. T. Ware 

G. M Goodwin . . . 

D. Bickford 

A. Parsey 

A. M. Smith 

W. M. Storm 

W. C. Turnbull... 

H. Bushnell 

L. Bissel 

J. McNeven 

M. Hey 

M. Hey 

W. D. Leaf 

C. Moore 

W. E. Prall 

A. C. Fletcher..., 
J. Hollingsworth. 
O. M. Storm 



Dec. 

Dec. 

May 

May 

Oct. 

Aug. 

Mar. 

April 

July 

July 

Sept. 

Mar. 

July 

Aug. 

Oct. 

Feb. 

Dec. 

Dec. 

Nov. 

Nov. 

Nov. 

Jan. 



1,1885 
I, 1885 

28, 1889 
17, 1853 

4, 1853 
13, 1889 
19, 1872 

9, 1867 
16, 1872 
22, 1873 

3, 1861 

29, 1870 
10, 1855 

9, 1864 
7, 185 1 
26, 1867 
16, 1873 
16, 1873 
12, 1867 
12, 1872 
26, 1861 
19, 1864 



July 
Aug. 
Sept. 



Mar. 6, 1866 

Mar. 20, 1866 

Aug. 24, 1869 

Jan. 18, 1870 

May 8, 1866 
March i, 1870 

May 15, i860 
31, 1847 
8, 1871 

^^t-.. 23, 1851 

April 17, i860 

July I, 1873 

Oct. II, 1841 

Sept. 14, 1869 

April 26, 1870 

July 25, 1 87 1 

June 14, 1870 

July I, 1873 

Nov. 7, 1871 

May 19, 1863 

June 5, i860 

April 5, 1853 



^^' 



CONTENTS. 



PAGES. 

Production 1-254 

Transmission 255-330 

Use 331-1152 

Patents T153-1168 



INDEX. 



f PAGE 

ABSTRACT of Thesis Test of 
Compressed Air Power 

Plant at Jerome Park, N. Y. 193 
Account of the Attempts to In- 
. troduce Compressed Air for 

Steering Vessels 1106 

Advantages of Compressed Air 

for Transmitting Power 257 

Air Beds 1082 

Air in Bottles 322 

Air Brake 412 

Air Brake Service 413 

Air Cars 422, 424* 425» 430 

Air Cars in New York City.... 491 

Air Compressors 134 

Air Compressor Cylinder 143 

Air Compressor Explosions 156 

Air Compressor Hartford 170 

Air Compressors at High Alti- 
tudes 123 

Air Discharges from Pipes Under 

Heavy Losses of Pressure.... 269 
Air vs. Electricity in Long Dis- 
tance Transmission 260 

Air Gun 902 

Air Heating, Electric 410 

Air Hoists 548 

Air Hoists in Mining Operations 551 
Air Hoists, Self Propelling, with 

Unlimited Travel 560 

Air Jet Pumps 655 

Air Lift, Telescopic 559 

Air as a Lubricant 1106 

Air Meters 1068 

Air Motor Car, Hardie 490 

Air Motors for Copenhagen.... 1068 

Air Motor 385-490 



PAGE 

Air Motor Operating Pillar and 

Gantry Cranes 591 

Air Pipes 276 

Air Power S 

Air Power and Auto Truck Com- 
panies 497 

Air Power Cars in Chicago 432 

Air Power Reflections 433 

Air Pressure Pump with Adjust- 
ing Receiver 615 

Air Pumps 185 

Air Pumping .598-600 

Air for Ship Building 804 

Air Surface Condenser iioi 

Air Used in Engines 384 

Air Wagons 112 

Air on War Ships 1 126 

Allen Refrigerating Process 1000 

Alphabetical List of Inventions, 

1153-1168 

American Air Power Co 500 

An Account of the Attempts to 
Introduce Compressed Air for 

Steering Vessels 1 106 

An Air Wagon 501 

An Explosion in the Receiver of 

an Air Compressor 149 

An Air Hoist for Mercantile 

P^-. 552 

An Indepenuo t Motor to Utilize 

Brake Energy 419 

An Inertia Valve Percussive 

Tool 908 

Annual Mf^ing of the American 

Air Power Co 500 

An Old Underground Pneumatic 

Tube 890 



iiyo 



INDEX. 



PAGE 

Application of Compressed Air 

to Cranes and Hoists 588 

Appraisers' Stores Building — 

Painted by Air 852 

Application of Compressed Air in 

Railroad Shop Practice 815 

Artificial Ice 994 

Automatic Air Brake 413 

Automatic Air Pump 185 

Automatic Brake, Quick Action. 415 
Automobile Compressed Air Fire 

Engine 503 

Automatic or Direct Air Brakes 

for Street Railways 416 

Automobiles and Traction 463 

pALLAST Injector 1045 

^ Beaumont, Col. R JE 1128 

Belt-Driven Air Compressors for 

Shop Service 183 

Belly Pounder 1050 

Blasting Agents 768 

Bottles Filled with Air 322 

Bolt Cutting Machine 899 

Boiler Shop Equipments 794 

Bottle Test 322 

Brief History of Liquid Air.... 711 

Broadway Tunnel 537 

Brunei 1 129 

^ARVING and Dressing Stone. 1114 

^^ Cars Dumped by Air 1109 

Caskey Portable Hydro-Pneu- 
matic Riveter 924 

Central Power Plants 203 

Central Power Schemes 206 

Chicago Air Power Cars 432 

Chimes 1077 

Cinder Hoist on the D. S. S. & 

A. R. R 557 

Cleaning Car Cushions by Com- 
pressed Air 1 108 

Cleaning of Carpets 1059 

Cleaning Structural Iron bv Sand 

Blast 1012 

Clock by Air 1083 

Col. Prout on Pneumatic Trac- 
tion 443 

Collection of Blacksmiths' Tools. 948 
Cold Storage and Cold Rooms, 

from Compressed Air 1001-1005 

Combustion in Liquid Air 774 

Compound Direct Air Pressure 

Pump with Adjusting Receiver. 615 
Compressed Air Applied to Trav- 
eling Motors by a New Method. 544 



PAGE 

Compressed Air 81 

Compound Air Compressor Cyl- 
inder 143 

Compressed Air Central Plants. 188 
Compressed Air and Its Distri- 
bution for Power Purposes in 
the City of Paris — How it Is 
Produced, Its Numerous Appli- 
cations and Its Cost 213 

Compressed Air Dredger for 

Gold Mining 829 

Compressed Air Drilling Ma- 
chine 898 

Compressed Air Dry Docks.... 1104 
Compressed Air Economies in the 

Foundry 702 

Compressed Air Efficiencies 381 

Compressed Air vs. Electricity.. 96 
Compressed Air and Electricity 

at Pori Chalmette 544 

Compressed yAir in England 78 

Compressed Air in Europe 395 

Compressed Air Fire Engine... 503 
Compressed Air in the Foundry. 695 
Compressed Air Flow in Pipes. . 292 
Compressed Air Handling Water 

Ballast in Ships 691 

Compressed Air Haulage Plant at 
No. 6 Colliery of the Susque- 
hanna Coal Co., Glen Lyon, Pa. 519 
Compressed Air on the Holland 

Torpedo Boat 1069 

Compressed Air Locomotive on 
the New York Elevated Rail- 
road 518 

Compressed Air Locomotives... 516 
Compressed Air and Liquid Air 
as Used in the Simplon Tunnel 

Construction y'j}, 

Compressed Air in Machine 

Shops and Foundries 784 

Compressed Air Metering 382 

Compressed Air in Mines 824 

Compressed Air Motors 455 

Compressed Air Plant at Ains- 

worth 242 

Compressed Air Plants, Relative 
Efficiencies Above and Below 

Sea Level 104 

Compressed Air Power Plant at 

Jerome Park, N. Y 843 

Compressed Air as Used for 

Power Purposes 355 

Compressed Air, Its Production, 

Transmission and Use 67 

Compressed Air Production t^ 

Compressed Air Progress 34c 



INDEX. 



1171 



PAGl 

Compressed Air Refrigeration — 

The Earliest Ice Machine 993 

Compressed Air Reheating 398 

Compressed Air Reheated with 

Steam 404 

Compressed Air Riveting Plant. 945 
Compressed Air in a Rolling 

Mill 797 

Compressed Air in a Salt Well. 663 

Compressors — Specification of . . 123 

Compressed Air in a Saw Mill.. 812 

Compressed Air in Shops 803 

Compressed Air Street Cars. .450, 452 
Compressed Air Street Railway 

Operation 482 

Compressed Air Substituted for 

Steam 350 

Compressed Air for Supplying 

Water 654 

Compressed Air Tramway 477 

Compressed Air Transmission 

Plant at the North Star Mine. 288 
Compressed Air for Transmis- 
sion of Power 283 

Compressed Air Truck 498 

Compressed Air Tunneling 823 

Compressed Air versus Trolley. 190 

Compressor Used in Bridge 178 

Work 178 

Compressed Air Used for Hand- 
ling Baggage 555 

Compressed Air in Underground 

Work 826 

Convenient Devices in a Railroad. . 

\ Yard 592 

Conti-System 478 

Cost of Operating Air Cars in 

New York 491 

(Cost of Production of Com- 
pressed Air in Paris 238 

pranes and Hoists 588 

Curves Showing Temperature of 

.Air During Compression 113 

Cyanide Process 819 

I^EATH Among Caisson 

^ Workers 1 126 

Death of Thomas Doane 1129 

Development of Pneumatic Dis- 

( patch Tubes 871 

Diminutive Air Compressor 165 

pischarge of Air from Pipes Un- 
der Heavy Losses of Pressure. 269 

Displacement Pumps 669 

'Oixon, Tils., Water Works 658 

,Dont's for Users of Compressed 

. Air 347 

Orilling and Riveting on the Ele- 

^ vated Railroad, N. Y 932 



PAGE 

Driving Drift PiTis with a New 

Device 947 

Driving Pumps by Compressed 

Air 671 

Drop Pit Jack 904 

Dudley's Air Gun 1086 

Dutton Pneumatic Balance for 

Canals 567 

p ARLY Pneumatics 6 

^" Economy of Compressed Air 

Power Transmission 289 

Economies Effected by Com- 
pressed Air 346 

Economies in the Use of Com- 
pressed Air 374 

Efficiency of Compressed Air En- 
gines 381 

Electric Air Hl ting 410 

Electricity and Compressed Air. 96 

Electrically Compressed Air 992 

Electric Cotton Hauler at Port 

Chalmette, La 526 

Electricity in Mining 830 

Electricity at Port Chalmette 528 

Electrolysis 1131 

Elevated Railroad Shops 787 

England, Compressed Air in 78 

Equipment for Boiler Shops 794 

Explosions, Air Compressor 156 

Explosions in Air 153 

Experience with Compressed Air 
in Shipbuilding and Shipyard 

Work 1115 

Explosions and Ignitions^ in Air 

Compressors and Receivers... 150 

Experimental Mechanics 105 

Experiments on the Reheating of 

Compressed Air 410 

Explosions in Receiver of an Air 

Compressor 149 

Explosions 154 

TACTS in Regard to Air Power 

' and Auto Truck Companies. 497 

Fire Alarm Whistle 1087, 1088 

Fire Engine 503 

Firing 145 

First Street Railway 479 

Flow of Compressed Air in Pipes 292 

Foster Regulator 1058 

Foundry Air Compressor 190 

Foundries, Compressed Air in... 784 

Foundry 695 

Foundry Plant 705 

For Shop Use: Pump vs. Com- 
pressors 693 

Freezing in Compressed Air 324 

Freezing 325, 326 



'\ 



tl?2 



INDEX. 



PAGE 

Furnace Door Hoist^ at Parkgate 565 
Freezing of Ground by Expan- 
sion of Air 1009 

GASOLINE Air Compressor 

for Bridge Work 178 

Gleason- Peters Pump 187 

Golden Wave Mine Power Plant 

at Congress, Ariz 833 

Granite Surfacing Machine 11 13 

Growing Interests in Compressed 

Air 66 

LI ANDLING Baggage by Com- 

■■ pressed Air 555 

Handling Switches and Signals. 968 
Handling Water Ballast in Ships 

by Compressed Air 691 

Handler, at Port Chalmette, La.. 526 

Hand vs. Air Riveting Power... 926 

Hardie Air Motor Car 489 

Hartford Air Compressor. .' 170 

Hardie Air Motor Car 489-490 

Hardie Cars Running in Chicago. 485 

Hardie New Valve Gear 486 

Haulage 533 

Haulage Plant 519 

History 331 

History of Liquid Air 711 

Hoadley-Knight System 456 

Hoists and Cranes 588 

Hoists 548-554 

Hoists, Self-Propelling, with Un- 
limited Travel 560 

Hopscraft's Pneumatic Railway. 535 

Houston Pneumatic Track Sander 1057 

Hughes & Lancaster Car 479 

Hydraulic Air Compression 1121 

Hydraulic Compression of Air. . 171 
Hydraulic Plant for Compressing 

Air 173 

I GNITIONS and Explosions in 
■ Air Compressors and Re- 
ceivers 150 

Improved Pneumatic Displace- 
ment Pumps 665 

Improved Pneumatic Tools for 

Foundry Use 892 

Improved Quarry Plant 832 

Inlet and Outlet Valve Areas in 
Comparison to Those of Air 

Cylinders 112 

In and About Railroad Machine 

Shops 786 

In the Shops 792 

Intercoolers 137 

Is Compressed Air Destined to 
Become the Rival of Elec- 
tricity ? 248 



pagK| 

JARVIS Pneumatic Car 476 \, 

^ Jerome Park Power Plant.. 843 ' 

Jets of Air 854 

Jet Pumps 655 

tr ING-RIEDLER Air Com- 
■ ^ pressor Tested at the Rose 

Deep Mine, S. A 199 

Krause Air Filter 1066 



I ATENT Heat of Evaporation 

^ of Liquid Air 7271 

Letters 58, 65, 118, 121, 139, 160 

Lifting Water by Compressed 

Air 646 

Liquid Air for Automobiles 766 

Liquefaction of Air 725 

Liquid Air 711, 713, 724 

Liquid Air as a Blasting Agent.. 768 

Liquid Air as a Cure 768 

Liquefaction of Air by Dynamical 

Action 736 

Liquid Air as an Explosive 770 

Liquid Air in Gas Making 772 

Liquefying Hydrogen 767 

Liquid Air and Low Tempera- 
ture 751 

Liquid Air as a Means for the 

Manufacture of Oxygen 743 

Liquid Air in Medicine and Sur- 
gery 772 

Liquid Air as a New Source of 
Power. Another Engineering 

Fallacy 756 

Liquid Air Possibilities 759 

Liquid Air and Its Uses 746 

Lifting Water by Compressed 

Air 646 

Locomotive Bell Ringer 901 

Locks for Canals 567 

Locomotives 516 

Locomotive Fire Kindler 11 10 

London's Lost Tunnel 538 

Loss of Loads in Air Pipes 276 

Low Pressure Pneumatic Inter- 
locking at Jersey City. . ._ 986 

Lyman Pneumatic Interlocking at 

Jersey City 9^6 

ll/l ACHINE for Fitting Vehicle 

■''■ Spring 1095 

Machine Shop, Compressed Air. 784 
Mail Tubes in Times of a Bliz- 
zard 870 

Mail Tube System 867 

Manhattan Elevated Railroad I 

Shops 787 f'l 

Mannesmann Steel Bottle Test.. 322 



INDEX. 



1173 



PAGE 

Vlason Painting Machine 858 

Vleeting of the American Air 

Power Co 500 

VIechanical Application of Com- 
pressed Air 783 

VIechanical House Cleaning 1063 

viedicine and Surgery 772 

VIegaphones in Fog Signalling. . 1098 

Vlekarski Car at Toledo, Ohio. . 455 
Vlekarski System at Berne, 

Switzerland 453 

^len Prominent in Compressed 

Air Developments 332 

vietering — Compressed Air 382 

vlicrobes Thrive on Liquid Air. 771 

vline Haulage 533 

vline Hoists : 554 

alining Operations 551 

^odel Compressed Air Foundry 

Plant 705 

^onon Railroad Shop 805 

klotors, Compressed Air 455 

Municipal Power Plant 309 

VIEW Air Power Car, Trial 

^ of 448 

Tew Bolt Thread Cutter 1087 

'Jew Canal Locks 1 105 

sfew Device for Reheating Com- 
pressed Air for Use in Pumps. 400 

Jew Gas Generator 530 

Jew Method for Applying Com- 
pressed Air to Traveling Mo- 
tors 544 

Jew Portable Pneumatic Ram- 
mer 942 

Jew York Railroad Commission 

Tests of Street Car Brakes. .. . 417 

lorwich Sewerage Works 684 

lorth Star Mine 288 

lotes 1132-1152 

Jew Tramway 432 



3RDES Liquid Fuel Burner... 1097 
, Oxygen Manufactured by 

Means of Liquid Air 743 

3AINTING by Air Appraisers' 

Stores Building 852 

ainting Buildings by Com- 
pressed Air 855 

ainting by Compressed Air.... 846 

ainting Machine . , 858 

aint for Pneumatic Spraying.. 850 
illar and Gantry Cranes Opera- 

ated by Air Motors 591 

lant for the Commercial Manu- 
facture of Liquid Air 775 

lants 188 



PAGE 

Pneumatic Balance Locks for 

Canals 567 

Pneumatic Belt Shifter......... 1091 

Pneumatic Caisson Foundations 
for the Broad Exchange Build- 

N. Y. City 1025 

Pneumatic Caisson for Ordinary 

Foundations 1017 

Pneumatic Car 476 

Pneumatic Carpet Renovator 1061 

Pneumatic Cesspool Excavator.. 690 

Pneumatic Check System 1075 

Pneumatic Cyanide Process 819 

Pneumatic Dispatches ...860, 863 

Pneumatic Displacement Pumps, 

665, 669 
Pneumatic Dispatch Tube System 
in the Illinois Trust and Sav- 
ings Bank Bldg., Chicago 885 

Pneumatic Dispatch Tubes 866 

Pneumatic Elevator L>oor Mech- 
anism 1052 

Pneumatic Elevator Safety 1091 

Pneumatic Equipments for Boiler 

Shops 794 

Pneumatic Furnace Door Hoists 

at Parkgate 565 

Pneumatic Gun in Warfare 1053 

Pneumatic Sand Rammer 905 

Pneumatic Horse Collars 1090 

Pneumatic Interlocking 972 

Pneumatic Letter Copy Book.... 1090 

Pneumatic Mail Tube System 867 

Pneumatic Painting Machines... 856 

Pneumatic Planer Feed 1073 

Pneumatic Propulsion 444 

Pneumatic Railway 535 

Pneumatic Tools 895 

Pneumatic Traction 437, 439 

Pneumatic Traction in New York 438 
Pneumatic Traction (Col. Prout, 

^ on) 443 

Pneumatic Tubes 863 

Pneumatic Work 1039 

Port Chalmette 528 

Popp Compressed Air Motors for 

Tramway Traction 509 

Popp System 471 

Popp Conti System 478 

Portable Air Compressing Outfit. 95 

Portable Motor 1055 

Portable Pneumatic Riveters in 

Ship Building 936 

Possibilities of Liquid Air 759 

Power Plant of Golden Wave 

Mine, Congress, Ariz 833 

Power Plant at Jerome Park, 
N. Y 843 



1174 



INDEX. 



PAGE 

Practical Applicatidti of High 
Range Compressed Air Power 

Transmission 316 

Practical Painting by Air. .^ 850 

Progress in Compressed Air 349 

Proposed Extension of the Use of 
Compressed Air on Men-of- 

War 392 

Proposed Underground Railroad 

on New York 525 

Pumping by Air 598 

Pumping by Compressed Air. 600, 604 
Pumps vs. Compressors for Shop 

Use 693 

Pumping Water by Air 653 

QUARRY Plants 832 

^^ Quick Action Automatic 

Brake 415 

DATIOS of Areas of Inlet and 
■■ Outlet Valves to that of the 

Air Cylinders 112 

Railroad Machine Shop, in and 

about 786 

Railroad Shop (Monon) 805 

Railroad Devices 592 

Railways 479 

Recent Experiments in Com- 
pressed Air Motors 181 

Recent Experiments in Tamping 

Track by Compressed Air 1046 

Recent Progress in the Develop- 
ment of Pneumatic Dispatch 

Tubes 871 

Reducing Air from High to Low 

Pressure 127 

Reflections — Air Power 433 

Refrigeration by Compressed Air 995 
Regulating Temperature of Build- 
ings by Compressed Air 1036 

Reheating Compressed Air 398 

Reheating Compressed Air with 

Steam 404 

Reheating Compressed Air for 

Uses in Pumps 400 

Relative Efficiencies of a Com- 
pressed Air Plant Due to Dif- 
ference of Level Above and Be- 
low Sea Level 104 

Remarkable Chip 1 125 

Report on the New Hardie Air 
Motor Cars now in Use on the 
28th and 29th St. Line, N. Y. . 474 
Report on Trials Made at Magog, 
Quebec, to Test the Economy 
Effected by Reheating Com- 
pressed Air 2ip 



PAGl 



Right Way and Wrong Way to 
Place Compressed Air in Com- 
petition with Electric Railways 506 

Rock Cutting Apparatus for Min- / 

ing and Quarrying -, . , . 822' 

Rock Drills Worked by Electri- 
cally Compressed Air 821 

Rolling Mill, Compressed Air in a 797 

Ruth Pneumatic Car Furnishings 1089 

SAFETY in Air 387 
Sand Blast Process as Ap- 
plied to the Cleaning of the 
Walls of Pardee Hall, La- 
fayette College 1014 

Sand Blast 1013 

Sand Blast Method loii 

Sargent Gas Engine Oiler 1099 

Sawmill, Compressed Air in a... 812 

Schemes 206 

Self Propelling Hoists, with Un- 
limited Travel 560 

Separation of the Constituent 
Gases of Liquid Air, Distillation 
of the Gases — Work of Com- 
pressors, Cost of Power 731 

Service — Air Brake 413 

Sewerage Works 684 

Sheep Shearing in Australia 1103 

Ship Building 804 

Shops, Compressed Air in 803 

Sinking Cylinder Foundations in 

Valparaiso. 1032 

Simplon Tunnel Construction ... . 'j'j^i 
Skin Diseases Cured by Liquid 

Air 768 

Some of the C6nvenient Devices 

in a Railroad Yard 592 

Some Figures on the Cost of 
Pumping with the Pohle Air 

Lift 659! 

Something New in Jail Construc- 
tion 1083 

Some of the Uses and Advantages 

of Compressed Air 341 

Speed in Air Compressors 140 

Spreader Car — G. C. & S. F. Ry.. 1038 
Special Stop Cock for Compressed 

Air Pipes 321 

Sterilized Air for the Preserva- 
tion of Fruits and Provisions.. 1081 
Street Railway, Automatic or 

Direct Air Brake for 416 

Stone Cutting by Air Tools 11 12 

Street Railway Operation 482 

Storage of Air in Bottles 322 

St. Gothard Tunnel Ventilation. . 
Street Car§ ................. .4^0, 45? 



I 



iNDE^. 



1175 



PAGE 

Supply of Water by Compressed 
Air 654 

Surfacing Railroad Track by 
Means of Compressed Air 1043 

Susquehanna Coal Co. at Glen 
Lyon, Pa., Compressed Air 
Haulage Plant 519 

TAYLOR Hydraulic Air Com- 

' pressor 166 

Telescopic Air Lif^ 559 

Temperature of Air Shown by 

Curves During Compression... 113 
Tests of a Four-Stage Air Com- 
pressor 190 

Tests of a King-Riedler Air Com- 
pressor at the Rose Deep Mine, 

S. A 199 

Tests of Street Car Brakes by the 

New York R. R, Commission. . 417 
Thesis Test of a Compressed Air 
Power Plant at Jerome Park, 

N. Y 193 

Thomas Pneumatic System of 
Handling Railway Switches and 

Signals 954 

Tilden Pneumatic Hammer 1127 

Tools for Stone Working iiii 

Traction and Auto-Mobile 463 

[Traction — Pneumatic 437, 439 

Trial of a New Power Car 448 

Tramway Traction 509 

Tramway 432 

transmission, Uses and Advant- 

( ages of a Public Supply of C. A. 255 

Transmitting Power, Advantages 

^ of Compressed Ai^^ for 257 

Transmission Through Pneumatic 

Tubes 891 

Transmission of Po)jver by Com- 

' pressed Air 283 

Transmission Plant a( the North 

^ Star Mine 288 

Transmission, Use arid Produc- 
tion of Compressed Air dy 

Trucks, Compressed Air 498 

Tunneling by Compressed Air... 823 



UNDERGROUND Railway in 



New York 



525 



PAGE 

Underground Work 826 

Uses and Advantages of Com- 
pressed Air 341 

Use of Compressed Air at a Blast 
Furnace Plant 708 

Use of Compressed Air in Build- 
ing the Delaware Breakwater.. 835 

Use of Compressed Air in the 
Freight Yard of the Lake Shore 
& Michigan Southern Ry. at 
West Seneca, N. Y 979 

Use of Compressed Air in Found- 
ries 99 

Uses of Liquid Air 746 

Use of Compressed Air in Mines. 824 

Use of the Pneumatic Chipping 
Tool in Chipping Refactory Ma- 
terial for Furnace Work 900 

Use of Compressed Air in a Salt 
Mill (^Z 

Usefulness of Compressed Air 
Under Difficulties 387 

Use of Water Powers by Direct 
Compression Ratios 107 

VENTILATION of the St. 
Gothard Tunnel 828 

Views of a Non-Expert 10 

Vincennes - Villi - Evrard Com- 
pressed Air Tramway 477 

Volumes of Air in Engines 384 

Volumetric Efficiency of Air Com- 
pressors at High Altitudes 98 

Volumetric Efficiency in Air Com- 
pressor Practice 103 

WAGONS SOI 
War Ship Run by Com- 
pressed Air 389 

Water and Air 594 

Water Lifted by Compressed Air. 646 

Water Works at Dixon, Ills 658 

Weight of Air 129 

Weight of an Air Compressor. . . 134 
Working Rock Drills by Electri- 
cally Compressed Air 821 

yEAKLEY Vacuum Power 
■ Hammer 907 



II76 



ADVERTISEMENTS. 



AIR AND GAS 
COMPRESSORS 

OF THE HIGHEST EFFICIENCY. 

ALL TYPES AND SIZES 
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OUR 'IMPERIAL" COMPRESSORS 
ARE PARTICULARLY ATTRACTIVE. 




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ROCK DRILLS 

THAT DO THE WORK. 
OUR " LITTLE GIANT'' DRILL 
IS THE STANDARD OF 
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RAND DRILL 
COMPANY 

128 BROADWAY, NEW YORK. 



ADVERTISEMENTS. 



1177 



INCERSOLL- 
SERCEANT 

AIR 

COMPRESSORS 




DUPLEX STEAM DRIVEN COMPOUND AIR COMPRESSOR, CLASS "g 

ROCK DRILLS 

QUARRYING 



MACHINERY 
COAL CUTTERS 



THE 



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CLEVELAND. OHIO 

CHICAGO. ILL. 

BOSTON. MASS. 

PITTSBURG. PA. 

PHILADELPHIA. PA. 

SALT LAKE CITY. UTAH. 
AND IN THE PRINCIPAL CITIES IN 
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INGERSOLL-SERGEANT ""T 



26 CORTLANDT STREET, N. Y. 



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ADVERTISEMENTS. 



■^ 



BROWN & SEWARD, 



SOLICITORS OF PATENTS AND 
EXPERTS IN PATENT CAUSES* 



26 J BROADWAY. 

NEW YORK, N. Y. 



V 



^^E have handled the patent interests of the most prominent 
individuals, firms and corporations for more than a quarter 
of a century* ^ t^ t^ ^ ^ 

Particular attention has been paid to the art of Air Com- 
pressors and we have been very extensively identified with 
its growth from the beginning of their practical use to the 
present time. ji jt jt ji ^ 



J 



FISKE BROTHERS REFINING CO. 



NON- 
CARBONIZING 



LUBROLEINE 
AIR <^ ^ t^ 
CYLINDER OIL 



For Use in Air Cylinders of Air Compressors 

Also all §frades of Lubricants for use on Machinery- 
propelled by Compressed Air and otherwise 



CABLE ADDRESS 
"LUBROLEINE" 

LONDON OFFICE 

9 New Broad St. 

London, E. C. 



50 MTater Street 
NE-W YORK, U. S. A, 

SOLE AGENTS FOR SCOTLAND 

John MacDonald & Son 
Glasgow 



J 



At>VERTISEMfiNtS. 



li?§ 



ALUS CHALMERS CO. 



SOLE BUILDERS OF 



REYNOLDS AIR COMPRESSORS 

AND BLOWING CNGINES. 




Two Stagfe Rledler Air Compressor driven by Cross-Compound Corliss Ens^ine, 
Built for Anaconda Copper Mining Co. 

SOLE BUILDERS OF 

RIEDLER AIR ^^ GAS 
COMPREvS^ORS. 




HOME INSURANCE BUILDING. 



ii8o ADVERTISEMENTS. 



The Westinghouse Air Brake Co. 

Manufacturers of 

Power Brake Equipments 

For All Classes of Service 

Steam and Motor-Driven Air Compressors 

Pneumatic and Electric Pump Governors 

General Office and Works: Wilmerding, Pa. 
New York Office: No. 1007 Havemeyer Building. 



Wheeler Condenser ^ Engineering Co., 

I20-2 Liberty St., NEW YORK. 
BRANCHES: Chicago. London. Paris. 

Manufacturers and Proprietors of 

Wheeler Surface Condenser. 

Wheeler Feed Water Heater. 

Wheeler Centrifugfal Pumps and Engfines. 
Edwards Patent Air Pump. 

Barnard-Wheeler Water Cooling: Towers, 
(Fan, Fanless Flue and Open Types.) 
Baker Patent Oil Separator. 
Wheeler Evaporators, Su§:ar Machinery and other Specialties. 



CATALOGUE AND INFORMATION ON APPLICATION. 



ADVERTISEMENTS. 



1181 




PNEUMATIC 

DRILLS. HAMMERS, HOISTS, RIVETERS, 

BLOW OFF COCKS, SPEED RECORDERS, 

BELL RINGERS 

and appliances of every description and highest grade. 



AIR COMPRESSORS 

BUILT IN ALL CAPACITIES. 



We install complete Air Plants assuming 
the entire Responsibility by Guaranteeing 
the complete outfit. 





Our tools have gained an enviable reputation everywhere due to 
the fact that they never disappoint. 

\^R,ITE FOR. CATALOGS. 




CHICAGO PNEUMATIC TOOL COMPANY 

aeNBRAL OFFICES, FISHER BUILDINQ, CHICAQO. 
EASTERN OFFICES, 95 LIBERTY ST., NEW YORK. 



iiSi 



ADVERTISEMENTS. 



Goodrich Rubber Goods, 




AIR, STEAM and WATER HOSE. 

FOR ALL PURPOSES. 



^ 



BELTING, PACKING, VALVES, GASKETS, 

RINGS, MATS, MATTING, 

RUBBER CARPET, MOLDED GOODS, ETC. 



TRADE MARK 

We will appreciate your inquiry for further information. 

The B. F. Goodrich Company 



AKRON RUBBER WORKS. 



J 
AKRON, OHIO. 



NEW YORK, BOSTON, CHICAGO, 

66 Keade Street. 157 Summer Street. 141 Lake Street. 

SAN FRANCISCO, 392 Mission Street. 



BALDWIN ACETYLENE MINE LAMPS. 



ABSOLUTELY 
SAFE. . . . 



Highly endorsed for 
use with Compressed 
Air Drills, etc. t^ ^ 




Cheaper than candles, 
electricity or oil. 



A. H. FUNKE, Manufacturer, 



Send for Catalogue, 
embracing testimoni- 
als from mines using 
them. J> J> ^ 



325 Broadway, 

IMENA/ YORK. 



ADVERTISEMENTS. 



1 183 



COOPER- 
CORLISS 
ENGINES 




FOR ALL POWER PURPOSES 



Complete Plants a Specialty 
EXCELLENT FACILITIES FOR HANDLING EXPORT TRADE 



ESTABLISHED 1833. 



m^C. & G. COOPER COMPANY 

MT. VERNON, OHIO, U. S. A. 




BRANCH OFFICES: 
NEW YORK 

1023 Ha vemeyer Building 
F. W. IREDELL, Managfer 

BOSTON 

411 Weld Buildins: 

B. A. CHURCH, Managfer 

ATLANTA ^^^ 

507 Gould Building: 

E. W. DUTTON, Manag:er 



II84 



ADVERTISEMENTS. 



AND n A C ^i"glB> Compound and Triple Steam; 



-A IK ^.^^ IjAo Single, Compound and Three Stage 

CU IVI ■ KLooUKo for air to every practicable pressure 

Gas Compressors for natural §:as and illuminating: g:as for railways. 



NORWALK IRON WORKS CO., south norwal k^conn. | 







8HEDD & SARLE, 

Engineers, 

146 Westminster St., Providence, R.I. 

■ 

Compressed Air. 
Water Power. . . 

Application of the principles of 
Pneumatics and Hydraulics 
to the practical develop- 
ment, and to the practical 
transmission of 
power. 


WE MAKE 

AIR 
DRILLS 

for Boring Coal, Rock 
Salt, Gypsum, etc. 

Send for Catalogs. 

Howells Mining Drill Co., 

Plymouth, Pa., U. S. A. 

Been at the business for twenty-five (25) years. 







LIDGERWOOD 



20,000 

IN USE 



HOISTING ENGINES 

and CABLEVbTAYS 

ThI world^ovIr 96 LIBERTY STREET, NEW YORK 



ADVERTISEMENTS. 



1 185 



DON'T WASTE 
COMPRESSED AIR 





SECTION— AMEW HOSE COUPLING. 



Send a Trial Order for 



SPRING STOP COCK. 



AMEW Hose Couplings 
AMEW Spring Stop Cocks 
AMEW Combined Valve and Oiler 

For controlling air supply to rock drills and oiling drills without disconnecting. 



AMERICAN ENGINEERING WORKS, 



CHICAQO, 
ILL, 



McKiernan Drill Co. 

170 BROADWAY, NEW YORK 

AIR COMPRESSORS 

For 
All 
Purposes 





SIMPLEST AND MOST 
ECONOMICAL 



ROCK 



DRILLS ^ 



SEND FOR CATALOGUE 




ii86 


ADVERTISEMENTS. 


' 


1 


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HEAT YOUR RIVETS 


"M 




WITH 






OIL 


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CHEAPER 


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QUICKER 


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BETTER 




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WE ALSO HAVE 


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FOR EVERY PURPOSE 


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NEW YORK 



AIR COMPRESSORS 



OF EVERY TYPE 



AIR RECEIVERS CARBONIC ACID GAS PUMPS 

VACUUM PUMPS AIR LIFT PUMPING SYSTEM 

AIR HOISTS ji ^ ^ ^ ^ 

COMPRESSED AIR TOOLS AND APPLIANCES 



AMERICAN AIR COMPRESSOR WORKS 

26 Cortlandt St., NEW YORK CITY 



Cable Address Fairhurst- 



ADVERTISEMENTS. 



1187 



"Compressed Air'* 

Published Monthly. 

This is the only publication devoted to the useful application of compreeeed 
air, and it is the recognized authority on all matters pertaining to this subject. 



RAT:^S OF" SUBSCRIPTION, 

United States, Canada and Mexico, 
All other Countries, 
Single Copies, 



per year, $1.00 
1.50 

.JO 



SPMCIAI,. 

Clubs of ten subscribers. , ..... 

The attention of Engineeis, Superintendents, Railroad Master Mechanics, 
Manufacturers of Compressed Air Appliances, Students, and all others 
whose association with compressed air require the widest knowledge of the 
application of air power is called to this Special Rate. It enables them 
to place the magazine in the hands of operators of compressed air 
apparatus by club subscriptions at an extremely low cost. 

I,IST OF BOOKS ON COMPRJ^SS^D AIR. 

Volume No. 6, Compressed Air," •••... cloth, 

March, 1901— February, IQOSS, inclusive. The twelve numbers of 
"Compressed Air," which make up this volume are profusely illustrated 
with fine half-tone engravings and line cuts of a large number of important 
applications of compressed air. 

"Compressed Air Production," by W. L. Saunders, .... cloth. 

Compressed Air Production or The Theory and Practice of Air Compression. 
By W. L. Saunders. A practical treatise on air compression and com- 
pressed air machinery. It contains rules, tables and data of value to 
engineers. 

" Pumping by Compressed Air," by Edward A. Rix, .... 

A practical treatise on this subject, containing valuable information, with 
diagrams and tables. The different systems are described and compared, 
and the advantages of each impartially stated. 

" Compressed Air," by Frank Richards, . . . , cloth. 

Compressed Air, by Prank Richards. Contains practical information upon air 
compression and the transmission and application of compressed air. 

"Liquid Air and the Liquefaction of Gases," by Prof. T.O'ConorSloane, 350 pages, 

Expesiments upon the Transmission of Power by Compressed Air in Paris, by A. 
B. W. Kennedy, F. R. S., M. Inst. C. E., Emeritus Professor of Engineering in 
University College, London. The Transmission and Distribution of Power 
from Central Station by Compressed Air, by William Cawthorne Unwin. B. 
8. C, F. R. S., M. Inst. C.E., 



5'00 



The Transmission of Power by Compressed Air, by Robert Zahner, M. E., 

"Tunneling," a practical treatise, by Charles Prelini, C 
Charles S. Hill, C. E. 150 diagrams and illustrations. 



With additions by 
cloth. 



" Transmiasion of Power by Fluid Pressure," by Wm. Donaldson, M. A. 

(M. Inst. C. E.) 

Forwarded postpaid on receipt of price. 



cloth, 



• 75 



1.50 



2.50 



'SO 
•50 



3.00 
a. 45 



n 



COMPRESSMD AIR/' »6 cortlandt st., nf:w york. 



ii88 



ADVERTISEMENTS. 



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